Process for reinforcing wear resistance of Ti-DLC plasma injection bearing

Abstract

This invention relates to the field of bearing technology, specifically to a process for enhancing the wear resistance of bearings through Ti-DLC plasma implantation, comprising the following steps: A: After fine grinding and ultrasonic cleaning of the surface of the bearing component substrate, it is placed in a vacuum chamber, argon gas is introduced and the radio frequency power supply is started, while a pulsed voltage is applied to the substrate for plasma etching; B: Maintaining the argon atmosphere, magnetron sputtering of the Ti target is started, while a high-voltage pulse is applied to the substrate, causing the Ti... + Ion implantation forms a pure Ti transition layer on the substrate surface, followed by the gradual introduction of hydrocarbon gas to make the Ti... + Co-implantation deposition with carbon ions forms a Ti-TiC transition layer; C: maintain Ti target sputtering, adjust the flow ratio of argon gas to hydrocarbon gas, reduce the substrate pulse voltage, control the deposition temperature ≤200℃, and deposit to form a Ti-doped diamond-like carbon (Ti-DLC) core layer. The purpose of this invention is to solve the problem of easy peeling of coatings in the prior art.

Description

Technical Field

[0001] This invention relates to the field of bearing technology, specifically to a process for enhancing the wear resistance of bearings through Ti-DLC plasma implantation. Background Technology

[0002] As a core component of the machinery industry, bearings directly affect the lifespan and reliability of equipment due to the surface properties of their raceways and rolling elements. GCr15 bearing steel, Si3N4 ceramics, and 304 stainless steel are typical base materials for bearing manufacturing, but in practical applications, they all face problems such as surface wear, fatigue spalling, and lubrication failure to varying degrees.

[0003] Diamond-like carbon (DLC) coatings are widely used for bearing surface modification due to their high hardness, low coefficient of friction, and good chemical inertness. However, when DLC coatings are applied to bearing components, the coating is prone to peeling. There are significant differences in physical and chemical properties (such as hardness, coefficient of thermal expansion, lattice constant, etc.) between the DLC coating and the metal or ceramic substrate, resulting in insufficient interfacial adhesion and easy peeling failure under cyclic contact stress. To solve this problem, existing technologies often use the method of constructing a gradient transition layer, such as introducing a pure metal layer (such as Cr, Ti, W) or a metal carbide layer between the substrate and the DLC coating. However, multi-level fine gradient design often requires complex process control and precise atomic percentage control, resulting in poor stability in industrial mass production and high equipment modification costs. Summary of the Invention

[0004] The purpose of this invention is to provide a process for strengthening the wear resistance of bearings by Ti-DLC plasma implantation, so as to solve the problem of easy peeling of coatings in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A process for enhancing the wear resistance of bearings through Ti-DLC plasma implantation includes the following steps:

[0007] A: After fine grinding and ultrasonic cleaning of the bearing component substrate surface, it is placed in a vacuum chamber, argon gas is introduced and the radio frequency power supply is turned on. At the same time, a pulse voltage is applied to the substrate to perform plasma etching.

[0008] B: Maintain an argon atmosphere, initiate magnetron sputtering of the Ti target, and simultaneously apply a high-voltage pulse to the substrate, causing the Ti... + Ion implantation forms a pure Ti transition layer on the substrate surface, followed by the gradual introduction of hydrocarbon gas to allow Ti⁺ and carbon ions to be co-implanted and deposited, forming a Ti-TiC transition layer;

[0009] C: Maintain Ti target sputtering, adjust the flow ratio of argon to hydrocarbon gas, reduce the substrate pulse voltage, control the deposition temperature ≤200℃, and deposit to form a Ti-doped diamond-like carbon (Ti-DLC) core layer;

[0010] D: Turn off the Ti target and hydrocarbon gas, heat the cavity to 220~260℃ in a vacuum environment and hold it at that temperature, then let it cool naturally to room temperature.

[0011] Preferably, the parameters for plasma etching in step A are: argon flow rate 20~35 sccm, RF power supply power 300~450W, substrate pulse voltage -12~-20kV, and processing time 12~18min.

[0012] Preferably, the parameters for forming the pure Ti transition layer in step B are: Ti target power 700~1000W, substrate high voltage pulse voltage -25~-40kV, and pure Ti transition layer thickness 0.2~0.4μm.

[0013] Preferably, the parameters for forming the Ti-TiC transition layer in step B are: gradually increasing the hydrocarbon gas flow rate from 5-8 sccm to 18-30 sccm within 3-5 minutes to form a Ti-TiC transition layer with a thickness of 0.3-0.6 μm.

