The present disclosure relates to a process for surface treatment of steel components. BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Steel components such as roller bearings used in automobile applications are subjected to wear due to continuous surface fatigue mechanism, which can cause failure of the roller bearings. Gear oils are formulated to enhance gear performance especially in gearbox and transmissions. In those positions, bearings are also installed and are lubricated with the same gear oils. It is observed that sliding is greater in gear mechanism than in rolling bearings (slide/roll ratio) and gear oils are formulated accordning to this condition. During the operation of roller bearings, a thin film / layer is formed due to the additive's reaction with metals parts as adsorption / absorbance mechanism present in the lubricant used. It is often seen that the layer formed exerts traction forces near the surface, which changes shear stress and induce microstructure changes in the tribological performance (friction and wear) followed by the initiation of surface micro-cracking, which results in failure.
In addition, due to the nature of contact geometryof roller bearings, the sliding mechanism is high between rolling elements and inner rings. Due to high sliding conditions, traction forces push the maximum shear stress location near the surface and the roller bearings are prone to fail due to adhesion wear, which can further accelerate the other failure modes such as surface-initiated spalling and seizure.
There is, therefore, felt a need to develop a process for prevention of steel components failure for better performance.

OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for increasing wear resistance of steel components.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
In one aspect, the present disclosure provides a process for increasing wear resistance of steel components. The process comprises the following steps.
The surface of steel components can be oxidized by contacting the steel components with an alkali for a predetermined time period and at a first predetermined temperature. Further, the components can be cold rinsed followed by hot rinsing at a second predetermined temperature to obtain rinsed components; and drying the rinsed components in an inert atmosphere to obtain components having increased wear resistance.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The embodiments of the present disclosure will now be described with the help of the accompanying drawing, in which:

Figures 1 illustrates averaged coefficient of friction value of different components under different process conditions;
Figures 2A and 2B Comparative illustration of averaged coefficient of friction and averaged wear between oxide treated and conventional treated components;
Figure 3 illustrates schematic diagram of variable sliding to rolling test;
Figure 4 illustrates averaged wear and averaged friction response of different samples;
Figure 5 illustrates friction response with respect to time of three different combinations;
Figure 6 represents endurance test comparison of oxide treated bearings and untreated bearings
Figure 7 illustrates low lambda test result data of the oxide treated bearings and conventional bearing;
Figure 8 represents raceaway topography of inner ring of conventional bearing and oxide treated bearing after testing; and
Figure 9A and 9B illustrates Electron Disperse Spectroscope (EDS) spectrum on the inner ring raceway before and after endurance tested oxide layer treated bearings.
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details, are set forth, relating to specific components, and methods, to provide a complete understanding of

embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a," "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," "including," and "having," are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
When an element is referred to as being "mounted on," "engaged to," "connected to," or "coupled to" another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

Terms such as “inner,” “outer,” "beneath," "below," "lower," "above," "upper," and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.
In one aspect, the present disclosure provides a process for increasing wear resistance 5 of steel components. The process comprises steps of controlled oxidizing of the surface of the steel components by contacting the components with an alkali for a predetermined time period and at a first predetermined temperature; cold rinsing the components followed by hot rinsing at a second predetermined temperature to obtain rinsed components; and drying the rinsed components to obtain components having 10 increased wear resistance.
The steel components before the oxidizing step can be degassed and/ or derusted. Further, the steel components can be contacted with an alkali for a predetermined temperature and at a predetermined time.
In accordance with the embodiments of the present disclosure, the alkali can be a 15 metal compound selected from the group consisting of sodium nitrate, sodium nitrite, sodium hydroxide and/ or from the group consisting of potassium hydroxide, potassium nitrate and potassium nitrite and combinations thereof.
Typically, the first predetermined temperature in the range of 110°C to 150°C. The steel components can be contacted with the alkali for a predetermined time in the 20 range of 20-60 minutes.
Further, the step of cold rinsing is performed that involves quenching followed by hot rinsing at a second predetermined temperature. In accordance with the present disclosure, the second predetermined temperature can be in a range of 70°C to 90°C.
Preferably, the oxidizing and rinsing steps can be reiterated by sequentially increasing 25 the temperature during each iteration and in each iteration, the concentration of the
6

