【作者】 李杰；

【导师】 张世宏； 杨阳；

【作者基本信息】 安徽工业大学 ， 材料科学与工程， 2023， 博士

【摘要】 我国依赖进口的传动件、转动件和主承力构件等核心零部件和关键基础材料已经成为制约高端制造业转型升级的瓶颈,其原因之一在于缺少核心的表面改性技术。非晶碳薄膜因高硬度、低摩擦系数、耐磨损以及高的化学稳定性等优异性能,在金属表面减摩耐磨需求方面具有重要的应用价值。本研究针对非晶碳膜内应力大、与金属基材结合力差的问题,以辉光放电等离子体渗氮/碳为基础,提出了一步法原位构筑扩渗层/类石墨碳（Graphite-like carbon,GLC）膜复合改性层的方法,探索了等离子体扩渗层表面GLC薄膜的生长机制,并在M50Ni L轴承钢表面制备了扩渗层/GLC薄膜复合改性层,揭示了该复合改性层的减摩耐磨机理。本文所取得的主要研究成果如下:（1）在辉光放电等离子体渗氮系统中,选择硅和渗氮钢两种基体,优化了非连续多步法制备GLC薄膜的工艺。研究结果表明,GLC薄膜的厚度和含氢量随电压和占空比的增大而减小。气氛组成对沉积的GLC薄膜的厚度、微观结构和粗糙度有显著影响。过多的H₂引入导致GLC薄膜厚度变薄。随着电压和占空比的增大,GLC薄膜表面由较粗糙的宽山坡状转变为相对平坦光滑的表面,且表面水接触角减小。渗氮钢表面沉积的GLC薄膜的sp²键合含量在71.36%～74.28%范围内可调节,薄膜硬度约为10 GPa,与渗氮层表面硬度接近。电压为700 V、占空比为35%、C₃H₈与H₂的体积流量比为10:15是制备GLC润滑膜的最佳工艺参数。（2）在等离子体渗氮与GLC薄膜沉积复合工艺之间加入了氩离子溅射工艺,研究了该桥接工艺对渗氮层和GLC薄膜微观组织结构的影响。研究结果表明,溅射工艺通过轰击活化了渗氮层表面,提高了表面能,从而促进了后续GLC薄膜的形核生长。氩离子溅射处理增强了GLC薄膜与渗氮层的膜-基结合力。得益于GLC薄膜的自润滑特性、基底渗氮层的梯度硬度对GLC膜良好的支撑以及优异的膜-基结合力,渗氮温度为520°C,氮氢比为3:1的涂层S-2具有最低的摩擦系数（<0.1）和最低的磨损率(0.61×10^-6 mm³ N^-1 m^-1)。（3）连续法原位构筑了渗碳层/GLC薄膜复合层,研究了复合层的组织结构、形成机制及性能。研究结果表明,渗碳层表面原位沉积的GLC薄膜的厚度约900nm,大于碳氮共渗层表面原位沉积的GLC薄膜厚度（约700 nm）。第一性原理计算结果表明,相比较Fe₃C（N）相,GLC薄膜更易在Fe₃C相表面生长,这解释了为什么渗碳层表面GLC薄膜厚度更大。渗碳层与GLC薄膜界面处形成了一种“触角”状纳米复合结构,此结构有利于渗碳层与GLC薄膜的结合。Fe₃C（N）（001）/金刚石（111）界面的最大粘附功(W_ad)为1.53 J/m²,小于Fe₃C（001）/金刚石（111）界面的最大粘附功（1.66 J/m²）,说明Fe₃C（N）（001）/金刚石（111）界面的粘附强度弱于Fe₃C（001）/金刚石（111）界面。虽然从力学角度看碳氮共渗层相较渗碳层是更好的支撑层,但第一性原理计算结果证明界面结构匹配起着决定性作用。（4）连续法原位构筑了渗氮层/GLC薄膜复合层,研究了其组织结构、形成机制及性能。研究结果表明,渗氮层中Fe₃N相的相对含量与沉积的GLC薄膜的厚度及其sp²键合含量均呈正相关。较多的Fe₃N相含量会导致更加粗糙的表面形貌,从而不利于GLC薄膜的原位沉积,这与实际结果是矛盾的。第一性原理计算结果表明GLC薄膜在Fe₃N表面易于形成,而在Fe₄N表面难以形成。即渗氮层表面Fe₃N相作为衬底,对原位沉积的GLC薄膜具有诱导生长作用。样品520-3:1的临界载荷Lc2达到了最大值94.43 N,这主要是由于渗氮层与GLC薄膜界面处形成了包含非晶与纳米晶复合结构组成的有益过渡层组织,这种有益结构相当于一个化学互锁层增强了界面粘附强度。由于GLC薄膜本身的自润滑特性以及最优的界面粘附,样品520-3:1表现出优异的减摩耐磨性能。更多还原

