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40Cr表面多弧离子镀TiAlN/TiN复合膜层的工艺及性能研究
【作者】 蒋涛；
【导师】 严铿；
【作者基本信息】 江苏科技大学 ， 材料加工工程， 2010， 硕士
【摘要】 机械传动装置中,齿轮的失效占到失效总数的绝大部分,齿轮在传动过程中的受到弯曲应力、接触应力、冲击力等多种力的综合作用,产生的失效形式多种多样。传统的表面强化工艺（整体淬火、表面淬火、氮化等）逐渐不能满足工业生产的需要,新型表面强化技术（PVD、CVD）正受到越来越多人的关注。本文主要利用多弧离子镀技术在常用齿轮钢40Cr表面制备TiAlN/TiN膜层,研究不同工艺参数对膜层的表面形貌、内部组织结构、显微硬度、抗氧化性能及摩擦磨损性能的影响。制备TiAlN/TiN膜层所采用的靶材为纯度为99.99%纯铝靶和工业级纯钛靶,镀膜参数为基体负偏压0～500V,钛靶电流60A,铝靶电流40～80A,N2分压0.3～1.3Pa,沉积温度200℃,镀制时间90min。研究结果表明:基体负偏压对膜层性能有很大的影响,过高或过低的基体偏压会使得膜层表面不平整,表面显微硬度降低。基体负偏压越高,膜层中Ti、Al原子的含量就越低;靶材电流对膜层性能也有显著影响,电流越高膜层表面越不平整。显微硬度则随着靶材电流的升高而先上升后降低。电流越高,膜层中Ti、Al原子的含量就越高;N2分压的升高对改善膜层表面形貌起有利的影响,但是过高的N2分压也会导致靶材表面“氮中毒”,使得膜层显微硬度下降,膜层中Ti、Al原子的含量下降。TiAlN/TiN膜层的抗氧化性能要大大优于40Cr基体和TiN膜层。在200℃空气环境中,40Cr基体表面已经出现十分明显的氧化痕迹。温度到700℃时,表面生成的氧化皮明显增厚并开裂脱落,完全不能保护基体。TiN膜层在200℃空气环境中显示出的抗氧化性能较好,但到700℃时,TiN薄膜被完全氧化,颜色从本来的金黄色变为棕色并且表面出现剥落,露出基体。TiAlN/TiN膜层无论在200℃还是700℃的环境中都表现出了优异的抗氧化性能,膜层完整,无开裂,无剥落。研究TiAlN/TiN膜层在干态旋转滑动条件下的摩擦磨损性能的主要试验参数为:法向载荷10～30N,线速度13188mm/min,持续时间10min。通过对比40Cr在相同条件下的试验结果我们发现,TiAlN/TiN膜层的摩擦系数和磨损量都要大大低于40Cr。同时我们还发现随着法向载荷的增大膜层的摩擦系数呈下降趋势。
【Abstract】 Gear failure takes the most important part of the failure of mechanical drive. When the gear is transfering power, it has to bear bending stress, contact stress and impact stress. So, the gear has a lot of failure modes. The conventional surface strengthening techniques such as whole quenching, surface quenching and nitride can not meet the needs of industrial production. The new surface strengthening techniques such as PVD and CVD have been concerned by people.40Cr steel substrate is coated with TiAlN/TiN films by Multi-arc ion technology. We study surface morphology, internal structure, microhardness, oxidation resistance and friction and wear properties of TiAlN/TiN coating in different process parameters. The butt materials are 99.99% purity titanium and 99.99% purity aluminum. The deposition parameters are as follows: pushed biasing is 0500V, current of titanium target is 60A, current of aluminum target is between 40A to 80A, N2 pressure is from 0.3Pa to 1.3Pa, deposition temperature is 200℃and time of coating is 90min.The results show that: the pushed bias voltage has a great influence in performance of TiAlN/TiN films. The excessively high pushed bias voltage can make the surface of films out of flatness and reduce the micro hardness of films. The same to pushed bias voltage if it is excessively low. The content of Ti and Al in films becomes more and more lower if the pushed bias voltage becomes more and higher; the current of titanium target also has a great influence in performance of TiAlN/TiN films. The surface of coating becomes more and more out-of-flatness by increasing of arc. The microhardness of coating is increasing when arc is increasing. But if the arc is too high, it may make the microhardness fall down. The content of Ti and Al in films becomes more and higher by the arc increasing; The higher N2 pressure is from a beneficial effect on improving the surface morphology of TiAlN/TiN films. But if N2 pressure is too high, it can make a phenomenon which we called“Nitrogen poisoning”on the surface of aluminum target and titanium target. The content of Ti and Al in films and microhardness become lower.Oxidation resistance of TiAlN/TiN films is batter than 40Cr and TiN film. 40Cr has been oxidized at 200℃. At 700℃, the oxide scale of 40Cr becomes thickening, cracking and shedding. TiN film has good oxidation resistance at 200℃, but has been oxidized completely at 700℃. TiN film has begun to drop and its color from golden to brown. TiN film can not protect 40Cr steel substrate at 700℃. Oxidation resistance of TiAlN/TiN films is perfect at 700℃. The films are integrity, no cracking and no peeling.The main experimental parameters of reciprocating sliding dry friction experiment are as follows: normal load is between 10N and 50N, linear velocity is 13188mm/min and each time is 10min. After comparing the friction properties of 40Cr and TiAlN/TiN films we find that both friction coefficient and wear loss of TiAlN/TiN films are lower than 40Cr. Meantime we also find that the friction coefficient of TiAlN/TiN films is reducing as the normal load increases.