Research On High-temperature And Friction Properties Of Prepared Multilayer TiAlN/AlCrSiN Tool Coatings

Coating technology is often used to improve tool performance and extend tool life.AlCrN is widely used as a tool coating due to its excellent mechanical properties.AlCrSiN is a quaternary coating obtained by doping Si in AlCrN.Si doping makes it form a typical nc-MeN/a-Si₃N₄ structure,which greatly improves the mechanical and friction properties of the coating.However,the alloying of Si and AlCrN will reduce the solid solution limit of the stable c-AlN phase in AlCrN and accelerate the formation of the unstable h-AlN phase,thereby reducing the thermal stability and mechanical properties of the coating.In response to this problem,the TiAlN/AlCrSiN alternating multilayer coatings are designed in this thesis.On the one hand,the"template effect"of the c-TiAlN intercalation layer will induce the formation of c-AlN phase in the coatings,thereby improving thermal stability of coatings.On the other hand,the strong interfacial energy between layers of multi-layer coatings can inhibit the dislocation movement and crack propagation,as well as the diffusion of elements in the coatings.Thus,the high temperature oxidation resistance of the coatings can be improved and the hardness of the coatings after high temperature treatment can be inhibited from decreasing.In this thesis,arc ion plating technology,which is commonly used in deposition of coating,is used to deposit the coating,and the effect of the TiAlN insertion layer is optimized by adjusting the thickness ratio of TiAlN/AlCrSiN.To solve the problem that the"large particles"of the arc ion plating coating will reduce the wear resistance of the coating,micro-blasting post-treatment experiments are carried out on the TiAlN/AlCrSiN coatings.And the changes and mechanism of the friction coefficient of the coatings after micro-sandblasting under different parameters are studied.The main research contents and results are as follows:(1)The TiAlN/AlCrSiN multilayer coatings with different thickness ratios are prepared,and the mechanical properties and the cutting failure mechanism of the coating tools are studied.The research results show that the coatings have a NaCl-type face-centered cubic structure,and the main phase is c-AlTi N/c-AlCrN solid solution phase,which grows preferentially along the(200)plane.As the ratio for thickness of TiAlN/AlCrSiN increases,the hardness of the coatings decreases,and the adhesion of the coatings increases.The failure modes of TiAlN/AlCrSiN coating tools in turning include mainly include brittle fracture and flank wear.As the ratio for thickness of TiAlN/AlCrSiN increases,the brittle fracture mechanism of coated tool gradually changes from the combined action of fatigue crack propagation and thermal crack propagation to the single fatigue crack propagation.(2)Heat treatment is carried out on the coatings,and the effect of the thickness ratio of TiAlN/AlCrSiN on the thermal stability,high-temperature oxidation resistance and hardness of the coating is studied.The research results show that the coatings can maintain high hardness after high temperature treatment even at 900?.The coatings exhibit better thermal stability and high temperature oxidation resistance when the ratio for thickness of TiAlN/AlCrSiN increases.(3)The friction properties of TiAlN/AlCrSiN coatings are studied by applying micro-sandblasting post-treatment to the coatings.The research results show that after sandblasting,the hardness of the coating increases and the friction coefficient decreases.The coating sandblasted at 0.3 MPa for 20 s shows the best surface smoothness and flatness,and the friction coefficient of the coating is the smallest.The wear mechanism of the deposited coating is mainly abrasive wear,oxidative wear and adhesive wear,while the wear mechanism of the coating after micro-sandblasting changes to adhesive wear with slight abrasive wear.