Claims:WE CLAIM:
1. An optimized process (100) for additive manufacturing a component (202), the optimized process (100) comprising steps of:
providing a powder bed of low carbon ultra-high strength (LCUHS) steel powder on a substrate plate;
scanning the LCUHS steel powder with a laser to form a first layer of the component (202);
replenishing the powder bed and scanning the LCUHS steel powder with the laser to form a next subsequent layer of the component (202) onto the first layer; and
repeating the replenishing step to form the component (202),
wherein, a power associated with the laser is about 100-500W, a scan speed associated with the laser is about 0.85-1.00 m/s, and a thickness of the first layer and the subsequent layers is about 40-50 microns.
2. The optimized process (100) as claimed in claim 1, wherein the additive manufacturing technique used for the optimized process (100) includes a direct metal laser sintering technology.
3. The optimized process (100) as claimed in claim 1, wherein the laser is an Ytterbium doped fibre laser.
4. The optimized process (100) as claimed in claim 1, wherein a scan spacing is approx. 1.5 times the thickness of the first layer and the subsequent layers being formed.
5. The optimized process (100) as claimed in claim 1, wherein a laser dwell time is less than 40 µs.
6. The optimized process (100) as claimed in claim 1, wherein a laser spot size is less than 0.1 mm.
7. The optimized process (100) as claimed in claim 1, wherein the optimized process (100) further includes a post heat treatment of the component (202).
8. The optimized process (100) as claimed in claim 7, wherein the component (202) is kept in a furnace and heated to 468 ± 10 degree C for a prolonged time of 6 hours.

, Description:AN OPTIMIZED PROCESS FOR ADDITIVE MANUFACTURING A COMPONENT
FIELD OF INVENTION
[001] The present invention relates to metal processing using an additive manufacturing process. Particularly, the present invention relates to optimization of parameters to build components using additive manufacturing processes.

BACKGROUND OF THE INVENTION

[002] Additive manufacturing is a technology that builds three dimensional objects by adding layer upon layer of material. Each layer is generally very thin and laid one over another to from a definite shape. In contrast to subtractive manufacturing, where material is removed to form a component, additive manufacturing processes add material to build the desired component.

[003] Components during their period of operation encounter high stresses at their point of contact and at the tooth root. A component generally experiences bending fatigue and contact fatigue caused by bending stress and contact stress respectively. Since fatigue life is directly dependent upon the presence of high stress regions and the distribution of these stresses, stress relieving features are provided to distribute these stresses and to reduce their effect. But in that case, a compromise with component rigidity must be made. Low carbon ultra-high strength steels have exceptional mechanical strength however additive manufacturing of such materials is difficult. For example, mechanical performance of the steel is dependent on its microstructure which tends to become brittle when manufactured using this process and therefore prone to cracking.

[004] One solution to avoid cracking is to optimize the laser sintering parameters to get a desirable microstructure consisting of relatively ductile phases. However, additive manufacturing causes anisotropy in the mechanical properties in the direction of the build. Such anisotropy is undesirable and must be minimized.

OBJECTIVE

[005] The prime objective of the present invention is to provide an optimized parameter set for additive manufacturing of a component with less cracks and better mechanical properties.

[006] Another object of the invention is to give suitable post processing treatment to the manufactured component to increase its functional properties by eliminating anisotropy in properties.

SUMMARY OF THE INVENTION

[007] The present disclosure relates to an optimized process (100) of additive manufacturing a component (202), the optimized process (100) comprising steps of providing a powder bed of low carbon ultra-high strength (LCUHS) steel powder on a substrate plate; scanning the LCUHS steel powder with a laser to form a first layer of the component (202); replenishing the powder bed and scanning the LCUHS steel powder with the laser to form a next subsequent layer of the component (202) onto the first layer; and repeating the replenishing step to form the component (202), wherein, a power associated with the laser is about 100-500W, a scan speed associated with the laser is about 0.85-1.00 m/s, and a thickness of the first layer and the subsequent layers is about 40-50 microns.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[008] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:
Fig 1: illustrates an optimized process for additive manufacturing of a component.
Fig 2: illustrates the component build by the optimized process of Fig. 1
Fig 3: Schematic of tensile specimens taken from wall of the component built using the optimized process
Fig 4: Graph showing mechanical properties of the component along each direction

[009] The figure(s) depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

[0010] The present invention, now be described more specifically with reference to the following specification.

[0011] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.

[0012] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.

