CN116162981A - DLC film friction induced graphitization phase change inhibition method - Google Patents

Abstract

The invention discloses a DLC thin film friction-induced graphitization phase change suppression method, which relates to the technical field of mechanical design friction and lubrication. The main points of the technical scheme are: firstly, adding palladium nanoparticles into alkane base oil and ultrasonically dispersing to obtain palladium-containing nanoparticles As a DLC film friction-induced graphitization inhibitor additive; then the lubricant is used in the friction and wear experiment of DLC film and bearing steel. In the present invention, palladium nanoparticles are used as tribochemical catalysts, and the complex friction environment is used to drive the palladium nanoparticle catalysts to catalytic dehydrogenation of alkane base oils, forming amorphous carbon-based friction films in situ, and realizing the suppression of DLC films caused by friction. Graphitization phase transition, thereby reducing the degradation of tribological properties of DLC films caused by graphitization.

Description

A method for suppressing phase transition of DLC film friction-induced graphitization

technical field

The invention relates to the technical field of mechanical design friction and lubrication, more specifically, it relates to a method for suppressing phase transition of DLC film friction-induced graphitization.

Background technique

Diamond-like carbon film (DLC) is a kind of carbon film mainly hybridized with sp2-C and sp3-C, because it has the properties of diamond and graphite at the same time, that is, it has good wear resistance and self-lubrication, so it is often used Used in the field of tribology. However, due to the action of frictional temperature rise and shear, the DLC film will undergo a graphitization phase transition to reduce its wear resistance, and this phase transition is irreversible and cannot be automatically compensated, thus reducing the service life of the DLC film.

Among the technologies related to coping with the graphitization of DLC films, a vanadium/yttrium co-doped DLC coating and its preparation method (CN113913735A) discloses that the doping of yttrium can increase the temperature at which graphitization of DLC films occurs, that is, it increases the temperature of DLC films. Thermal stability, thereby reducing the process of DLC film graphitization. A treatment method for slowing down DLC film graphitization (CN104498911A) discloses a method for slowing down DLC film graphitization in a laser system by depositing an electrode on the surface of a DLC film: when a bias voltage is applied to the electrode by a DC power supply, the generated transverse or vertical electric field can effectively Reduce the thermal energy generated in the laser irradiation area, thereby slowing down the graphitization of the film. Among the above technologies, the former is to change the composition or microstructure of the DLC film through element co-doping in the DLC preparation process, which increases the graphitization temperature of the DLC film; the latter is to apply a bias voltage during the application process to make the laser irradiate the area The energy is reduced, thereby slowing down the graphitization of the film. The degradation of the tribological properties of the DLC film due to the graphitization phase transition caused by frictional slip shear motion and frictional heat cannot be avoided in the prior art.

In addition, a tribocatalytic design method for realizing ultra-low friction of carbon films (CN112210417A) utilizes the catalytic synergistic effect to make use of the adsorption passivation and phase transition of active metal nanoparticles on carbon, so that the amorphous carbon structure of carbon films can be transformed into graphene. Ordered transformation, forming a ball-like anti-friction product of graphene-wrapped nanoparticles to achieve ultra-low friction of the carbon film. This tribocatalytic method provides some inspiration for in situ compensation of friction-induced graphitization of DLC thin films. However, the existing technology does not involve the inhibition of friction-induced graphitization of DLC films. On the contrary, it uses friction to catalyze the transformation of carbon films into ordered graphene structures to wrap nano-metal particles and achieve a ball-like anti-friction effect.

Contents of the invention

The purpose of the present invention is to provide a method for suppressing the phase transition of DLC film friction-induced graphitization, which can solve the problem of wear resistance degradation of DLC film caused by in-situ compensation of friction-induced graphitization by means of tribocatalytic effect.

The above-mentioned technical purpose of the present invention is achieved by the following technical scheme: a kind of DLC thin film friction-induced graphitization phase change suppression method comprises the following three steps:

S1: preparing DLC film;

S2: configure lubricants containing palladium nanoparticle additives;

S3: Carry out in-situ construction of carbon-based thin films containing nano-palladium.

The present invention is further set as follows: the specific operation of preparing the DLC film in step S1 is as follows: first, the surface of the DLC film to be deposited is polished with sandpaper, and then the surface impurities are removed by ultrasonic cleaning; finally, the carbon plate is used as the anode, the stainless steel is used as the cathode, and absolute ethanol is used. As a carbon source, the DLC film was deposited in a constant temperature water bath with a deposition voltage of 300V, an electrode spacing of 2mm, and a temperature of 50°C.