[0014] Preferably, the parameters for depositing the Ti-DLC core layer in step C are: Ti target power 700~900W, argon to hydrocarbon gas flow ratio 1:1~1:1.5, total flow rate 40~60sccm, substrate pulse voltage -8~-15kV, pulse frequency 40~80Hz, deposition time 45~75min, Ti-DLC core layer thickness 1.2~2.0μm, and Ti doping atomic percentage 3~8at.%.

[0015] Preferably, the heat preservation time in step D is 25~30 minutes.

[0016] Preferably, the hydrocarbon gas is acetylene.

[0017] Preferably, the bearing component substrate is any one of GCr15 bearing steel, Si3N4 ceramic bearing, or 304 stainless steel bearing.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. Through a simplified design of "Ti transition layer implantation + Ti-TiC transition layer", high-voltage pulses are used to realize Ti... +Ion implantation forms a hybrid interface on the substrate surface, and then the gradual introduction of hydrocarbon gas naturally forms a Ti content gradient transition, achieving an effective connection between "substrate-Ti-TiC-DLC". This design abandons the traditional complex multi-layer gradient structure, has strong industrial feasibility, and significantly improves coating adhesion, fundamentally solving the peeling problem. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] All embodiments of this invention employ the same industrial-grade plasma implantation deposition system, the configuration of which includes: ultimate vacuum degree ≤ 1×10⁻⁶. -3 A vacuum chamber with a purity of ≥99.9%; a single magnetron sputtering Ti target; a carbon source gas path equipped with a radio frequency (RF) power supply (using conventional hydrocarbon gases such as acetylene or methane); a high-voltage pulse power supply adjustable from 0-60kV; and a substrate temperature control system capable of achieving precise temperature control from room temperature to 250°C; all embodiments use GCr15 bearing steel, Si3N4 ceramic, or 304 stainless steel bearing components as substrates.

[0022] Example 1 (GCr15 bearing steel):

[0023] Step A: Substrate Pretreatment: GCr15 bearing steel raceway or rolling element surface is finely ground to a surface roughness Ra≤0.03μm, then placed in acetone and anhydrous ethanol sequentially, and ultrasonically cleaned for 12min each time to remove surface oil and impurities. The cleaned component is then placed into a vacuum chamber and evacuated to 1×10⁻⁶. -3 At Pa, argon gas (Ar) is introduced at a flow rate controlled at 28 sccm. The radio frequency power supply is started and set to 380W. Simultaneously, a -15kV pulse voltage is applied to the substrate, utilizing Ar... + Ions were used to perform plasma etching on the surface for 15 minutes to remove the oxide layer and form a micro-roughened surface.

[0024] Step B: Preparation of the Ti-TiC transition layer: Maintaining the Ar gas flow rate at 28 sccm, start magnetron sputtering of the Ti target at a power of 850 W to produce Ti. + Plasma, while simultaneously applying a -32kV high-voltage pulse to the substrate, causes Ti to... +Ion implantation was performed on the substrate surface to form a pure Ti transition layer with a thickness of approximately 0.3 μm. Subsequently, while maintaining Ti target sputtering and a high-voltage pulse on the substrate, the acetylene (C2H2) flow rate was uniformly increased from 6 sccm to 22 sccm over 5 minutes. During this process, Ti... + Co-implantation deposition with carbon ions forms a Ti-TiC transition layer with a thickness of approximately 0.45 μm.

[0025] Step C: Ti-DLC core layer deposition: Maintain Ti target power at 800W, adjust the process gas ratio to make the flow ratio of Ar gas to acetylene 1:1.2 (total flow rate 50sccm), reduce the substrate pulse voltage to -12kV, set the pulse frequency to 60Hz, control the substrate temperature during deposition to not exceed 200℃ (actually measured to be 195℃), and the deposition time is 60min, forming a Ti-DLC core layer with a thickness of 1.8μm. Through the coordinated control of Ti target power and gas ratio, the percentage of Ti doped atoms in the coating is approximately 5.5 at.%.

[0026] Step D: Low-temperature stress-relief annealing: Turn off the Ti target power supply and hydrocarbon gas source, maintain a vacuum environment, start the substrate temperature control system, raise the chamber temperature to 240°C, hold for 28 minutes, stop heating after holding, allow the chamber to cool naturally to room temperature under vacuum conditions, finally raise the chamber pressure back to atmospheric pressure, and remove the coated bearing component.

