离子源增强电弧离子镀活塞环表面CrN涂层的制备

摘要

In order to develop environment-friendly coatings to replace galvanic coatings electroplated on the piston rings of engine parts,a home-made anode ion source assisted cathodic arc plating system was used to deposit CrN coatings with different thicknesses on W 18Cr4V high speed steel substrates.The structure,surface morphology and thickness of the coating were measured by XRD and SEM.The micro-hardness tester and the ball-on-disk friction tester were applied to study the mechanical properties.The results show that the crystal structure of the CrN coatings does not obviously change with thickness increasing.The micro-hardness of 2.5μm CrN coatings is about 1 900 HV0.05.However,the thickness of CrN coatings obviouly influences the tribological properties.The lowest friction coefficient and wear rate are 0.6 and 2.664× 10-6 mm3/N.m,respectively.Honing testing was used for comparing properties of the CrN and galvanic chromium coatings deposited on ASL817 steel piston rings.The CrN coated piston rings show larger size void of 50 μm and no cracking or dropping after 2 400 times honing,and the working gaps has no obviously changing.The wear and working gaps of electrolytic Cr-coated piston rings are worse than CrN coated piston rings after 2 400 times honing.The normal working gaps can be achieved after 12 000 times honing,whereas the electrolytic Cr-coated piston rings have evident failure because of the larger gaps.%为了寻求发动机核心部件活塞环上电镀硬铬的替代技术,采用自行设计的离子源增强阴极电弧离子镀系统,在W 18Cr4V高速钢试块上制备了不同厚度的CrN涂层,用XRD、SEM分析涂层的晶体结构、表面形貌和厚度;利用显微硬度计和球盘式摩擦仪分析了涂层厚度对力学性能的影响.结果表明:随着厚度的增加,CrN涂层结晶结构没有明显变化,2.5 μm厚CrN涂层硬度达1 900 HV0.05,最低摩擦因数0.6,最低磨损速率2.664× 10-6 mm3/N.m.对CrN涂层和电镀硬铬ASL817钢质活塞环进行珩磨测试,在珩磨2 400次之后,CrN涂层钢质活塞环出现较大孔洞(50 μm),但没有涂层脱落,具有良好的附着力,工作间隙变化不大;电镀硬铬活塞环涂层磨损较CrN涂层严重,工作间隙开始变大;珩磨12 000次后电镀硬铬活塞环工作间隙达到允许最大值,CrN涂层活塞环依保持正常工作间隙,耐磨性更好.