| ince stainless steel was invented by the English metallurgist Henry Blair during theFirst World War,it became one of the most popular green material for its advantages,such as the long serving life,the low life cycle cost,recyclable material and the pleasing appearance.Now it has been widely used in every area.Recently aerospace industry,marine machineries and energy industry have developed rapidly,so stainless steel need to have better performance,especially its wear-friction properties.The experiment was operated in the arc ion plating system,1Cr17Ni2 martensitic stainless steel and 18-8 model 304 austenitic stainless steel were performed surface plasma nitriding by a wire reinforced plasma,the surface morphology,composition,phase structure and mechanical properties of nitrided sample were characterized and analysised,expect to get gradually reinforced surface properties.Lay the foundation for the further reinforcing.Then the DLC coating was deposited using the carbon target in the arc ion plating system to get the modified layer with high hardness and low friction coefficient to improve the surface overall properties.At first,1Cr17Ni2 martensitic stainless steel was performed surface plasma nitriding by a wire reinforced plasma in the arc ion plating system.The surface morphology,composition,phase structure and mechanical properties of nitrided sample were characterized and analysised.The results showed the surface hardness of the nitrided stainless steel sample improved from 3.67 GPa to 9.25 GPa,and kept above 7.32 GPa at the depth range below 50μm,which was attributed to the formation of new phases such as Cr N and Fe2 N.While compared to the substrate,the friction coefficient of nitrided sample only decreased from 1.1to 0.9,failed to get the expected tribological behavior;the nitrided 304 austenitic stainless steel also has the reinforced properties,the surface hardness of the nitrided stainless steel sample improved from 3.67 GPa to 6.13 GPa,kept above 5.32 GPa at the depth range below30 μm,the surface friction coefficient only decreased from 1.1 to 0.8,failed to get the expected tribological behavior,either.Then,on the basic of nitrided pretreatment,the DLC coating was deposited on the two kinds of stainless steel using the carbon target in the arc ion plating system.The resultsshowed when the composite treatment was conducted,high quality DLC coating with a thickness of 1.5 μm was successfully synthesized.The nitrided pretreatment made the surface hardness improve gradually,the hardness further increased to 17.06 GPa and the friction coefficient significantly reduced to 0.09,obtained obvious results on strength and friction-reducing properties;so the same as 304 austenitic stainless steel,the surface hardness improved gradually at the depth range below 31.5 μm,improved from 3.64 GPa to 5.31 GPa and then to 15.83 GPa,the friction coefficient significantly reduced to 0.08,obtain the desired properties. |
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