【作者】 吴凤芳；

【导师】 邓建新；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 在许多工程领域,固体粒子的冲蚀磨损是个严重的问题。涂层作为零部件表面的屏障,可以有效地保护处在冲蚀环境中工作的零部件,免受固体粒子的冲蚀。物理气相沉积(PVD)是一种适用于制备较小厚度涂层且对基体材料的力学性能影响很低的涂层技术。因而,近年来,利用PVD涂层来提高零部件的抗冲蚀性能成为涂层应用中的一个研究热点。本文采用PVD技术制备了TiAIN、CrN、CrAIN、CrAlTiN涂层,对这些氮化物涂层的冲蚀磨损特性和磨损机理进行了研究。以硬质合金WC/TiC/Co、WC/Co和不锈钢1Cr18Ni9Ti三种材料为基体,采用离子束辅助真空脉冲过滤弧沉积技术制备TiN、TiAIN、CrN和CrAIN四种涂层,采用非平衡磁控溅射技术沉积CrAlTiN涂层。通过对涂层的相组成、组织形貌、元素分布和微区成分的分析,以及对涂层的晶体学结构与结合界面的微观形貌的研究,发现涂层的主要相组成为相应的氮化物,涂层致密,涂层元素分布均匀,涂层与基体结合良好,涂层与基体中某些元素在界面处存在相互扩散,涂层与基体界面结合机制为机械结合与元素的相互扩散。对涂层的物理机械性能进行了检测,得到涂层的厚度、显微硬度、弹性模量、结合力及残余应力等性能参数。在所研究的氮化物涂层中,以TiAIN涂层的显微硬度最高,硬度值为32.40GPa, CrN涂层的硬度值最低,只有16.50GPa; TiAIN弹性模量最高为580GPa, CrN涂层的弹性模量最低,仅有360 GPa；以WC/Co基体上CrAIN涂层的结合力最高,其值为88.56 N,以WC/Co基体上CrAlTiN涂层的结合力最低,为48.36 N；硬质合金基体上涂层的残余应力均为压应力,而不锈钢基体上涂层的残余应力多为拉应力。通过对涂层冲蚀磨损试验结果的分析,揭示了不同基体上各涂层的冲蚀磨损特性。WC/TiC/Co基体上四种涂层与基体的冲蚀磨损率由低到高的顺序为TiAlN<CrAlN<WC/TiC/Co<TiN<CrN, TiAIN涂层的冲蚀磨损率约为WC/TiC/Co的1/4倍;WC/Co基体上四种涂层与基体的冲蚀磨损率由低到高的顺序为CrAlN<TiAlN<CrAlTiN<TiN<WC/Co,其中CrAIN涂层的冲蚀磨损率为WC/Co的1/3；1Cr18Ni9Ti基体上四种涂层的冲蚀磨损率由低到高的顺序为CrAIN<TiAIN<CrAlTiN<TiN<1Cr18Ni9Ti, 1Cr18Ni9Ti蚀磨损率是CrAIN涂层的3.9倍。通过对涂层物理机械性能与冲蚀磨损性能的关系进行分析,揭示了涂层机械性能对冲蚀磨损性能的影响,发现涂层的硬度和弹性模量对涂层冲蚀性能的影响不是单因素作用,而是综合起作用。通过分析不同基体材料的特性与涂层冲蚀磨损率的关系,揭示了基体材料性能对涂层冲蚀性能的影响规律。研究发现涂层冲蚀性能并不取决于基体硬度,基体弹性模量与涂层弹性模量相当时,涂层冲蚀率较低。通过对涂层表面微观形貌的观察与分析,研究了各涂层的冲蚀表面形貌特征,发现冲蚀破坏开始于涂层表面组织的生长缺陷。用离子束辅助真空脉冲过滤弧技术沉积涂层的破坏从涂层表面的宏观粒子和空穴开始,采用磁控溅射技术沉积涂层的破坏从表面的空穴开始。基于压痕断裂力学理论,建立了尖锐粒子冲蚀条件下涂层冲蚀磨损模型,并结合涂层的冲蚀形貌,分析了该模型的有效性。对单个尖锐粒子冲蚀条件下涂层材料的去除体积进行了分析,用涂层的机械性能参数硬度H和弹性模量E来描述单个尖锐粒子冲蚀条件下涂层的去除体积函数,揭示了涂层机械性能对去除体积的影响。通过对涂层冲蚀磨损表面宏观形貌、微观形貌及冲蚀断面微观形貌进行综合分析,揭示了涂层的冲蚀磨损机理。TiN涂层的冲蚀磨损机理以涂层材料的脆性疲劳断裂为主,TiAIN涂层的冲蚀磨损机理随基体不同而有差别：WC/TiC/Co基体上TiAIN涂层材料去除方式主要有微切削和脆性疲劳断裂。WC/Co基体上TiAIN涂层材料去除以脆性疲劳断裂为主；1Crl8N1i9Ti基体上TiAIN涂层,涂层的去除方式有微切削、塑性疲劳断裂和脆性疲劳断裂三种。CrN涂层材料的主要去除机理为脆性疲劳断裂。WC/TiC/Co基体上CrAIN涂层材料的去除机理为脆性疲劳断裂,WC/Co基体上CrAIN涂层冲蚀机理以涂层材料的塑性疲劳断裂为主,1Cr18Nli9Ti基体上CrAIN涂层去除机理主要有两种：微切削和脆性疲劳断裂。CrAlTiN涂层冲蚀磨损机理：开始阶段,涂层材料去除方式以微切削为主,然后转为脆性疲劳断裂。涂层组织缺陷空穴边缘材料的去除也同时有微切削和脆性疲劳断裂两种方式。更多还原

【Abstract】 Erosion wear by solid particles is a serious problem in many engineering fields. Coatings, as the barrier of the parts surfaces, can protect the parts from being eroded by solid particles. Coatings with small thickness are produced suitably using PVD technology, which has very small effects on the mechanical performances of the substrate. Therefore, it has been a hot subject that PVD coatings are used to improve the erosion resistance of parts. TiN, TiAIN, CrN, CrAIN, CrAlTiN coatings were produced by PVD technologies in this investigation. The erosion characteristics and wear mechanisms of the coatings were investigated in this paper.Two hard metals, WC/TiC/Co and WC/Co, and a stainless steel, 1Cr18Ni9Ti were used as substrate materials. Four coatings, TiN, CrN, CrAIN and TiAIN were produced by pulsed filtered vacuum cathode arc deposition assisted with ion bombardment. CrAlTiN coating was deposited using unbalanced magnetron sputtering. Phases, morphologies, elements distributions, compositions of micro fields, crystallographic sequences and interfaces were analysed. It was shown that the main phases were the corresponding nitrides. It was discovered that the coatings were dense and the elements were well distributed. Good bonding exsisted between the coating and the substrate. There was some element diffusion between the substrate and the coating. There were both physics and elementen diffusion bonding between the substrate and the coating. Phasical and mechanical performances of the coatings were measured. The hardest coating was TiAIN coating with hardness of 32.40 GPa and the softed coating was CrN coating 16.50 GPa. The coating with the highest and the lowest elatic modulus was that of TiAIN coating and CrN coating, and their modulus was 580 GPa and 360 GPa respectively. The coating with highest adhension strength is CrAIN coating on WC/Co and the coating with the lowest adhension was CrAlTiN coating, and their adhension strength was 88.56 N and 48.36 N, respectively. The residual stress was compressive for