Study Of The Preparation And Performance Of Zr-alloyed Layers And Mo-alloyed Layers On Tini Alloy Surface

Because of its good shape memory effect, super elasticity, excellent biocompatibility and good anti cavitation performance, Titanium nickel alloy was widely used in aerospace, machinery, electronics, chemical industry, energy, construction, civil and medical fields. However, due to the low hardness, poor wear and corrosion resistance and Ni ion toxicity, its applications in the human environment and other severe application environment such as cavitation were limited. The surface modification technology was the effective methods to improve its performance. Zr alloyed layers and Mo alloyed layers were prepared on the surface of TiNi alloy by the double glow plasma alloying technique. The plasma surface alloying process was optimized by analyzing the effects of the processing temperature on the formation of Zr alloyed layers and Mo alloyed layers. The surface and cross-section morphology, composition distribution and phase structure of the Zr alloyed layers and the Mo alloyed layers were analyzed. The wear properties of the Zr alloyed layers and the Mo alloyed layers in dry friction and Hank’s solution were studied. The corrosion resistance of the Zr alloyed layers and the Mo alloyed layers in the static and cavitation conditions were studied. The main research results are as follows:(1) The fine, compact Zr alloy layers and Mo alloy layers could be fabricated on surface of TiNi alloy by double glow plasma a lloying technique. The process parameters were optimized, which were temperature 950 °C, pressure 35 Pa, alloying time 2 h, voltage difference 250 V. Both Zr alloyed layers and Mo alloyed layers were composed of two layers structure. From the surface to the matrix, there were deposited layer and diffusion layer of infiltration metal. Along the thickness direction, The element content of both Zr and Mo displayed gradient distributions.(2) Compared with the matrix, the surface hardness of the Zr alloyed layers and the Mo alloyed layers were improved significantly. The scratch test showed that there was a good bonding strength between the alloyed layer and the substrate. The biocompatibility of Zr alloyed layers and Mo alloyed layers were improved significantly.(3) The wear mechanisms of Mo alloyed samples, Zr alloyed samples and TiNi alloy matrix were abrasive wear and adhesive wear both in dry friction condition and Hank’s solution. By comparison, it could be found that the matrix had a serious adhesive wear, and the adhes ive wear of Zr alloyed sample was the second, and the Mo alloyed sample had only slight adhes ive wear and scratch. The surface resistance of adhesive wear of Mo alloyed samples and Zr alloyed samples were effectively improve.(4) Comparing the open circuit potential and the polarization curves of Mo alloyed samples, Zr alloyed samples and TiNi alloy matrix both in static and cavitation conditions, we can conclude that the corrosion resistance of Zr alloyed samples in the static and cavitation condition were better than Mo alloyed samples.