Design, Preparation And Tribological Mechanism Of Ni-based Self-lubricating Composite Oxide Coatings In Wide Temperature Ranges

In order to solve the problem of wear failure and material failure in the increasingly complex service environment of mechanical parts,it is urgent to develop high wear resistant materials and improve the anti-wear and anti-friction performance of mechanical parts.Oxide ceramics have excellent high melting point,high hardness,high chemical stability and so on.Accordingly,oxide ceramic coatings prepared by thermal spraying have excellent properties of high temperature resistance and wear resistance.Based on the ionic potential and cation polarizability principal in this articles,NiAl-MoO₃?NiAl-MoO₃/BaO?NiAl-MoO₃/CuO composite coatings were prepared by atmospheric plasma spraying technique,and the effects of oxidation addition on the structure,mechanical and tribological properties of the coatings were investigated,the high temperature lubrication mechanism of the composite coatings were analyzed by XRD,TEM,SEM and Raman.The main findings are as follows:1.MoO₃ powder purchased was re-granulated by high energy ball milling,and the powder with good flowability and particle size distribution of 38?m-75?m was prepared by sintering and crushing.2.NiAl-MoO₃?NiAl-MoO₃/BaO?NiAl-MoO₃/CuO composite coatings with different oxide content were prepared by plasma spraying.The effects of oxide content and composition on the microstructure and mechanical properties of the coatings were investigated.According to comparison,we found that the NAMC?NAMB?NAM coatings were prepared with the optimum combination strength of 45Mpa>40Mpa>30Mpa.3.The results show a excellent tribological performance when the additive oxide content of all coatings is 30wt%,the NiAl-MoO₃ composite coating has excellent tribological properties at 800°C,and its coefficient of friction is 0.15,the wear rate of the coating is6.55×10^-5mm³N^-1m^-1,but the tribological properties of the coating are poor at RT-400°C,the Friction Coefficient is 0.15 at 800°C and the wear rate is 9.31×10^-5mm³N^-1m^-1.The friction coefficient of the coating further decreases at 200-400°C on the basis of the NAM coating,However,the friction coefficient of RT and the wear rate at 800°C are still relatively high,the NiAl-MoO₃/CuO composite coating prepared by optimizing compounding has good wear resistance not only at RT⁴00°C,but also at 800°C,at the same time,the coating still has excellent tribological properties at 800°C,the friction coefficient is close to 0.16,and the wear rate is 3.7×10^-5mm³N^-1m^-1.4.The results show that all the coatings are in accordance with the applicable range of oxide ion potential,and the formation of NiMoO₄,BaMoO₄ and CuMoO₄ reflect the application of ion potential difference in a certain sense.On the one hand,its lubrication mechanism is due to the unique structure of BaMoO₄ and the thermal decomposition of CuMoO₄ under high temperature,On the other hand,the excellent friction and wear properties of the composite coatings at high temperature can be attributed to the formation of Molybdate BaMoO₄,NiMoO₄,CuMoO₄ and other lubrication phases formed by the chemical reaction of the worn surface and coordinated lubrication with NiO and MoO₃,which cause the formation of continuous and smooth lubrication film on the worn surface,the friction coefficient and wear rate of the high temperature coating are reduced.