1. A process for additive manufacturing and refurbishment of High-Strength Low-Alloy (HSLA) components, comprising: a. depositing HSLA filler wire in a layer-by-layer method using a Wire Arc Additive Manufacturing (WAAM) process to build a structure; b. forming grooves on a top surface of each deposited layer; c. introducing a predetermined quantity of tungsten carbide (WC) powder onto the top surface comprising the grooves; d. depositing a subsequent layer of HSLA filler material over the WC powder to embed WC particles within a matrix; and e. repeating steps (b) to (d) during layer-wise deposition to produce a wear-resistant or refurbished HSLA component or region thereof having increased hardness, enhanced wear resistance, and durability.

2. The process as claimed in claim 1, wherein the WAAM process is performed using a metal inert gas (MIG) welding process.

3. The process as claimed in claim 1, wherein the HSLA filler wire comprises ER100SG, ER110SG, ER120SG, or an equivalent high-strength low-alloy steel wire having a tensile strength of at least about 100 ksi.

4. The process as claimed in claim 1, wherein the tungsten carbide (WC) powder is added in a controlled proportion ranging from 5 wt.% to 15 wt.% relative to the deposited layer weight.

5. The process as claimed in claim 1, wherein the grooves are of predefined geometry including diamond shape to facilitate retention and uniform distribution of the WC powder.

6. The process as claimed in claim 5, wherein the grooves have dimensions of about 6 mm × 6 mm and are oriented at about 45 degrees.

7. The process as claimed in claim 1, wherein the WC powder is spread over the top surface and the grooves retain at least a portion of the WC powder during deposition of the subsequent layer.

8. The process as claimed in claim 1, wherein the WC powder has a particle size ranging from 40 µm to 50 µm, substantially spherical morphology, and a purity of about 99%.

9. The process as claimed in claim 1, wherein a weight of each deposited layer is determined from the layer volume and density of the HSLA filler wire, and the predetermined quantity of WC powder is calculated based on the determined layer weight.

10. The process as claimed in claim 9, wherein the WC powder is added in an amount of about 1.5 g, 3.5 g, or 5.0 g per layer corresponding respectively to about 5 wt.%, 10 wt.%, or 15 wt.% relative to the deposited layer weight.

11. The process as claimed in claim 1, wherein the WAAM process is performed using a current of 140 A to 160 A, a travel speed of 9 mm/s to 11 mm/s, a shielding gas flow rate of 18 L/min to 20 L/min, a tip-to-workpiece distance of 15 mm to 18 mm, and a layer thickness of 1.8 mm to 2.2 mm.

12. The process as claimed in claim 1, wherein the grooves are formed manually by grinding or automatically by a CNC-based end-milling attachment integrated with the WAAM setup.

13. The process as claimed in claim 1, wherein the WC powder is introduced manually or by a hopper-and-nozzle powder delivery system.

14. The process as claimed in claim 1, wherein the subsequent deposition establishes metallurgical bonding and forms carbide phases including WC and/or W₂C within the HSLA matrix.

15. An additively manufactured or refurbished high-strength low-alloy (HSLA) component obtained by a process comprising: a. depositing HSLA filler wire in a layer-by-layer method using a WAAM process; b. forming grooves on a top surface of each deposited layer; c. introducing a predetermined quantity of tungsten carbide (WC) powder onto the top surface comprising the grooves; d. depositing a subsequent layer of HSLA filler material over the WC powder to embed WC particles within a matrix; and e. repeating steps (b) to (d) during layer-wise deposition to form an additively manufactured, refurbished, or wear-resistant region of the HSLA component, wherein the additively manufactured, refurbished, or wear-resistant region comprises a plurality of high-strength low-alloy steel layers deposited by the WAAM process and tungsten carbide particles incorporated between adjacent deposited layers in an amount ranging from 5 wt.% to 15 wt.% relative to the deposited layer weight.

16. The additively manufactured or refurbished HSLA component as claimed in claim 15, wherein the additively manufactured, refurbished, or wear-resistant region comprises tungsten carbide and ditungsten carbide phases distributed in an iron-based matrix and exhibits increased hardness and wear resistance relative to a corresponding HSLA region without tungsten carbide incorporation.

17. The additively manufactured or refurbished HSLA component as claimed in claim 15 or claim 16, wherein the additively manufactured, refurbished, or wear-resistant region comprises about 5 wt.% to 15 wt.% tungsten carbide relative to the deposited layer weight and exhibits a Vickers microhardness in a range of about 558.5 HV0.5 to 826.2 HV0.5.

