【作者】 赵金龙；

【导师】 邓建新；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 本文利用中频磁控溅射与多弧离子镀相结合的工艺在硬质合金和高速钢基体上沉积制备出了MoS₂／Zr系列“软”涂层刀具，并对涂层刀具的设计理论、涂层结构、制备工艺、物理机械性能、表面形貌和界面结合机制、摩擦磨损特性及切削性能进行了系统深入的研究。建立了基于残余热应力的涂层与基体材料的物理相容性分析模型，深入分析了基体材料的物理性能参数和沉积温度对涂层刀具残余热应力的影响及其分布规律。结果表明：涂层与基体之间热膨胀系数的差异是影响涂层残余热应力大小的主要因素。通过物理化学相容性分析，确定了与MoS₂“软”涂层材料相匹配的两种最佳基体材料，分别为YT15硬质合金和M2高速钢。分析了过渡层对涂层残余热应力的影响。结果表明：在YT15基体与MoS₂涂层之间添加过渡层后，涂层的残余热应力值均较纯MoS₂涂层的残余热应力值显著降低，其中尤以添加Zr过渡层时涂层的残余热应力值最小；而在M2基体与MoS₂涂层之间添加Ti、Cr或Zr过渡层后，涂层的残余热应力值反而较纯MoS₂涂层的残余热应力值有所增大。因此，应根据不同涂层与基体材料的组合，选择合适的过渡层材料，以达到降低涂层刀具残余热应力的目的。采用中频磁控溅射与多弧离子镀相结合的工艺成功制备了MZ-1（MoS₂／Zr+YT15硬质合金）和MZ-2（MoS₂／Zr+M2高速钢）两种“软”涂层刀具。考察了前处理工艺对涂层性能的影响。结果表明：采用研磨抛光+超声波清洗的前处理工艺能够改善涂层与基体之间的界面结合状态。研究了制备工艺参数对涂层性能的影响，得出了基体负偏压、靶电流、沉积温度和沉积时间对涂层的硬度、厚度、界面结合力及表面粗糙度等的影响规律，确定了两种涂层刀具的最佳制备工艺参数，即对于MZ-1涂层刀具：基体负偏压-200 V，MoS₂靶电压700 V，Zr靶电流60 A，工作气压0．45 Pa，沉积温度200℃，沉积时间120 min；对于MZ-2涂层刀具：沉积温度150℃，其他参数与MZ-1相同。系统地研究了MoS₂／Zr“软”涂层刀具的物理机械性能和界面结合机制。结果表明：MZ-1刀具的涂层厚度2．4μm，硬度10．0 GPa，涂层与基体的界面结合力60 N；MZ-2刀具的涂层厚度2．6μm，硬度9．4 GPa，涂层与基体的界面结合力63 N；两种涂层的硬度和与基体之间的结合力均较纯MoS₂涂层的硬度和结合力有显著提高。通过对MoS₂／Zr“软”涂层刀具的表面形貌、微观结构和界面结合机制的分析可知，用中频磁控溅射与多弧离子镀相结合的工艺制备的MoS₂／Zr“软”涂层表面较为平整，涂层呈现非晶态结构，涂层中各元素分布均匀，涂层与基体材料存在由相互扩散形成的“伪”扩散层，使得涂层与基体的界面结合较为紧密。系统地研究了MoS₂／Zr“软”涂层刀具材料的摩擦磨损特性，探讨了载荷、摩擦距离等对其摩擦磨损性能的影响。结果表明：当分别与45#钢和Al₂O₃球对摩时，MZ-1和MZ-2涂层的摩擦系数随摩擦距离的增大而增大，随载荷的增大而减小；磨损率随载荷的增大而增大。与纯MoS₂涂层相比，MZ-1和MZ-2涂层的摩擦系数和磨损量均显著降低。对摩擦球表面磨损形貌和成分的分析表明，MoS₂／Zr“软”涂层材料与对摩材料表面之间所形成的转移润滑膜是影响材料摩擦磨损性能的关键因素之一。由于摩擦副间转移膜的存在，涂层和对摩材料的摩擦转变为涂层和转移膜之间的“内”摩擦，从而降低了摩擦过程的摩擦系数，提高了材料的耐磨性能。对MoS₂／Zr“软”涂层刀具的切削性能进行了试验研究，并与未涂层的YT15硬质合金刀具和M2高速钢刀具进行了对比。结果表明：加工调质45#钢时，MZ-1涂层刀具的前刀面摩擦系数和切削力均小于未涂层刀具，刀具的耐磨损能力获得提高；钻削45#钢的试验结果表明，MZ-2涂层刀具的后刀面磨损量降低，刀具的磨损程度减轻。试验同时发现，切削速度对MZ-1涂层刀具的磨损性能产生重要影响。低速切削时，涂层刀具的切削性能优于未涂层刀具；当切削速度增大，由于切削过程中产生的切削热和机械应力的作用，涂层出现分层剥落，从而加剧了刀具的磨损。通过对MoS₂／Zr“软”涂层刀具切削加工润滑机理的分析可知，无论是在润滑膜完整的状态抑或边界润滑状态下，由于表面“软”涂层的存在，涂层刀具的摩擦力和摩擦系数均降低；MoS₂／Zr“软”涂层在刀具和切屑之间起到润滑剂的作用，从而降低了刀具的磨损。更多还原

【Abstract】 MoS₂/Zr self-lubricating coated tools were developed by medium-frequency magnetron sputtering combined with multi-arc ion plating technique on cemented carbide and high speed steel substrates. Tribological behaviors and wear mechanisms were detailed studied as well as its design theory, coating structures, deposition process parameters, mechanical properties and cutting performance.The finite element method （FEM） modeling for thermal residual stress analysis of the coatings was established and used to analyze physical compatibility of coating and substrate. The effect factors of the residual stress inside the coated tools such as substrates’ physical parameters and deposition temperature were analyzed. Results indicated that residual stresses of coated tools are mainly affected by substrates’ thermal expansion coefficient and Young’s modulus, while substrates’ Poisson ratio has little effect to residual stress. The optimum substrate materials matched with MoS₂ coating were selected afterwards, they were YT15 cemented carbide and M2 high speed steel, respectively. The FEM analysis results indicated that the residual stress on interface