冷喷涂IN718涂层组织及性能研究

Microstructure and Properties of Cold Sprayed IN718 Coating

目的针对Ti6Al4V耐磨性能较差的问题,利用高压冷喷涂技术在Ti6Al4V基体表面以不同的工艺参数制备了IN718涂层,为在Ti6Al4V基体表面制备高性能IN718涂层提供基础理论依据。方法采用光学显微镜和扫描电子显微镜对涂层组织、断口形貌进行观察分析,以便更好地了解不同的工艺参数和工作气体类型(He/N_(2))对IN718涂层组织形貌、力学性能和摩擦磨损性能的影响。结果以N_(2)为推进气体制备的IN718涂层,其结合强度为115 MPa,硬度为557HV0.3,孔隙率约为0.24%,涂层磨损率为5.34×10^(–4) mm^(3)/(N·m);以He为推进气体制备的IN718涂层,其结合强度可高达256 MPa,是以N_(2)为推进气体制备涂层的2倍多,硬度为602HV0.3,明显高于以N_(2)为推进气体制备的涂层,涂层孔隙率和缺陷明显减少,孔隙率测试结果约为0.1%,涂层更加耐磨,磨损率为3.51×10^(–4) mm^(3)/(N·m)。结论相较于以N_(2)为推进气体制备的IN718涂层,以He为工作气体制备的IN718涂层的组织更致密、涂层孔隙率更小,硬度和结合强度更高,耐磨性能更好,所以采用He可以制备出性能更加优异的IN718涂层。

Cold spray technology is an emerging additive manufacturing technology.Its low temperature and high speed characteristics enable powder particles to be deposited on the surface of the substrate in a solid form,effectively avoiding the oxidation of the coating and the thermal stress damage to the substrate.The sediment has a compact structure and excellent mechanical properties.The work aims to prepare IN718 coating by high pressure cold spray technology on the surface of Ti6Al4V substrate with different process parameters to solve the problem of poor wear resistance of Ti6Al4V,thus providing a basic theoretical basis for the preparation of high-performance IN718 coating on the surface of Ti6Al4V substrate.100 mm×100 mm×3 mm Ti6Al4V substrate was taken as the base material and polished with sandpaper,and cleaned.Industrial IN718 powder was taken as raw material,with main components of Ni,Cr,Nb and Mo.In the cold spray process,N_(2)(5 MPa,950℃)and He(3 MPa,950℃)were used as carrier gases,the distance between the gun nozzle and the substrate was 30 mm,and the delivery rate was 100 g/min.Optical microscope(VHX-900)and field emission scanning electron microscope(GeminiSEM300)were used to observe the fracture morphology,wear morphology and cross-sectional structure of the coating.The microhardness tester(FM-700)was used to test the microhardness of the coating and the substrate,the friction and wear tester(MS-T3000)was applied to test the friction and wear,and the three-dimensional surface profiler(DEKTAK XT)was adopted to measure the wear profile and volume of the coating.Then,the friction and wear rate was calculated.The effects of different process parameters and working gas types(He/N_(2))on the microstructure,mechanical properties and friction and wear properties of IN718 coating were studied.The IN718 coating prepared with N_(2)as the propellant gas had a bonding strength of 115 MPa,a hardness of 557HV0.3,a porosity of about 0.24%,and a coating wear rate of 5.34×10^(–4)mm^(3)/(N·m).The bonding strength of the IN718 coating prepared with He as the propellant gas was as high as 256 MPa,which was more than twice that of the coating prepared with N_(2)as the propelling gas,and the hardness was 602HV0.3,which was significantly higher than that of the coating prepared with N_(2)as the propellant gas.The porosity and defects of the coating were significantly reduced,the porosity test result was about 0.1%,the coating was also more wear-resistant,and the wear rate was 3.51×10^(–4) mm^(3)/(N·m).Compared with the IN718 coating prepared with N_(2)as the propellant gas,the IN718 coating prepared with He as the working gas has denser structure,lower coating porosity,higher hardness and bonding strength and better wear resistance.Therefore,He can be used to prepare IN718 coating with better performance.Under the optimal parameters,cold spray technology can be used to prepare dense coatings with high interfacial bonding.Using He as the carrier gas to increase the deposition rate of powder particles is the main reason for improving the wear resistance of the coating.High hardness,low porosity and defects effectively reduce the occurrence of friction shedding.