Description:
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

A PROCESS FOR ADDITIVE MANUFACTURING AND REFURBISHMENT OF HIGH-STRENGTH LOW-ALLOY (HSLA) COMPONENTS AND COMPONENTS THEREFROM

TECHNOLOGY INNOVATION IN EXPLORATION & MINING FOUNDATION
a company incorporated in India, having address at
3rd Floor, i2h Tower (Institute Innovation Hub), IIT(ISM) Dhanbad, Jharkhand - 826004

The following specification particularly describes the invention and the manner in which it is to be performed.
 
FIELD OF THE INVENTION
The embodiments of the subject matter described in this specification relate to a process for additive manufacturing and refurbishment of High-Strength Low-Alloy (HSLA) components and components therefrom.

BACKGROUND OF THE INVENTION
Heavy industrial components are often exposed to wear, corrosion, and related service conditions during operation, which may adversely affect their surface condition, dimensional integrity, and service life. Components used in mining, marine, defence, and other heavy-duty applications may therefore require repair, rebuilding, or localized reinforcement after prolonged use.
High-strength low-alloy (HSLA) steels are used for such components because of their combination of strength, toughness, and reliability. HSLA filler wires, such as ER100SG wire, may be used in wire arc additive manufacturing (WAAM) for forming or rebuilding metallic structures. WAAM is a layer-wise deposition process that uses an electric arc as a heat source and a metal wire as feedstock, and is considered suitable for manufacture and repair of relatively large or near-net-shape metallic components.
It is also known that tungsten carbide (WC) is a hard material having favorable hardness, thermal stability, and wear-resistance characteristics. Incorporation of WC into steel-based systems has been considered for improving hardness and wear-related performance of deposited or repaired regions.
However, in the case of HSLA components, a need remains for a process that enables additive manufacturing and refurbishment using HSLA filler wire together with controlled incorporation of WC during WAAM deposition. A need further exists for a process in which WC may be introduced between deposited HSLA layers so as to improve hardness, wear resistance, and durability of the resulting region.
A further need exists for a process suitable for relatively large industrial components, while allowing localized build-up, reduced material wastage, and dimensional restoration of the component. Accordingly, there remains a need for a WAAM-based process for additive manufacturing and refurbishment of HSLA components with layer-wise incorporation of WC reinforcement.
Accordingly, it is an object of the present invention to address one or more of the aforementioned issues.

SUMMARY OF THE INVENTION
A process for additive manufacturing and refurbishment of High-Strength Low-Alloy (HSLA) components, comprising: a. depositing HSLA filler wire in a layer-by-layer method using a Wire Arc Additive Manufacturing (WAAM) process to build a structure; b. forming grooves on a top surface of each deposited layer; c. introducing a predetermined quantity of tungsten carbide (WC) powder onto the top surface comprising the grooves; d. depositing a subsequent layer of HSLA filler material over the WC powder to embed WC particles within a matrix; and e. repeating steps (b) to (d) during layer-wise deposition to produce a wear-resistant or refurbished HSLA component or region thereof having increased hardness, enhanced wear resistance, and durability.