alkali is kept constant. In accordance with the present disclosure, the temperature of the alkali is increased by 5°C sequentially in each iteration.
Further, the drying step is carried out at an inert atmosphere to obtain components with improved wear resistance.
5 In a second aspect, the present disclosure provides a steel component comprising a layer of oxide on its surface, having thickness in the range of 2 micron to 4 micron.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to 10 industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
The following tribological experiments were conducted using roller bearings obtained after surface treatment in accordance with the present disclosure in comparison with the conventional roller bearings.
15 Tribology is a science of wear, friction and lubrication and encompasses how interacting surfaces and other triboelements behave in relative motion.
Experiment:
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual 20 components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
Experiment 1: Preparation of surface treated steel roller bearings
7

Roller bearings were degassed by washing with preferably isopropyl alcohol. The
degassed bearings were contacted with an alkali to oxidize the surface of the steel
roller bearings. The temperature of the alkali was maintained at 110°C. The roller
bearings were then cold rinsed followed by hot rinsing at a temperature of 80°C. The
5 process steps of contacting the roller bearings with the alkali, cold rinsing and hot
rinsing was sequentially repeated 4 times, wherein the temperature of the alkali was
maintained at 125°C, 135°C and 150°C respectively and the concentrations of the
alkali was 65 wt% sodium hydroxide, 25wt% sodium nitrite and 10 wt% sodium
nitrate. After 4 successive steps of contacting with the alkali, cold rinsing and hot
10 rinsing, the roller bearings were vacuum dried followed by applying oil to obtain the
roller bearings having an oxide layer.
Experiment 2: Testing of surface treated roller bearings.
Several tests were carried out on the surface treated roller bearings to check the wear
resistance. The oxide layer was prepared with three different process times which
15 were marked as trial 1,2 and 3 for 30, 40 and 50 minutes respectively.
Experiment 2A: Ball on disc wear test.
Tribological performance was compared with two different types of test as per the
combination mentioned in table 1. The samples were run to tribometer ball on disc
test for 5 km. Coefficient of friction (COF) and Z position of the slider was monitored
20 and stored for post test analysis.
Table 1: Ball on disc testing parameters

Parameter Description
Module Ball-on-disk
Ball JIS SUJ2, 6.35 mm diameter
8

Disc JIS SUJ2, 69.85 mm diameter
Sliding distance 5000 m
Linear velocity 0.5 m/s
Load 2.5 GPa
Lubricant 5ml ISO VG32 oil
Atmosphere Air, relative humidity 40~50%. Temperature 25°C
Results are plotted in Figure 1
Combinations Trial 1 Trial 2 Trial 3
Processing time period (mins) 30 40 50
Ball Oxide treated Oxide treated Oxide treated
Discs No oxide layer No oxide layer No oxide layer
Results are plotted in Figure 2 A & 2B
Combinations A C
Ball Oxide treated (as per Trial 2 process) No oxide layer
Discs Oxide treated (as per Trial 2 process) No oxide layer
Wear measurement was obtained based on the Z position of sensor movement which indicates the total wear of ball and disc. The influence of oxide layer on tribological parameter was analyzed. It was observed that the performance of the layer was
9

dependent on immersion time. When the parts were immersed 50 minutes (Trial
number 3), the chemical reaction exerted porosity and chemical erosion on the steel
parts, which deteriorated the surface topography and performance. When immersed
for 30minutes (Trial number 01), a thin layer was formed which reduced the
5 performance of the parts. The oxide layer (Fe3O4) being soft in nature, readily sheared
in the contact, and reduced the friction between the surface. Figure 1 indicates that the Trail 2 has yielded lowest COF.
Figure 2A & 2B shows the coefficient of friction and wear with respect to
conventional bearings (A) and oxide treated combination (C) respectively. From the
10 figures, it can be seen that the oxide layer reduced the friction around 70% than the
conventional steel to steel contact at 0.5m/s sliding speed. As adhesion was restricted due to introduction of the oxide layer, the dissimilar material could not produce adhesion mechanism, thereby reducing the wear to 77% at the particular sliding speed.
15 Experiment 3: Variable Rolling to sliding wear test
The test conditions were as per table 2. Rollers were loaded between two discs and rollers were held by specially made retainer as shown in figure 2. Three rollers (R) (5 x 16 mm diameter) were evenly spaced such a way run at 65% rolling to sliding speed with two discs namely upper disc (D1) and lower disc (D2). The rollers and
20 rings were prepared of bearing steel as per the present process (Trial 2) and a second
batch was prepared using the conventional method without oxide layers (A). The surface roughness of discs were kept higher to run at the mixed lubrication conditions and rollers were super finished. The lubrication conditions during the tests were maintained in mixed lubrication by using thin gear oil while applying the contact
25 pressure . Tests were conducted under identical condition for conventional and after
the tests, results were compared.
10

