Multiple Needle Cathodes Plasma Surface Alloying of Ti6Al4V with W-Mo-C-N

Abstract

A multiple-needle-cathode plasma surface alloying process has been developed for improving the properties of surface hardness, wear resistance and corrosion resistance of Ti6Al4V. The process is carried out at temperatures below 800 °C and facilitates the simultaneous introduction of W, Mo,nitrogen and carbon into the surfaces of Ti6Al4V forming gradient alloying layer structure with an extremely high hardness. The process is performed at working pressure of 30Pa-80Pa with 9-needle-cathode of W80Mo20 alloy rods array and a high pure graphite plate cathode as target electrode. A maximum microhardness is 4-6 times much harder than the substrate. The results show the presence of carbide and nitride ceramics phases contribute to high microhardness and wear resistance. The multiple-needle-cathode discharge plasma treatment is an effective method for improvement of the mechanical and tribological properties of titanium-base alloys by formation of graded diffusion hard surface layers. The present paper describes this novel process and properties characteristics.