BRIEF DESCRIPTION OF DRAWINGS
Reference will be made to embodiments of the invention, example of which may be illustrated in the accompanying figure(s). These figure(s) are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows a schematic diagram of an experimental process according to an embodiment of the present invention.
Figure 2 shows an overall flow chart of the process according to an embodiment of the present invention.
Figure 3 shows an elemental distribution of WAAM deposited structures having varying wt.% of WC powder according to an embodiment of the present invention.
Figure 4 shows an XRD analysis of WAAM fabricated samples according to an embodiment of the present invention.
Figure 5 shows average microhardness of deposited structures according to an embodiment of the present invention.
Figure 6 shows wear rate of deposited structures under varying loads according to an embodiment of the present invention.
Figure 7 shows coefficient of friction of deposited structures with respect to time under varying loads according to an embodiment of the present invention.
Figure 8 shows wear track surface roughness under varying loads according to an embodiment of the present invention.
Figure 9 shows wear track surface condition under varying loads for deposited structures according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention are described herein. The following detailed description sets forth illustrative embodiments in sufficient detail to enable a person having ordinary skill in the art to make and use the invention and to clearly understand the same. However, the detail provided is not intended to limit the scope of the invention. Rather, the invention is intended to cover all modifications, equivalents, variations, and alternatives that would be apparent to a person having ordinary skill in the art and that fall within the spirit and scope of the invention as defined by the appended claims.
As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Further, as used herein, the term “in” is intended to include both “in” and “on” unless the context clearly dictates otherwise. The term “comprising” is intended to be open-ended and means including, but not limited to. Unless expressly stated otherwise, the sequence of steps described herein is not intended to be limiting. Features described in connection with one embodiment may be used alone or in combination with features of other embodiments unless such combination is technically incompatible. Where a range of values is disclosed, all individual values and sub-ranges within that range are intended to be encompassed. Without limiting the scope of the appended claims, the present specification sets forth illustrative embodiments, including the best method presently known to the applicant for performing the invention and for which protection is sought. The present disclosure is intended to enable a person having ordinary skill in the art to make and use the invention, while encompassing modifications, equivalents, variations, and alternatives consistent with the present disclosure and within the spirit and scope of the appended claims.
In some embodiments, the invention provides a process for additive manufacturing and refurbishment of High-Strength Low-Alloy (HSLA) components. The process may include depositing HSLA filler wire in a layer-by-layer method using a Wire Arc Additive Manufacturing (WAAM) process to build a structure. Grooves may be formed on a top surface of each deposited layer, following which a predetermined quantity of tungsten carbide (WC) powder may be introduced onto the top surface comprising the grooves. A subsequent layer of HSLA filler material may then be deposited over the WC powder so as to embed WC particles within a matrix. The groove formation, WC powder introduction, and subsequent deposition steps may be repeated during layer-wise deposition to produce a wear-resistant or refurbished HSLA component or region thereof having increased hardness, enhanced wear resistance, and durability.
In some embodiments, the WAAM process may be performed using a metal inert gas (MIG) welding process. In some embodiments, the HSLA filler wire may comprise ER100SG, ER110SG, ER120SG, or an equivalent high-strength low-alloy steel wire having a tensile strength of at least about 100 ksi. In some embodiments, the WC powder may be added in a controlled proportion ranging from 5 wt.% to 15 wt.% relative to the deposited layer weight.
