Influence of Nd(NO3)3 additive on the microhardness and wear resistance of PEO coating for TC4 matrix
To solve the problem of weak wear resistance of TC 4 alloy,silicate ceramic coating was introduced on the surface of TC4 alloy by plasma electrolytic oxidation technology.Rare earth salt Nd(NO3)3 was doped in the electrolyte of Na2 SiO3-NaOH system and the influence of the doping amount of Nd(NO3)3 on the properties of TC4 surface modified coating.The phase composition,microstructure,surface roughness,microhardness,and friction coefficient were investigated.The results showed that the surface of PEO coating was relatively complete when Nd(NO3)3 is not doped or slightly doped.When the doping amount of Nd(NO3)3 in the electrolyte exceeded 4.5 g/L,corrosion pits began to appear on the surface of the PEO coating.The PEO ceramic coating phase composition of all samples was similar,which was mainly composed of anatase type A-TiO2 and rutile type R-TiO2.Compared with the undoped Nd(NO3)3 sample,increasing the doping amount of Nd(NO3)3 led to slightly enhanced diffraction peaks of anatase phase TiO2 and rutile phase TiO2 in the coating,which indicated that Nd3+ could promote the production of anatase phase TiO2 and rutile phase TiO2 in the coating.When the doping amount of Nd(NO3)3 in the electrolyte was 3.0 g/L,the coating roughness was the minimum and the microhardness reached the maximum.The friction coefficient curve of the PEO coating was relatively straight and the friction coefficient was in the range of 0.8～0.9.When the doping Nd(NO3)3was higher than 3 g/L,the initial friction was in an unstable state.
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