The present invention is further set as follows: in step S2, the lubricant containing palladium nanoparticle additive is configured as follows: the palladium nanoparticle is added to 150N base oil and ultrasonically dispersed, and the palladium nanoparticle additive lubricant is prepared.

The present invention is further set as follows: in step S3, the specific operation of in-situ construction of nano-palladium-containing carbon-based film processing is as follows: the DLC-containing film sample prepared in S1 and the bearing steel form a friction pair, wherein the lower sample is a DLC-containing film The sample of the thin film, the upper sample is a bearing steel ball, the contact load is 0.33GPa, the linear velocity is 0.05-3m/s, the friction treatment is carried out at room temperature, the lower sample is rotated during the friction process, and the upper sample is fixed.

The present invention is further set as follows: the in-situ construction of nano-palladium-containing carbon-based film treatment adopts oil pool lubrication, the lubricating oil containing palladium nano-particle additives configured in S2 is used as a lubricant, and the 150N base oil is a reference oil sample. During friction operation, palladium nanoparticles catalyze the dehydrogenation of base oil molecules to break chains, and in situ form a carbon-based friction film containing nano-palladium on the surface of the DLC film.

In summary, the present invention has the following beneficial effects:

1. The present invention utilizes the complex friction environment (high shear, friction flash temperature, friction emission of low-energy external electrons, etc.) to drive the tribochemical catalytic reaction of the friction system. In a complex friction environment, palladium nanoparticles catalyze the dehydrogenation of the base oil, and the chain scission forms a friction film on the friction surface, thereby inhibiting the graphitization phase transition of the friction-induced DLC film.

2. The method of the present invention not only breaks through the problem of degradation of the anti-wear performance of the DLC film due to the irreversible graphitization induced by friction, but also has the advantages of simple operation, no need to stop or disassemble the machine.

3. The operation of the present invention is simple and feasible, and is of great value in reducing the wear of DLC films and prolonging their service life, and is especially suitable for the lubrication of long-life and high value-added friction systems containing DLC films.

Description of drawings

Fig. 1 is a comparison chart of the Raman spectrum of the DLC film of the present invention after frictional operation for 22 hours under the lubrication of 150N base oil. (a) Raman spectrum outside the wear scar of DLC film; (b) Raman spectrum inside the wear scar of DLC film;

Fig. 2 is the Raman spectrum comparison diagram of the DLC film after friction operation for 22 hours under the lubrication of the palladium nanoparticle additive added in the 150N base oil of the present invention. (a) Raman spectrum outside the wear scar of DLC film; (b) Raman spectrum inside the wear scar of DLC film;

Fig. 3 is a TEM picture of the wear scar cross-section of the DLC film after the friction and wear experiment of the present invention. (a) TEM image of the cross-section of the wear scar; (b) high-resolution TEM image of the friction film;

Fig. 4 is the friction coefficient comparison curve of the present invention from running-in to stable stage (10 hours).

Detailed ways

The present invention will be described in further detail below in conjunction with accompanying drawings 1-4.

Embodiment: a kind of DLC thin film friction-induced graphitization phase change inhibition method, firstly with 60-3000 mesh sandpaper, the surface of the DLC thin film to be deposited is polished, then ultrasonic cleaning 5min removes surface impurities; finally with carbon plate as anode, 304 stainless steel as For the cathode, use absolute ethanol with a volume fraction of 10% as a carbon source, and deposit a DLC film for 3 hours in a constant temperature water bath with a deposition voltage of 300V, an electrode spacing of 2mm, and a temperature of 50°C.

Add palladium nanoparticles with a particle size of less than 100nm into 150N base oil and ultrasonically disperse them for 5 minutes to configure a lubricant with a mass fraction of palladium nanoparticle additives of 0.5%.

The prepared DLC-containing film samples and bearing steel were used to form a friction pair, wherein the lower sample was a sample containing DLC film, the upper sample was a bearing steel ball, and the applied load was 0.33 GPa. Nano-palladium, the average linear velocity is 0.1125m/s, the lower sample rotates during the friction process, and the upper sample is fixed.