In some embodiments, the grooves may be of predefined geometry, including diamond shape, to facilitate retention and uniform distribution of the WC powder. In some embodiments, the grooves may have dimensions of about 6 mm × 6 mm and may be oriented at about 45 degrees. In some embodiments, the WC powder may be spread over the top surface, while the grooves retain at least a portion of the WC powder during deposition of the subsequent layer.
In some embodiments, the WC powder may have a particle size ranging from 40 µm to 50 µm, substantially spherical morphology, and a purity of about 99%. In some embodiments, a weight of each deposited layer may be determined from the layer volume and density of the HSLA filler wire, and the predetermined quantity of WC powder may be calculated based on the determined layer weight. In some embodiments, the WC powder may be added in an amount of about 1.5 g, 3.5 g, or 5.0 g per layer corresponding respectively to about 5 wt.%, 10 wt.%, or 15 wt.% relative to the deposited layer weight.
In some embodiments, the WAAM process may be performed using a current of 140 A to 160 A, a travel speed of 9 mm/s to 11 mm/s, a shielding gas flow rate of 18 L/min to 20 L/min, a tip-to-workpiece distance of 15 mm to 18 mm, and a layer thickness of 1.8 mm to 2.2 mm. In some embodiments, the grooves may be formed manually by grinding or automatically by a CNC-based end-milling attachment integrated with the WAAM setup. In some embodiments, the WC powder may be introduced manually or by a hopper-and-nozzle powder delivery system. In some embodiments, the subsequent deposition may establish metallurgical bonding and may form carbide phases including WC and/or W₂C within the HSLA matrix.
In some embodiments, the invention also provides an additively manufactured or refurbished high-strength low-alloy (HSLA) component obtained by the above process. The component may include an additively manufactured, refurbished, or wear-resistant region formed by repeated layer-wise deposition, groove formation, WC powder introduction, and subsequent deposition of HSLA filler material over the WC powder. In some embodiments, the additively manufactured, refurbished, or wear-resistant region may comprise a plurality of high-strength low-alloy steel layers deposited by the WAAM process and tungsten carbide particles incorporated between adjacent deposited layers in an amount ranging from 5 wt.% to 15 wt.% relative to the deposited layer weight. In some embodiments, such region may further comprise tungsten carbide and ditungsten carbide phases distributed in an iron-based matrix and may exhibit increased hardness and wear resistance relative to a corresponding HSLA region without tungsten carbide incorporation. In some embodiments, the region may comprise about 5 wt.% to 15 wt.% tungsten carbide relative to the deposited layer weight and may exhibit a Vickers microhardness in a range of about 558.5 HV0.5 to 826.2 HV0.5.
According to some embodiments of the present invention, to conduct this experiment for development of the process, a 6-axis ABB IRB1520ID robot with MIG is utilized to deposit with the HSLA (ER100SG) filler wire (1.2 mm) on the MS substrate (Table 1), which was cleaned by acetone before starting the experiment.
In some embodiments, wires such as ER110SG and ER120SG, or equivalent HSLA wires having tensile strength greater than about 100 ksi, may also be used. Here, ER means it is electrode, 100 means 100,000 psi of tensile strength, S means solid wire, and G means it is low alloy steel. In industrial refurbishment, HSLA components are commonly rebuilt, although MS or SS substrates of any grade may be used where the substrate is not part of the final component. If the substrate forms an integral part of the component, an HSLA substrate is preferably selected to ensure compatibility with HSLA deposition. The deposition process is done with the two optimum parameters (current 150 A and travel speed 10 mm/s) as per the best bead geometry with followed by the square deposition strategy.
In some embodiments, the working process window may include a current of 140-160 A, a travel speed of 9-11 mm/s, a shielding gas flow rate of 18-20 L/min, a tip-to-workpiece distance of 15-18 mm, and a layer thickness of 1.8-2.2 mm. A pure Argon shield (18 L/min) gas is used to protect the molten pool from oxidation. A constant tip-to-workpiece distance of 16 mm was maintained at the time of deposition. After depositing a complete layer, the diamond shaped (6 mm × 6 mm, 45° angle) grooves were cut with a hand grinder on the top surface as shown in Fig. 1. In the present experimental study, groove formation was performed manually; however, groove formation may also be automated within the WAAM setup using a CNC-based end-milling attachment mounted on the same robotic arm or as a synchronized secondary tool head. Then, the WC powder particles