[0027] Example 2 (Si3N4 ceramic bearing):

[0028] This embodiment is basically the same as Embodiment 1, except that some parameters were adjusted as follows to take into account the chemical inertness and surface characteristics of the ceramic substrate: the pulse voltage of plasma etching in step A was increased to -19kV; the final upper limit of acetylene flow rate in step B was increased to 30sccm; the deposition time in step C was adjusted to 50min, and a total coating thickness of about 1.4μm was obtained; all other parameters and operations are the same as in Embodiment 1.

[0029] Example 3 (304 stainless steel bearing):

[0030] This embodiment is basically the same as Embodiment 1, except that some parameters were adjusted as follows to take into account the characteristics of the thick oxide layer and high coefficient of thermal expansion of austenitic stainless steel: the plasma etching time in step A was extended to 18 min; the annealing temperature in step D was set to 230℃; the deposition time in step C was adjusted to 55 min, and a total coating thickness of about 1.6 μm was obtained; all other parameters and operations are the same as in Embodiment 1.

[0031] To highlight the synergistic effect of each key step in the technical solution of the present invention and the technical effect achieved, the following comparative examples are set. All comparative examples use GCr15 bearing steel as the base material, and except for the specially specified changed parameters, the other steps and process parameters are exactly the same as those in Example 1.

[0032] Comparative Example 1 (Ti-TiC transition layer omitted):

[0033] Step B is cancelled. After the plasma etching in step A is completed, the Ti-DLC core layer deposition in step C is performed directly (parameters are the same as in Example 1). The rest is the same as in Example 1.

[0034] Comparative Example 2 (high-pressure pulse injection omitted, pure deposition mode used):

[0035] In steps B and C, no high-voltage pulse is applied to the substrate (i.e., the substrate voltage is always 0V), and thin film deposition is performed solely by magnetron sputtering and RF discharge, with the rest being the same as in Example 1.

[0036] Comparative Example 3 (low-temperature stress-relief annealing omitted):

[0037] After completing the Ti-DLC core layer deposition in step C, all power and gas are turned off directly, and the vacuum chamber is allowed to cool naturally to room temperature. The heating and holding annealing process in step D is not performed. The rest is the same as in Example 1.

[0038] The coating samples prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests. Five parallel samples were taken for each sample, and the test results were taken as the arithmetic mean.

[0039] Coating adhesion: The scratch method was used with a Rockwell C diamond indenter at a loading rate of 100 N / min and a scratch length of 3 mm. The normal load (denoted as Lc2, in N) corresponding to the first consecutive peak value of the acoustic emission signal was recorded. The higher the Lc2 value, the stronger the adhesion between the coating and the substrate.

[0040] Coating hardness: The coating hardness (in GPa) was calculated using a nanoindenter with a Berkovich diamond indenter, a maximum load of 10 mN, and a holding time of 10 s, and by the Oliver-Pharr method.

[0041] Friction and wear performance: A ball-and-disc friction and wear tester was used to test the wear pair of Φ6mm GCr15 steel balls. The load was 5N, the rotation speed was 500r / min, the rotation radius was 5mm, and the test time was 30min. The average friction coefficient was recorded throughout the process, and the peeling of the coating surface was observed after the test.

[0042] Impact spalling resistance: In accordance with VDI 3198 standard, a Rockwell hardness tester was used to apply a load of 1471 N (HRC) to form an indentation on the coating surface. The morphology around the indentation was observed using a 200x optical microscope. The HF grade was evaluated based on the spalling and cracking conditions (HF1 is the best, and HF6 is the worst).

[0043] All test results are summarized in the table below.

[0044] Example 1 48.2 22.5 0.12 No peeling HF1 Example 2 43.5 21.8 0.13 No peeling HF1~HF2 Example 3 39.1 20.9 0.14 No peeling HF2 Comparative Example 1 17.3 23.1 0.16 Large-area peeling (around 8 minutes) HF5 Comparative Example 2 28.6 19.5 0.18 Localized, pinpoint peeling (around 22 minutes) HF4 Comparative Example 3 32.4 22.8 0.15 Microcrack propagation, edge peeling HF3

[0045] Results analysis:

[0046] As can be seen from the test results of Examples 1-3, the core process of "substrate cleaning and activation → Ti transition layer injection → Ti-DLC core layer deposition → low-temperature stress-relief annealing" provided by this invention has successfully prepared Ti-DLC coatings with excellent comprehensive performance on three typical substrates: GCr15 bearing steel, Si3N4 ceramic bearings, and 304 stainless steel bearings. Among them, Example 1 (GCr15) has an adhesion strength as high as 48.2N and a friction coefficient as low as 0.12, showing good adhesion and wear resistance. Examples 2 and 3 also show good adhesion and wear resistance, proving that this invention has good universal adaptability to different substrates.