of the coated tools could be decreased by using suitable interlayer material. For MoS₂ coating deposited onto YT15 cemented carbide substrate, the residual stress with Zr interlayer is much smaller than that with Ti or Cr interlayer, while for MoS₂ coating deposited onto M2 high speed steel substrate, any interlayer （Ti/Cr/Zr） was not advised used.The soft coated MZ-1 （MoS₂/Zr+YT15） and MZ-2 （MoS₂/Zr+M2） tools were successfully developed by medium-frequency magnetron sputtering coupled with multi-arc ion plating technique. The optimum parameters （working gas （Ar） pressure: 0.45Pa; substrate bias: -200 V; MoS₂ target voltage: 700 V; Zr target arc current: 60 A; deposition time: 120 min; deposition temperature: 200℃=（for MZ-1） and 150℃（for MZ-2））. Fore treatment process of coated tools was studied. The results indicated that fore treatment process of polishing and ultrasonic cleaning can improve adhesion strength between the coating and substrate.The physical and mechanical properties of MZ-1 and MZ-2 coated tools were roundly studied. The structure of MZ-1 and MZ-2 coated tools is dense and coating elements are distributed equably. The coating micro-hardness is 10.0 GPa and 9.4 GPa both of which are higher than that of pure MoS₂ coating, and the adhesion strength is 60 N and 63 N, respectively, corresponding to MZ-1 and MZ-2 tools. The coating thickness of MZ-1 and MZ-2 is 2.4 and 2.6 urn, respectively. The interface adhesion mechanism of MZ series coatings and substrates is an interaction of mechanical occlusion and diffusion.The effect of load and friction distance on the friction and wear behavior of MoS₂/Zr coated materials sliding against 45# steel and Al₂O₃ ball was studied, respectively. The experiment results showed that the friction coefficient of MoS₂/Zr coated materials increases with increasing of friction distance, and decreases with increasing load. The wear rate increases with increasing load. Both friction coefficient and wear rate are much smaller than that of pure M0S2 coating. EDX analyses for the surface of coated tools and counterpart ball indicated that there was transfer layer formed, which was found to play an important role in reducing the friction coefficient and wear rate of MoS₂/Zr coated tools.The cutting performance of MoS₂/Zr coated tools was studied, and compared with YT15 cemented carbide and M2 high speed steel uncoated tools. The experimental results indicate that deposition of MoS₂/Zr soft coating onto YT15 and M2 tools shows decreased friction coefficient and flank wear compared with those of uncoated tools when dry cutting 45# quenched steel. Cutting speeds were found to have a profound effect on the wear behaviors of MoS₂/Zr coated tools. In case of low speed cutting, the MoS₂/Zr coated tools showed much better cutting performance compared to the uncoated tools, in high speed cutting processes, delamination of coating occurred owing to the elevated cutting temperature, which may initiate the loss of the coating from the rake face, and lead the increase of the tool wear.更多还原