were spread around the top the surface and the created grooves were utilized to trap the powders by overcoming the arc pressure. Alternatively, a hopper-and-nozzle system may be used for powder delivery. WC is used in the present work due to its favorable material characteristics, particularly its high density of about 14-15 g/cm3, which facilitates effective settling and stable retention within the molten pool; alternative carbide reinforcements are not considered within the present work. Then again, another layer was deposited, and the WC powder mixed and get well distributed in the deposited materials. The process was repeated to fabricate the required dimension of the part (20 mm height and 40 mm X 40 mm cross section). Three different weight percentage of WC powder (5 %,10 %,15 %) were considered and finally four HSLA fabricated structures were prepared for further analysis (inclusion of one without the addition of WC powder). Each deposited ER100SG layer volume is calculated by Eq 1. According to the layer volume WC wt% is calculated by Eq 2. All the samples were extracted from the substrate using an automatic horizontal band saw. Then the blocks are sliced with 15mm x 15mm, and 8mm thick with a WEDM machine for tribological reciprocating wear tests, which was carried out by Universal tribometer (Rtec Instruments USA MFT 5000) with a WC ball (6mm dia) and varying three different loads (20N, 30N, 40N) with the fixed sliding distance is 500m. The coefficient of friction (COF) is measured by MFT 18 R4C software with respect to total wear time. A fixed frequency of 8Hz was chosen for all the combinations of wear track (ASTM-G133). All combination of samples were polished, followed by the standard method (grid paper and cloth). The hardness test was performed (before wear track) for four combinations of fabricated structures by a Vickers hardness tester (Mitutoyo, Japan) with a 500g load, and the dwell time is 10s. The wear track’s surface was analyzed by a non-contact type 3D profilometer (Zygo, 9000, US), and surface morphology was characterized using A field emission scanning electron microscope FESEM (SIGMA 300, Zeiss, Germany). The elemental distribution was also characterized using energy dispersive spectroscopy (EDS), which is integrated with the FESEM. The overall flow chart of this innovation is shown in Fig. 2 for clear and better understanding.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention. The drawings are illustrative only and are not intended to limit the scope of the invention. Like reference numerals generally refer to like elements throughout the several views, unless the context clearly indicates otherwise. The drawings are not necessarily to scale, and certain features may be exaggerated, simplified, or omitted for clarity. Any directional terms used with reference to the drawings are used solely for convenience of description and are not intended to require any particular orientation unless expressly stated otherwise. Reference numerals are included solely to facilitate understanding and are not intended to limit the scope of the claims. Where the drawings include flowcharts, block diagrams, or process illustrations, the depicted sequence is illustrative unless expressly stated otherwise.
Referring to Figure 1, a schematic diagram of an experimental process according to an embodiment of the present invention is illustrated.
The Eqs. are listed below.
Each layer volume = 40x40x2 mm3 = 3200 mm3 = 3.2 cm3 (1)
Layer weight = Layer vol. x density of wire =3.2cm3 x 7.7gm/cm3 = 24.64 = 25 gm (app) (2)
Based on the calculated layer weight of about 25 gm, the amount of WC powder added per layer was determined relative to the weight of each deposited layer. In particular, about 1.5 gm WC powder was used for 5 wt.% addition, about 3.5 gm WC powder was used for 10 wt.% addition, and about 5.0 gm WC powder was used for 15 wt.% addition.
According to an embodiment of the present invention, the WC powder had a particle size range of 40-50 µm, substantially spherical morphology, and purity of about 99%. To achieve uniform distribution of WC powder, the measured quantity of WC powder was evenly spread over the deposited layer before deposition of the next layer, and the weight of each deposited layer was measured to ensure that the WC content remained within the specified range of 5-15 wt.% for every layer.
Table 1. Chemical composition of ER100SG wire, substrate and powder
Wt% C Mn Si S P Cu Cr Ni Fe W
ER 70S 6 (substrate) 0.141 1.45 0.812 0.18 0.024 0.083 0.02 0.03 Bal --
ER 100SG (wire) 0.08 1.60 0.500 0.009 0.005 0.150 0.30 1.50 Bal --
WC powder 6.18 0.001 0.001 0.001 0.001 0.0003 0.005 -- 0.15 Bal