【Abstract】 The core components and critical raw materials（e.g.transmission parts,rotating parts and main bearing components）dependent on imports have been a constraint to transformation and upgrading of high-end manufacturing industry due to the lack of core surface modification technology.Amorphous carbon films have important applications in metal surface friction reduction and wear resistance needs due to their excellent properties such as high hardness,low coefficient of friction,wear resistance and high chemical stability.In this study,in view of the problems of high internal stress of amorphous carbon film and poor bonding with metal substrate,based on the glow discharge plasma nitriding/carbon,a one-step in-situ construction of the duplex modified layer of diffusion layer/graphite-like carbon（GLC）film was proposed,and the growth mechanism of GLC film on the surface of the plasma diffusion layer was explored,and a duplex modified layer of diffusion layer/GLC film was prepared on the surface of M50Ni L bearing steel,which revealed the friction and wear-resistant mechanism of this duplex modified layer.The main research results obtained in this thesis are as follows:（1）In a glow discharge plasma nitriding system,two substrates,silicon and nitrided steel,were selected to optimise the process for the preparation of GLC films in a discontinuous multi-step process.The results show that the thickness and hydrogen content of GLC films decrease with increasing the voltage and the duty cycle.The atmosphere composition had a significant effect on the thickness,microstructure and roughness of the deposited GLC films.Excessive H₂ introduction leads to thinning of GLC film thickness.With increasing voltage and duty cycle,the surface of the GLC films transformed from a rougher broad hillside shape to a relatively flat and smooth surface,and the surface water contact angle decreased.The sp² bonding content of the GLC films deposited on the nitrided steel surface is adjustable in the range of 71.36%～74.28%,and the hardness of the films is approximately 10 GPa,which is close to the surface hardness of the nitrided layer.A voltage of 700 V,a duty cycle of 35%,and a volume flow ratio of C₃H₈ to H₂ of 10:15 were the optimum process parameters for the preparation of GLC lubrication films.（2）An argon ion sputtering process was incorporated between the plasma nitriding and GLC film deposition composite processes,and the effects of this bridging process on the microstructure of the nitrided layer and GLC films were investigated.The results showed that the sputtering process activated the surface of the nitrided layer by bombardment and increased the surface energy,which promoted the subsequent nucleation growth of the GLC films.The argon ion sputtering treatment enhanced the film-substrate bonding between the GLC film and the nitrided layer.Benefiting from the self-lubricating property of the GLC film,the good support of the GLC film by the gradient hardness of the substrate nitrided layer,and the excellent film-substrate bonding,the coating S-2 with a nitriding temperature of 520°C and a nitrogen/hydrogen ratio of 3:1 has the lowest COF（<0.1）and the lowest wear rate(0.61×10^-6 mm³ N^-1 m^-1).（3）A carburised layer/GLC film duplex layer was constructed in-situ by a continuous method,and the organisation,formation mechanism and properties of the duplex layer were investigated.The results show that the thickness of the GLC film deposited in-situ on the surface of the carburised layer is～900 nm,which is greater than that of the GLC film deposited in-situ on the surface of the carbonitrided layer（～700 nm）.First-principle calculations show that the GLC films are more likely to grow on the surface of the Fe₃C phase compared to the Fe₃C（N）phase,which explains why the thickness of the GLC films on the surface of the carburised layer is larger.At the interface between the carburized layer and the GLC film,an"antenna"nanocomposite structure is formed,which facilitates the bonding of the carburized layer with the GLC film.The maximum work of adhesion(W_ad)at the Fe₃C（N）（001）/diamond（111）interface is 1.53 J/m²,which is smaller than that at the Fe₃C（001）/diamond（111）interface（1.66 J/m²）,indicating that the adhesion strength at the Fe₃C（N）（001）/diamond（111）interface is weaker than that at the Fe₃C（001）/diamond（111）interface.Although from the mechanical point of view the carbonitrided layer is a better support layer compared to the carburized layer,the results of the first-principle calculations prove that the matching of the interface structure plays a determinative role.（4）The nitrided layer/GLC thin film duplex layer was constructed in-situ by the continuous method,and its organisation,formation mechanism and properties were investigated.The results show that the relative content of Fe₃N phase in the nitrided layer is positively correlated with both the thickness of the deposited GLC film and its sp² bonding content.A higher content of Fe₃N phase leads to a rougher surface morphology,which is not favourable for the in-situ deposition of GLC films,which is contradictory to the obtained results.First principle calculations show that GLC films are easy to form on the Fe₃N surface and difficult to form on the Fe₄N surface.That is,the Fe₃N phase on the surface of the nitrided layer acts as a substrate and induces growth of the in-situ deposited GLC films.The critical load Lc2 of sample 520-3:1 reaches a maximum value of 94.43 N,which is mainly due to the formation of a beneficial transition layer organisation containing amorphous and nanocrystalline composite structures at the interface between the nitrided layer and the GLC film,which is equivalent to a chemically interlocked layer that enhances the interfacial adhesion strength.Due to the self-lubricating property of the GLC film itself and the optimal interfacial adhesion,the sample 520-3:1 exhibits excellent friction and wear reduction properties.更多还原