[0047] A comparison of Comparative Example 1 and Example 1 shows that, after omitting the Ti-TiC transition layer, the coating adhesion dropped sharply to 17.3 N, and large-area peeling occurred in about 8 minutes during the friction and wear test. This indicates that the transition layer described in this invention is the core technical feature for solving the coating peeling problem.

[0048] A comparison of Comparative Example 2 and Example 1 shows that when no high-pressure pulse is applied (i.e., pure deposition mode), the coating adhesion is significantly reduced and local peeling occurs, proving that the interface hybrid layer formed by high-pressure pulse-assisted injection has an irreplaceable role in improving coating adhesion.

[0049] A comparison of Comparative Example 3 and Example 1 shows that, after omitting the low-temperature stress-relief annealing, the coating's adhesion and impact resistance (HF3) are inferior to those of Example 1 (HF1), and microcrack propagation and edge spalling occur. This proves that low-temperature annealing at 220~260℃ can effectively release the internal stress of the coating and significantly improve the coating's fatigue life and spalling resistance.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for enhancing the wear resistance of bearings through Ti-DLC plasma implantation, characterized in that, Includes the following steps: A: After fine grinding and ultrasonic cleaning of the bearing component substrate surface, it is placed in a vacuum chamber, argon gas is introduced and the radio frequency power supply is turned on. At the same time, a pulse voltage is applied to the substrate to perform plasma etching. B: Maintain an argon atmosphere, initiate magnetron sputtering of the Ti target, and simultaneously apply a high-voltage pulse to the substrate, causing the Ti... + Ion implantation forms a pure Ti transition layer on the substrate surface, followed by the gradual introduction of hydrocarbon gas to make the Ti... + Co-implantation deposition with carbon ions forms a Ti-TiC transition layer; C: Maintain Ti target sputtering, adjust the flow ratio of argon to hydrocarbon gas, reduce the substrate pulse voltage, control the deposition temperature ≤200℃, and deposit to form a Ti-doped diamond-like carbon (Ti-DLC) core layer; D: Turn off the Ti target and hydrocarbon gas, heat the cavity to 220~260℃ in a vacuum environment and hold it at that temperature, then let it cool naturally to room temperature.

2. The process for enhancing the wear resistance of bearings by Ti-DLC plasma implantation according to claim 1, characterized in that, The parameters for plasma etching in step A are: argon flow rate 20~35 sccm, RF power supply 300~450W, substrate pulse voltage -12~-20kV, and processing time 12~18min.

3. The process for enhancing the wear resistance of bearings by Ti-DLC plasma implantation according to claim 1, characterized in that, The parameters for forming the pure Ti transition layer in step B are: Ti target power 700~1000W, substrate high voltage pulse voltage -25~-40kV, and pure Ti transition layer thickness 0.2~0.4μm.

4. The process for enhancing the wear resistance of bearings by Ti-DLC plasma implantation according to claim 1, characterized in that, The parameters for forming the Ti-TiC transition layer in step B are as follows: the flow rate of hydrocarbon gas is gradually increased from 5-8 sccm to 18-30 sccm within 3-5 min to form a Ti-TiC transition layer with a thickness of 0.3-0.6 μm.

5. The process for enhancing the wear resistance of bearings by Ti-DLC plasma implantation according to claim 1, characterized in that, The parameters for depositing the Ti-DLC core layer in step C are as follows: Ti target power 700~900W, argon to hydrocarbon gas flow ratio 1:1~1:1.5, total flow rate 40~60sccm, substrate pulse voltage -8~-15kV, pulse frequency 40~80Hz, deposition time 45~75min, Ti-DLC core layer thickness 1.2~2.0μm, and Ti doping atomic percentage 3~8at.%.

6. The process for enhancing the wear resistance of bearings by Ti-DLC plasma implantation according to claim 1, characterized in that, The heat preservation time in step D is 25~30 minutes.

7. The process for enhancing the wear resistance of bearings by Ti-DLC plasma implantation according to claim 1, characterized in that, The hydrocarbon gas is acetylene.

8. The process for enhancing the wear resistance of bearings by Ti-DLC plasma implantation according to claim 1, characterized in that, The bearing component base material is any one of GCr15 bearing steel, Si3N4 ceramic bearing, or 304 stainless steel bearing.