Table 2: Testing condition

Parameter Description
Module Rolling to sliding 65%
Roller JIS SUJ2, ϕ 5 x 16 mm length
Discs JIS SUJ2, 67.0 mm diameter
Contact cycle 1.35 Lacs
Linear velocity 0.5 m/s
Contact pressure 0.3 GPa
Lubricant ISO VG32 oil
Atmosphere Air, relative humidity 40~50%, Temperature 25°C
Combinations Set 1(A) Set 2 (B) Set 3 (C)
Rollers No oxide layer No oxide layer Oxide layer
Discs No oxide layer Oxide layer Oxide layer
It was observed that set 3 (C) showed improved performance in terms of coefficient
of friction (X) and wear (Y) as compared to set 1 (A) and set 2 (B) as depicted in
5 figure 3. The oxide layer extends the range of surface safe operating conditions as
compared to the conventional bearing steel surfaces.
The oxide layer adds beneficial properties to the bearing operation such as improved running in phase thereby resulting in improved surface properties after running-in and
11

better performance under poor lubrication condition (low kappa conditions) with improved lubricant adhesion.
It was observed from the test that both discs and rollers, when treated with the oxide
layer provided higher attribution than the conventional discs and rollers without the
5 oxide layer. Fe3O4 oxide films provides less friction and wear reduction in the
boundary lubrication region due to chemical dissimilarity. Friction reduction and
adhesive wear protection relative to untreated steel contacts were also observed.
Based upon the experimental results, the use of oxide treated discs in contact with
oxide treated rollers (C) showed improved performance rather than oxide treated
10 discs in contact with untreated roller (B) and steel to steel with no oxide layer (A) as
shown in figure 4.
Experiment 4: Bearing Endurance Test (Figure 6)
Two types of bearing endurance life testing were conducted. In both types, deep
groove ball bearing 6207 were used. The first test group of bearings were prepared
15 according to the present method (Inner ring, outer ring and rolling element all treated)
and a second group as per the conventional process. Test conditions are furnished in table 3. The test lubricant was ISO VG 68 Mineral oil.
Table 3: Bearing life test parameters

Description Values
Type of test 1st in 2
Part number DGBB 6207
Bearing size (OD & Bore dia. in mm) 72 x 35
Radial Load (kN) 6.45
Rotational Speed (rpm) 3000
12

Temperature (°C) 60
Lubrication method Oil jet
Lubricant ISO VG68
Kinematic viscosity at 40°C (mm2s-1) 68
Density at 15°C (kgm-3) 865
The bearing endurance test indicated similar trend indicated by tribometer wear test
where the oxide layers bearings set 3 (A) provide better performance than the
conventional steel to steel pair 6207 (A) as seen in figure 6. In the test, all oxidized
5 bearings were tested in well defined value without any failures, resulting in a life
estimate that was 4.4 times above the life of the conventional bearings.
Experiment 5: Oil starvation test
The test was conducted with reduced oil flow quantity to exert oil starvation, which
produces complex stresses for test conditions which are furnished in table 4 as per the
10 combinations. The bearings B & C was prepared as per the present process and a
bearing A was prepared as per the conventional process. The test lubricant was ISO VG 10 Mineral oil.
Table 4: Bearing life test parameters

Description Values
Type of test 1st in 2
Part number DGBB 6207
Bearing size (OD & Bore dia. in mm) 72 x 35
Radial Load (kN) 6.45
13

