Effect of glow-discharge ionized nickel-chromizing with arc source and shot peening on the fretting fatigue resistance of Ti alloy

Glow-discharge ionized nickel-chromizing with arc-source was used to treat Ti5Al2.5Sn titanium alloy. The phases and constituent distribution in the treated surface were investigated by X-ray diffraction and energy dispersive spectroscopy. Shot peening was introduced to post treat the alloyed layer in order to synergically improve the fretting fatigue resistance of titanium alloy. The results show that a composite modified surface of NiCr coating on nickel-chromium diffusion layer, which consists of N₃Ti and other phases, is formed on titanium alloy surface. Thus the hardness and wear resistance of titanium alloy are increased remarkably. As compared with the alloy subjected to shot peening alone, the titanium alloy after nickel-chromizing and shot peening shows better fretting fatigue resistance. This is determined by the synergetic effect of the high wear resistance of the alloyed surface and the residual compressive stress induced by shot peening.