High Temperature Friction and Wear Behaviours of Ceramic Films by CVD
The TiN/TiCN,TiN/Al2O3 and TiN/TiCN/Al2O3 ceramic films were prepared by chemical vapor deposition on mechanically polished H13 alloy steel to study the high temperature wear resistance. The adhesion,hardness and high temperature wear resistance at 600 ℃ of the three films were characterized and evaluated by means of scratch test,microhardness test and high temperature friction and wear test,and the wear morphology was analyzed by scanning electron microscope and optical microscope. The results showed that the outermost layer of the TiN/TiCN film showed an inverted pyramid shape,and the film thickness was about 8.8 μm. The outermost layer of the TiN/Al2O3 film had a loose structure and small pores were observed. The inverted pyramid grain was embedded into the film,and the film thickness was about 3.0 μm. The surface of TiN/TiCN/Al2O3 film presented particle cluster structure,and the thickness was about 10.8 μm. The three ceramic films prepared by CVD had dense structure,no pores,cracks and other defects,and had good bonding interface with the substrate. The TiN/TiCN/Al2O3 multilayer film had the best bonding strength with the substrate,which was 68.53 N and might be due to the good hardness gradient formed between TiN,TiCN and Al2O3. However,the bonding strength between the surface Al2O3 film and the middle layer TiCN film was weak. The results of high temperature friction and wear at 600 ℃ showed that TiN/Al2O3 film had the highest high temperature friction coefficient,with an average value of 0.51,but its high temperature wear resistance was the best and the volume wear rate was 0.58×10-5 mm3/(N·m). The TiN/TiCN film had the lowest high temperature friction coefficient,with an average value of 0.37,but its high temperature wear resistance was the worst and the volume wear rate was 4.23×10-5 mm3/(N·m). The main damage forms of the three ceramic films at high temperature were different. The main wear mechanisms of the TiN/TiCN films were adhesive wear,oxidation wear and fatigue wear. The main wear mechanism of the TiN/Al2O3 film was abrasive wear. The main wear mechanisms of the TiN/TiCN/Al2O3 multilayer film were abrasive wear and oxidation wear. The best high temperature wear resistance of the TiN/Al2O3 film was due to its high hardness and stable chemical properties and the main wear form was abrasive wear,which is difficult to be removed by wear. The high temperature wear resistance of the TiN/TiCN/Al2O3 multilayer film was worse than that of TiN/Al2O3 film,which might be due to the hard fragments formed when the high-hardness Al2O3 layer was worn off,having obvious cutting effect on the softer TiCN layer and increasing the wear rate of the multilayer film. The worst high temperature wear resistance of the TiN/TiCN film was due to the low hardness of TiCN film. Under the high temperature friction,it might lead to oxidative wear,adhesive wear,fatigue wear and other damage forms. EDS and Raman analysis results of the wear scar indicated that obvious oxidation wear occurred on the TiCN film during high temperature friction and wear,and the friction product was TiO2.
chemical vapor depositionceramic filmhigh temperature friction and wearbonding strengthwear resistancewear mechanism
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