[0013] Figure 1 illustrates an optimized process 100 for additive manufacturing of a component 202, shown in Figure 2, in accordance with an embodiment of the present disclosure. In an embodiment, the additive manufacturing technique used for the optimized process 100 includes a direct metal laser sintering technology. Alternatively, the additive manufacturing technique may be selected from other technologies like selective laser sintering, selective heat sintering, selective heat melting, or the like.

[0014] In an embodiment, the component 202 is a low carbon ultra-high strength steel component build using the optimized process 100, wherein parameters associated with the process 100 are optimized in such a way to avoid cracking of the component 202. In an example, the ultra-high strength steel may be selected to have relatively low carbon content. For example, certain ultra-high strength steels are commercially available in a low carbon variant. Alternatively, or additionally, the ultra-high strength steel composition may be selected to have a carbon content towards the lower range of the alloy specification. In an example, as shown in Figure 2, the component 202 build through the optimized process 100 is a spur gear. Alternatively, the component 202 may be of any desired shape or structure.

[0015] Referring back to Figure 1, at step 102 the optimized process 100 includes providing a powder bed of low carbon ultra-high strength steel (LCUHS) powder on a substrate. At step 104, the optimized process 100 includes scanning the powder with a laser to create a melt pool and there selectively fuse the powder into a desired shape, thereby forming a first layer of the component. At step 106, the optimized process 100 includes replenishing the powder bed and scanning the powder with the laser to form a subsequent layer of the component onto the first layer. At step 108, the optimized process 100 includes repeating the step 106 as required until the desired three-dimensional component 202 is formed. In an embodiment, the optimized process 100 narrated above may be carried out at close to atmospheric pressure conditions.

[0016] In an embodiment, scanning the powder with the laser at step 104 of the optimized process 100 mentioned above further includes selective scanning of a focused laser beam across the surface of the powder bed in a line-by-line manner. In an example, spacing between adjacent scan lines is no more than twice the layer thickness being formed. In an example, the laser employed with the optimized process 100 is an Ytterbium doped fibre laser. Further, the laser power should be low, preferably less than 500W to melt thinner widths and give a better surface finish to the final component 202. In an example, the power associated with the laser should preferably be not less than 100W.

[0017] In an embodiment, with continued reference to the step 104 of the optimized process 100, the scan spacing associated with the selective scanning of the powder bed is preferably arranged to provide substantial overlapping of adjacent scan lines. In an example, the scan spacing may be approximately 1.5 times the thickness of the layer being formed. For example, the layer thickness is no more than 0.05 mm (50 microns) and may preferably be no more than 0.04 mm (40 microns).

[0018] Further, the scan spacing may be arranged such that selective scanning of a focused point source of energy across the surface of the powder bed melts the areas of the powder to form a layer followed by at least two remelts of that layer by adjacent scans of the laser beam. In an example, it has been observed that the optimized process 100 is particularly effective if the scan speed is relatively slow, for example less than 1 m/s, though about 0.85 m/s appears particularly effective (in comparison to conventional scanning at 1 m/s). In an example, the laser dwell time associated with the optimized process 100 may be less than 40 µs. It has been observed during the process 100, that a full power scan produces a more nearly crack free component than a lower power scan. Further, a laser spot size associated with the process 100 may have a nominal size of no more than 0.1 mm, and may for example be approximately 0.08 mm.

[0019] In an embodiment, the optimized process 100 further includes an additional step of applying a post heat treatment to the final component 202. The results associated with the optimized process 100 shows that it is particularly advantageous to apply the post heat treatment prior to removal of the component 202 from any substrate (base plate) on which the component 202 has been formed. In an example, the component 202 is effectively welded to the substrate after additive layer manufacturing. This reduces the risk of the component 202 undergoing mechanical relaxation prior to post heat treatment.

[0020] In an example, the post heat treatment mentioned above may be done in a furnace, for example by heating the final component 202 at not more than 500 degree C. Preferably, the final component 202 should be heated to 468 ± 10 degree C for a prolonged time of 6 hours. Mostly, the component 202 is treated to remove anisotropy in properties in the direction of the build. As known in the art, Anisotropy in additively manufactured materials arise due to various factors like interlayer bonding, porosity, cooling rates and resultant microstructure. However, the component 202 produced through the above-mentioned process 100 with optimized parameters showed no porosity as seen in Figure 3. Also, the post heat treatment modified the resultant microstructure to deliver uniform properties both along the build direction and perpendicular to the build direction as shown in Figure 4.

[0021] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims.