Preparation Of TiAlCrN Coatings By Multiarc Ion Plating And The Tribological Properties Under High Temperatures

TiAlCrN coatings are widely used in the surface protection of cutting tools and molds because of its high hardness,wear resistance,oxidation resistance and corrosion resistance.Herein TiAlCrN coatings were prepared by multi-arc ion plating technology.The prepara-tion process optimization and high temperature tribological properties of TiAlCrN coating were studied.Furthermore,this study puts forward suggestions for the preparation of TiAlCrN coating with excellent performances,which lays a certain foundation for the ap-plication of the TiAlCrN coatings under harsh high-temperature conditions,such as varia-ble temperature,high load and long-time rubbing conditions.The research contents and results of this paper mainly included the following aspects:(1)By studying the influence of substrate placement position and placement mode on the large particles on the TiAlCrN coating surface,it was concluded that the large particles on the TiAlCrN coating surface were the least when the substrates were placed flat on the upper layer of the sample holder.In addition,through the study of orthogonal experiment and taking the wear rate at 400?as the index(the lower the better),the best deposition process parameters were as follows:Ti Al target current was 90 A,Cr target current was105 A,N₂ flow rate was 160 sccm and deposition temperature was 350?.(2)The TiAlCrN coatings were successfully prepared by using the optimized deposi-tion process parameters.The TiAlCrN coatings were mainly composed of fcc-(Ti,Al)N,fcc-(Cr,Al)N and fcc-(Ti,Al,Cr)N phases.A small amount of oxide was detected on the coating surface by XPS.There were many large particles on the TiAlCrN coatings surface,most of which were 1?2?m in diameter.The thickness of the coating was about 5.2?m.The contents of Ti?Al?Cr and N in the coating were 12.57%,22.10%,19.63%and 45.70%respectively.The average hardness of the TiAlCrN coatings was 1795 HV and the second critical load of scratch test was 26.2 N.(3)The TiAlCrN coating had excellent wear resistance at room temperature.Between100?and 300?,whether at constant temperature or variable temperature,the TiAlCrN coating will be damaged due to the physically adsorbed water molecular film,resulting in abnormal friction and serious wear of dual materials.When the temperature was higher than 300?,the friction coefficient decreased with the increased of temperature,and the TiAlCrN coating was worn through at 600?.The TiAlCrN coating can maintain excel-lent friction and wear properties during cooling friction and cyclic temperature rise and fall friction.In addition,a protective oxide layer will be formed on the surface of the TiAlCrN coating during the cooling process,which can effectively reduce the wear of the coating and the wear of the processed materials.(4)At 500?high temperature:(1)the load was elastic contact between 1 and 5 N.with the increased of load,the friction coefficient of the coating decreases gradually,and the wear rate of the coating decreased first and then increased,lowest wear rate at 3N.Under low load,the TiAlCrN coating mainly produces plastic deformation,medium load mainly produces abrasive wear,oxidative wear and adhesive wear,and high load mainly produces abrasive wear and oxidative wear.(2)With the increase of friction frequency,the friction coefficient of the TiAlCrN coating increased gradually,and the wear rate increased first and then decreased,among which the wear rate at 3 Hz was the highest.Only slight wear of the coating occurs at low speed,plastic deformation and oxidative wear mainly occur at medium speed,abrasive wear,oxidative wear and adhesive wear mainly occur at high speed,and high-speed friction was conducive to the formation of protective adhesive layer.(3)With the increasd of friction time,the wear rate of the TiAlCrN coating in-creased first and then decreased.The friction in the first 15 minutes was in the running in stage,and between 15 minutes and 30 minutes was in the stable wear stage.The wear rate decreases,and the wear volume increases slowly and steadily.In the stable wear stage,the main wear modes were abrasive wear,adhesive wear and plastic deformation.