Lubrication method Oil jet
Lubricant ISO VG10
Kinematic viscosity at 40°C (mm2s-1) 10
Density at 15°C (kgm-3) 850
Kappa value (k) 0.5
Lambda (λ) 1.5
Better results were observed with oxidized bearings (C & B) of the present process as compared with the conventional bearings (A) with respect to low kappa lubrication conditions as seen in figure 7.
5 The deterioration of surface due to metal to metal contact under boundary / mixed
lubrication can be seen in table 5. The oxide layer bearings showed good surface roughness even while operating for prolonged period of time as compared to the conventional bearings.
Table 5: Average surface roughness on the raceways

Description Fresh inner ring Oxide layered after tests Conventional after tests
3D average surface roughness 0.07 micron 0.11 micron 0.18 micron
10
The Figure 8 indicates the raceway surface topography of fresh and tested bearings of A & C. small black dot marks indicate surface damage in the figure. The C group have many such a marks when compared to A
14

Electron Disperse Spectroscope (EDS) analysis as shown in figures 9A and 9B, The arrow marks indicate that location of X-ray spectrum collected. The figure showed oxygen contents in the raceway surface of inner ring in the range of 10.9% and 4.89%, before and after the tests, respectively. The analysis showed that a 5 considerable amount of oxide layer still remained in the contact zone after the test, i.e. only partial layer was removed. The oxide layer acted like a sacrificial layer, thereby showing improvement during running-in, and enhanced tribological performance (e.g. lower boundary lubrication friction and risk of micropitting).
The surface treated roller bearings having an oxide layer on its surface, in accordance 10 with the present disclosure, shows improved wear resistance.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
- steel components with increased wear resistance.
15 The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the
20 embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general
nature of the embodiments herein that others can, by applying current knowledge,
25 readily modify and/or adapt for various applications such specific embodiments
15

without departing from the generic concept, and, therefore, such adaptations and
modifications should and are intended to be comprehended within the meaning and
range of equivalents of the disclosed embodiments. It is to be understood that the
phraseology or terminology employed herein is for the purpose of description and not
5 of limitation. Therefore, while the embodiments herein have been described in terms
of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more
10 elements or ingredients or quantities, as the use may be in the embodiment of the
disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has
been included in this specification is solely for the purpose of providing a context for
the disclosure. It is not to be taken as an admission that any or all of these matters
15 form a part of the prior art base or were common general knowledge in the field
relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or
quantities are only approximations and it is envisaged that the values higher/lower
20 than the numerical values assigned to the parameters, dimensions or quantities fall
within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and
component parts of the preferred embodiments, it will be appreciated that many
25 embodiments can be made and that many changes can be made in the preferred
embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure
16

will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation

WE CLAIM:

A process for increasing wear resistance of steel components, said process comprising:
controlled oxidization of the surface of said components with an alkali for a predetermined time period and at a first predetermined temperature;
cold rinsing said components followed by hot rinsing at a second predetermined temperature to obtain rinsed components; and
drying said rinsed components in an inert atmosphere to obtain components with increased wear resistance.
The process as claimed in claim 1, wherein prior to step (a) of oxidizing, said components are degreased and/or derusted.
The process as claimed in claim 1, wherein said first predetermined temperature is in the range of 100°C to 150°C and said predetermined time is in the range of 5-15 minutes.
The process as claimed in claim 1, wherein said at least one alkali is a metal selected from the group consisting of sodium nitrate, sodium nitrite, sodium hydroxide and from a group consisting of potassium hydroxide, potassium nitrate and potassium nitrite and combinations thereof.
The process as claimed in claim 1, wherein said step of cold rinsing comprises quenching.
The process as claimed in claim 1, wherein said second predetermined temperature is in the range of 70°C to 90°C.

The process as claimed in claim 1, wherein said oxidizing and said rinsing steps are reiterated by sequentially increasing the temperature during each iteration and in each iteration.
The process as claimed in claim 7, wherein the temperature of the alkali is increased by 5°C sequentially in each iteration.
The process as claimed in claim 1, wherein said step of drying is carried out by hot gas drying, or vacuum drying.
L A steel component comprising a layer of oxide on its surface having thickness in the range of 2 micron to 4 micron; said component with oxidized surface being characterized by improved wear resistance.
. The process as claimed in claim 1, wherein said steel component is a roller bearing.