Referring to Figure 2, an overall flow chart of the process according to an embodiment of the present invention is illustrated.
Referring to Figure 3, elemental distribution of WAAM deposited structures having varying wt.% of WC powder according to an embodiment of the present invention is illustrated. Referring to Fig. 3, elemental distribution of four WAAM-deposited structures with varying wt.% of WC powder is illustrated according to an embodiment of the present invention, wherein: (a) 0% WC, (b) 5% WC, (c) 10% WC, and (d) 15% WC.
Fig 3 shows the elemental distribution of four different WAAM deposited structures according to the increment of wt% of WC powder. However, without the addition of WC powder (0% WC) structure showed the highest Fe wt% (95.64) amongst the whole element. After adding the 5% WC, the wt% of W (4.59), it confirms WC particle is well distributed in the surface, however, Fe wt% (90.60) is decreased compared to the 0% WC structure. The 10% WC structure denoted that the wt% of W (8.19), which also confirms WC particle is well distributed. Lastly, the 15% WC structure showed wt% of W (13.29), which confirms again the WC particle well distributed. Therefore, it can be concluded that in all WC particle adding structures, the WC powder is fine distributed in between every deposited two layers of the fabricated structure. Therefore, W and C diffuse into Fe, which enhances the hardness and increasing the wt% of WC particles hardness is also increased.
Referring to Figure 4, XRD analysis of WAAM fabricated samples according to an embodiment of the present invention is illustrated.
The HSLA fabricated structure without WC powder and along with the addition of 5%, 10%, and 15% wt respectively of WC particle structure further used for peak analysis by XRD test. The Fig 4 shows that the peak of α-Fe (BCC) is present for all combinations of samples in 44.73° {011}, 64.07°{020}, and 82.43°{121} with different intensities. Because additional WC formed carbide, and the crystal structure is changed into martensite structure (possibility). In this condition, the BCC pack's intensity is lower due to the generation of residual stress and lattice distortion. After that, the addition of WC particle with wt% (5, 10, 15) shows WC {110} and W2C {111} formation, when WC% increased 5-10%, then WC {110} and W2C {111} peaks are clearly visible. Though 15%WC shows less formation of WC phase, due to WC particles decomposing into W and C (WC → W + C), and lattice strain and microstructural refinement induced by the thermal cycles of the WAAM process. These phases also balance between hardness, toughness, and provide more wear resistance. On the other hand, high thermal stability and chemical motionlessness are maintained by WC and W₂C, which is necessary to repair the wear-resistant heavy components in industry.
Referring to Figure 5, average microhardness of deposited structures according to an embodiment of the present invention is illustrated.
The average micro hardness of four samples (0% WC, 5% WC, 10% WC, 15% WC) is shown in Fig 5. It can be seen that without the addition of WC powder fabricated structure micro hardness is the lowest (274.95 HV0.5) among all structures. The basic reason is that it consists of ferrite and pearlite phases typical of mild steel. Therefore, the microstructure is relatively soft and ductile, with no hard reinforcing particles present. The absence of any carbide phase results in minimal resistance to indentation. The rest of the WC powder added structures show that the hardness is correspondingly increased with the increase of wt% of WC particle. The hardness value is 558.5 HV0.5 for 5% WC, 650.6 HV0.5 for 10% WC, and 826.2 HV0.5 for 15% WC structure. The addition of WC powder introduces hard WC particles within the iron matrix. During the WAAM process, partial dissolution of WC occurs due to the high arc temperature, forming secondary hard phases such as WC, W₂C, which act as strengthening sites. The dispersed carbides hinder dislocation motion, leading to enhanced hardness. Though WC is an extremely hard ceramic compound and harder than MS. It resists indentation, plastic deformation, and resists grain growth during solidification. Though more wt% of WC creates microcracks, due to the thermal expansion mismatch. Whereas, WC has a lower thermal expansion coefficient than MS. During cooling, uneven contraction generates residual stresses, causing microcracks at WC-MS interfaces and increased brittleness, from the past study it can be concluded. Therefore, in this innovation, 5-15% wt of WC particle is added with deposition of ER100SG wire by the WAAM process to increase the hardness of the wear-resistant components.
Referring to Figure 6, wear rate of deposited structures under varying loads according to an embodiment of the present invention is illustrated.
The dry reciprocating tribological wear test reveals that (Fig 6) the wear rate of a 15% WC block with 30N load offers the minimum wear rate among all (1.29 x10-7 mm3/N-m). The wear is calculated by the Eq (3). Lower wear signifies a refined and harder microstructure, indicating proper bonding between layers and reduced porosity. It confirms that reinforcement additives (WC, W2C particles) effectively enhanced the hardness and load-bearing capability. On the other hand, it increases the service life of heavy components. However, Fig 7 describes that the coefficient of friction (COF) with respect to time is minimum for a 15% WC block with all combinations of load. Though without adding the WC particle shows minimum COF, however, this structure's (0% WC) hardness and wear rate are very poor, which has already described. The COF is controlled by two competing mechanisms, adhesive sliding at metal-to-metal contacts and abrasive or ploughing contributions from hard WC particles and debris. However, excessively high wt% of WC particle increases the particle protrusion, fracture, and pull-out, which produces hard debris that enhances ploughing, which raises of COF. Higher loads increase the real contact area and penetration of hard particles, amplifying ploughing and particle fracture.
Wear rate = Net volume of track / (sliding distance*load) mm3/N-m (3)
Referring to Figure 7, coefficient of friction of deposited structures with respect to time under varying loads according to an embodiment of the present invention is illustrated.
The wear track surface analysis according to some embodiments of the present invention:
After the wear test, the track surface roughness (Ra) is measured (Fig 8), and Ra is minimum (0.272 μm) when applied 30N load for 15% WC block. This is much better than without adding the WC particle structure. The main cause is that increasing the WC particle raises surface hardness and reduces plastic deformation and ploughing, which offers lower surface roughness at moderate load. Therefore, increasing the normal load increases contact stress and promotes deeper ploughing and subsurface cracking; whether roughness rises. An image (Fig 9) of the wear track showed that without adding the WC particle, grooves and debris are clearly visible. Also, the quantity of debris is too less for the WC-added structure compared to without the addition of WC particle structure. When wt% of WC particle is increased, the groves are less visible and less debris is present for all combinations of loads. The formation of debris is due to the action of adhesion between asperities and considerable plastic deformation of asperities caused during sliding motion. The high wear loss in the initial stages was possibly due to high localised contact pressure at the real contact point between the opposing asperities.
Referring to Figure 8, wear track surface roughness under varying loads according to an embodiment of the present invention is illustrated.
Referring to Figure 9, wear track surface condition under varying loads for deposited structures according to an embodiment of the present invention is illustrated.
In some embodiments, the present invention further provides an additively manufactured or refurbished high-strength low-alloy (HSLA) component obtained by the process described herein. More particularly, by depositing HSLA filler wire in a layer-by-layer manner using the WAAM process, forming grooves on a top surface of each deposited layer, introducing a predetermined quantity of tungsten carbide (WC) powder onto the top surface comprising the grooves, depositing a subsequent layer of HSLA filler material over the WC powder to embed WC particles within a matrix, and repeating the groove-forming, WC-introducing, and subsequent deposition steps during layer-wise deposition, an additively manufactured, refurbished, or wear-resistant region may be formed in the HSLA component.
In some embodiments, the additively manufactured, refurbished, or wear-resistant region comprises a plurality of high-strength low-alloy steel layers deposited by the WAAM process and tungsten carbide particles incorporated between adjacent deposited layers in an amount ranging from 5 wt.% to 15 wt.% relative to the deposited layer weight. As described above with reference to the process embodiments and the corresponding figures, such interlayer incorporation of WC particles may be achieved by introducing WC powder onto the deposited layer and retaining at least a portion of the powder during subsequent deposition, thereby forming a reinforced HSLA region.
In some embodiments, the additively manufactured, refurbished, or wear-resistant region comprises tungsten carbide and ditungsten carbide phases distributed in an iron-based matrix and exhibits increased hardness and wear resistance relative to a corresponding HSLA region without tungsten carbide incorporation. In some embodiments, the additively manufactured, refurbished, or wear-resistant region comprises about 5 wt.% to 15 wt.% tungsten carbide relative to the deposited layer weight and exhibits a Vickers microhardness in a range of about 558.5 HV0.5 to 826.2 HV0.5.
INDUSTRIAL APPLICABILITY, AND ECONOMIC SIGNIFICANCE
The present invention is industrially applicable not only as a process for additive manufacturing and refurbishment of HSLA components, but also in relation to the resulting additively manufactured or refurbished HSLA components having reinforced wear-resistant regions formed by interlayer incorporation of tungsten carbide particles.
The heavy machinery components of HSLA can be easily repaired and enhanced to improve their mechanical properties, particularly hardness, wear resistance, as well as enhanced the life span of the components. It can be done only with the WAAM process and using HSLA wire with the addition of WC powder in between two deposited layers. Another benefit is, the process can be customized as per the user requirements and the post-processing treatments, the cost is minimal. However, the total process also minimizes the material wastage.
This invention introduces a novel approach for repairing the heavy machinery components by improving the mechanical properties and durability using by WAAM process with the addition of tungsten carbide (WC) powder into HSLA wire. This kind of WAAM process has never been explored previously. This powder addition process enhanced the hardness upto 66% and improved the wear resistance by 2.4 times of HSLA-made heavy industrial components compared to without the addition of WC powder structure. Furthermore, the WC particle addition process decreased the surface roughness of the wear track (77.4%) and reduced the debris compared to without adding the WC structure. Therefore, these conditions enhance the life cycle of machinery components. The existing methods, like cladding or plasma process, cannot provide a quick repairing process and cannot able to customize as per the industry requirements. Also, the existing process is not suitable for repairing the heavy, large size machining components and cannot able to maintain the proper dimensional accuracy. Therefore, only the WAAM process is a suitable method for solving the whole phenomenon smoothly and precisely.
The invention is more economical than existing technologies such as thermal spray coating, laser cladding, or complete part replacement.
The present invention is industrially applicable to the additive manufacturing, repair, and refurbishment of HSLA components, particularly components subjected to wear in heavy-duty service environments. Economically, the invention may provide advantages over conventional approaches. Complete component replacement generally involves very high material and machining costs, whereas refurbishment in accordance with the present invention may reduce the total cost by about 50–70%. Thermal spray coating, although moderate in cost, may be limited by poor adhesion and restricted coating thickness; in contrast, the present invention may provide strong metallurgical bonding and permit formation of thicker reinforced regions. Laser cladding is generally associated with high equipment cost and limited deposition rate, whereas the WAAM-based process disclosed herein may provide higher deposition rate at lower cost. Accordingly, the present invention, employing WAAM with WC reinforcement, may provide a low-to-moderate-cost and industrially practical route for achieving cost-effective repair together with tuneable hardness and improved wear performance.
The foregoing description is illustrative of the principles of the present invention and is not intended to be exhaustive or to limit the invention to the specific embodiments disclosed. A person having ordinary skill in the art will appreciate that the conception disclosed herein may be readily used as a basis for making, using, modifying, adapting, or designing other embodiments, arrangements, and structures for carrying out the same or similar purposes of the present invention. It will also be appreciated that various changes, substitutions, modifications, and alternative arrangements may be made without departing from the spirit and scope of the present invention, even though such variations may not be expressly described or illustrated herein. The examples set forth herein are provided solely for illustrative purposes and are not intended to limit the invention to the specific examples, conditions, or embodiments disclosed. Accordingly, the scope of the present invention is defined by the appended claims and encompasses all modifications, equivalents, and alternatives falling within the spirit and scope thereof.
, Claims:I/We claim:
1. A process for additive manufacturing and refurbishment of High-Strength Low-Alloy (HSLA) components, comprising:
a. depositing HSLA filler wire in a layer-by-layer method using a Wire Arc Additive Manufacturing (WAAM) process to build a structure;
b. forming grooves on a top surface of each deposited layer;
c. introducing a predetermined quantity of tungsten carbide (WC) powder onto the top surface comprising the grooves;
d. depositing a subsequent layer of HSLA filler material over the WC powder to embed WC particles within a matrix; and
e. repeating steps (b) to (d) during layer-wise deposition to produce a wear-resistant or refurbished HSLA component or region thereof having increased hardness, enhanced wear resistance, and durability.
2. The process as claimed in claim 1, wherein the WAAM process is performed using a metal inert gas (MIG) welding process.
3. The process as claimed in claim 1, wherein the HSLA filler wire comprises ER100SG, ER110SG, ER120SG, or an equivalent high-strength low-alloy steel wire having a tensile strength of at least about 100 ksi.
4. The process as claimed in claim 1, wherein the tungsten carbide (WC) powder is added in a controlled proportion ranging from 5 wt.% to 15 wt.% relative to the deposited layer weight.
5. The process as claimed in claim 1, wherein the grooves are of predefined geometry including diamond shape to facilitate retention and uniform distribution of the WC powder.
6. The process as claimed in claim 5, wherein the grooves have dimensions of about 6 mm × 6 mm and are oriented at about 45 degrees.
7. The process as claimed in claim 1, wherein the WC powder is spread over the top surface and the grooves retain at least a portion of the WC powder during deposition of the subsequent layer.
8. The process as claimed in claim 1, wherein the WC powder has a particle size ranging from 40 µm to 50 µm, substantially spherical morphology, and a purity of about 99%.
9. The process as claimed in claim 1, wherein a weight of each deposited layer is determined from the layer volume and density of the HSLA filler wire, and the predetermined quantity of WC powder is calculated based on the determined layer weight.
10. The process as claimed in claim 9, wherein the WC powder is added in an amount of about 1.5 g, 3.5 g, or 5.0 g per layer corresponding respectively to about 5 wt.%, 10 wt.%, or 15 wt.% relative to the deposited layer weight.
11. The process as claimed in claim 1, wherein the WAAM process is performed using a current of 140 A to 160 A, a travel speed of 9 mm/s to 11 mm/s, a shielding gas flow rate of 18 L/min to 20 L/min, a tip-to-workpiece distance of 15 mm to 18 mm, and a layer thickness of 1.8 mm to 2.2 mm.
12. The process as claimed in claim 1, wherein the grooves are formed manually by grinding or automatically by a CNC-based end-milling attachment integrated with the WAAM setup.
13. The process as claimed in claim 1, wherein the WC powder is introduced manually or by a hopper-and-nozzle powder delivery system.
14. The process as claimed in claim 1, wherein the subsequent deposition establishes metallurgical bonding and forms carbide phases including WC and/or W₂C within the HSLA matrix.
15. An additively manufactured or refurbished high-strength low-alloy (HSLA) component obtained by a process comprising:
a. depositing HSLA filler wire in a layer-by-layer method using a WAAM process;
b. forming grooves on a top surface of each deposited layer;
c. introducing a predetermined quantity of tungsten carbide (WC) powder onto the top surface comprising the grooves;
d. depositing a subsequent layer of HSLA filler material over the WC powder to embed WC particles within a matrix; and
e. repeating steps (b) to (d) during layer-wise deposition to form an additively manufactured, refurbished, or wear-resistant region of the HSLA component,
wherein the additively manufactured, refurbished, or wear-resistant region comprises a plurality of high-strength low-alloy steel layers deposited by the WAAM process and tungsten carbide particles incorporated between adjacent deposited layers in an amount ranging from 5 wt.% to 15 wt.% relative to the deposited layer weight.
16. The additively manufactured or refurbished HSLA component as claimed in claim 15, wherein the additively manufactured, refurbished, or wear-resistant region comprises tungsten carbide and ditungsten carbide phases distributed in an iron-based matrix and exhibits increased hardness and wear resistance relative to a corresponding HSLA region without tungsten carbide incorporation.
17. The additively manufactured or refurbished HSLA component as claimed in claim 15 or claim 16, wherein the additively manufactured, refurbished, or wear-resistant region comprises about 5 wt.% to 15 wt.% tungsten carbide relative to the deposited layer weight and exhibits a Vickers microhardness in a range of about 558.5 HV0.5 to 826.2 HV0.5.