the coatings on the hard metals and tensile for most of the coatings on the stainless steel.It was shown that the erosion wear characteristics of the coatings on different substrates by analyzing the results of the erosion tests. The ranking of the erosion rate of of the substrate WC/TiC/Co and the coatings on it was TiAlN<CrAlN<WC/TiC/Co <TiN< CrN. The erosion rate of the TiAIN coating was only 1/4 times of that of the substrate WC/TiC/Co. The ranking of the erosion rate of the substrate WC/Co and the coatings on it was CrAlN<TiAlN<CrAlTiN<TiN<WC/Co, and the erosion rate of the CrAIN coating was 1/3 times of that of the substrate WC/Co. The ranking of the erosion rate of the substrate 1Cr18Ni9Ti and the coatings on it was CrAIN<TiAIN<CrAlTiN <TiN<1Cr18Ni9Ti, and the erosion rate of the substrate 1Cr18Ni9Ti was 3.9 times of that of the CrAIN coating on it.It was revealed that the effects of the mechanical performances of the coating on its erosion resistance by analyzing their relation.. It was that the union of the hardness and the elstic modulus affected the erosion resistance of the coating instead of the affecting from the hardness or the elastic modulus alone. It was shown that the effects of the substrate performances on the erosion resistance of the coating by analyzing the relation between the characteristics of the substrate material and the erosion rate of the coating. It was discovered that the erosion resistance of the coating was not dependent on the substrate completely. The erosion rate of the coating was much lower as the elastic modulus of the substrate was comparable to that of the coating.The erosion surface morphologies of the coatings were observed. It was found that the erosion damage began from the microstructure defects of the coatings. The coatings deposited by pulsed filtered vacuum cathode arc deposition assisted with ion bombardment were eroded from the growth defects of the microstructure in the coatings surfaces. The coatings deposited by unbalanced magnetron sputtering were eroded from the pits in the surfaces of the coatings.The erosion model was built for angular solid particles based on the theory of indentation fractur mechanics. The volume of the coating material removed by a single angular solid particle was analysed. A function with two mechanical parameters, the hardness and the elstic modulus of the coating, was used to describle the volume of the coating removed by a single solid particle. The effect of mechanical performances on the coating volume removed during the erosion was revealed with this function. The validity of the function was discussed with the erosion morphology of the coating surface.By analyzing the macro and micro morphologies of the erosion surfaces of the coatings and the micro morphologies of the cross-section of the erosion scar, the erosion wear mechanism of the coating was discussed. The main erosion mechanism of the TiN coatings was brittle fatigue fracture of the coating material. The erosion mechanisms of the TiAIN coatings varied with the substrates. The main erosion mechanisms of the TiAIN coating on WC/TiC/Co substrate were micro cutting and brittle fatigue fracture, while the TiAIN coatings on WC/Co substrate was brittle fatigue fracture. The main erosion mechanisms of TiAIN coating on 1Cr18N1i9Ti substrate were micro cutting, ductile fatigue fracture and brittle fatigue fracture. The main erosion mechanism of CrN coating on WC/TiC/Co substrate was brittle fatigue fracture. The main erosion mechanism of coating CrAlN on WC/TiC/Co was brittle fatigue fracture, while the main damage mechanism of coating CrAlN on WC/Co was ductile fatigue fracture. The main erosion mechanism of coating CrAlN on 1Cr18N1i9Ti was micro cutting and brittle fatigue fracture. The erosion mechanism of CrAlTiN coating was micro cutting and brittle fatigue fracture. The coating material at the edge of the pit, which were the growth defect of the coating structure, was removed in the way of micro cutting and brittle fatigue fracture.更多还原