No abstract

Surface nitriding of pure Ti and Ti-6Al-4V alloy was performed in potassium nitrate molten salt bath at temperatures ranging from 600 to 700uC for 2-18 h. The formation of a compound nitride layer comprising of e-Ti 2 N and d-TiN phases was identified with thicknesses of 1-12 mm for pure Ti and 1-6 mm for Ti-6Al-4V respectively. Ti-6Al-4V was found to develop an oxide phase upon nitriding for .8 h at 700uC. Maximum hardness values of 1470 HV for pure Ti and 1367 HV for Ti-6Al-4V were achieved. Under identical treatment conditions, the pure Ti sample was found to produce a thicker nitride layer than that of Ti-6Al-4V, proving that the presence of alloying elements hinders the growth of the nitride layer. Our study concludes that the present salt bath nitriding technique can produce a comparatively thick case depth with reasonably high hardness at relatively low temperature.