Oil pool lubrication was used in the friction experiment, and 150N base oil and lubricating oil containing palladium nanoparticle additives were used as lubricants respectively, and the experiment was run for 22 hours.

The method for preparing DLC film in the present invention includes but not limited to preparation by electrodeposition method, for example physical vapor deposition (PVD), chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD) etc. all can realize the preparation of DLC film.

The particle size of the palladium nanoparticles added to the lubricant includes but is not limited to less than 100nm.

The mating material for the DLC-containing film friction system involved in this method includes but is not limited to bearing steel.

The paraffinic base oils used in the present invention include, but are not limited to, 150N base oils.

The nano-lubricating additives involved in the present invention include but are not limited to Pd, and also include Pt, Au and their composites having tribochemical catalytic properties similar to Pd.

working principle:

As shown in Figure 1 and Figure 2, through the Raman spectrum characterization analysis of the outer (a) and inner (b) of the wear scar, the _ID / The _IG value increased relative to the area outside the wear scar (see Figure 1), indicating that the DLC film was graphitized due to the friction heating and shearing during the friction process. However, when the lubricant containing palladium nanoparticle additives is used in the friction experiment, the I _D / I _G value of the Raman spectrum in the wear scar of the DLC film is reduced compared to the area outside the wear scar (see Figure 2), which shows that in the The addition of palladium nanoparticle additives to the base oil can effectively inhibit the friction-induced graphitization phase transition of the DLC film.

As shown in Figure 3, through the analysis of the TEM image of the cross-section on the wear scar of the DLC film, combined with the change of the I _D / _IG value of the Raman spectrum inside and outside the wear scar in Figure 2, it shows that the complex friction environment can drive the palladium nanoparticles to catalyze the base oil breaking. Chain dehydrogenation forms an amorphous carbon-based tribofilm containing sp2 and sp3 phases. On the one hand, the sp3 phase content of the generated carbon-based friction film is relatively high, which can compensate for the friction-induced graphitization phase transition of the DLC film; on the other hand, the formation of the friction film can reduce the friction coefficient of the friction pair (see Figure 4 ), reduce the impact of friction heating and shearing on the DLC film, thereby inhibiting the friction-induced graphitization phase transition of the DLC film; in addition, the reduction of the friction coefficient can reduce energy consumption.

This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contribution as required after reading this specification, but as long as they are within the rights of the present invention All claims are protected by patent law.

Claims (5)

1. A DLC film friction induced graphitization phase change inhibition method is characterized in that: the method comprises the following three steps:

s1: preparing a DLC film;

s2: preparing a lubricant containing palladium nanoparticle additives;

s3: and constructing a nano palladium-containing carbon-based film in situ.

2. The DLC film friction-induced graphitized phase change inhibition method according to claim 1, characterized in that:

the specific operation for preparing DLC film in step S1 is as follows: firstly, polishing the surface of a DLC film to be deposited by sand paper to remove an oxide layer, and then ultrasonically cleaning to remove surface impurities; finally, taking a carbon plate as an anode, taking stainless steel as a cathode, taking absolute ethyl alcohol as a carbon source, depositing at 300-900V with a polar distance of 2-6mm, and depositing in a constant-temperature water bath at 45-55 ℃ for 2-5h to obtain the DLC film.

3. The DLC film friction-induced graphitized phase change inhibition method according to claim 1, characterized in that:

the specific operation of the lubricant for preparing the palladium-containing nanoparticle additive in the step S2 is as follows: adding palladium nano-particles into 150N base oil, and performing ultrasonic dispersion to prepare the lubricant containing 0.01-2.5% of nano-palladium particles by mass.

4. The DLC film friction-induced graphitized phase change inhibition method according to claim 1, characterized in that:

in step S3, in-situ construction of the nano palladium-containing carbon-based film is carried out, and the specific operation is as follows: and (3) forming a friction pair by the DLC film sample prepared in the step (S1) and bearing steel, lubricating the boundary, and carrying out friction treatment at room temperature under the contact stress of 0.1-1 GPa.

5. The DLC film friction-induced graphitized phase change inhibition method according to claim 4, characterized in that: and in the friction treatment, the nano palladium-containing lubricant configured in the step S2 is used as a lubricant, and under the catalysis of nano palladium, the base oil molecules are dehydrogenated, broken and recombined on the surface of the DLC film to form the nano palladium-containing carbon-based friction film in situ.

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