Improving vacuum gas nitriding of a Ti-based alloy via surface solid phase transformation

The traditional surface nitriding technology of titanium alloy usually adopts the temperature above 700 degrees C to ensure the nitriding effect, but the high temperature will lead to the deterioration of the Matrix structure and reduce the mechanical properties. In this paper, the metastable beta phase was formed on the surface of TiZrAl alloy by laser quenching, compared with the 10 mu m thick nitrided layer mainly composed of (TiZr)N and alpha-Ti phases under the traditional process, the thickness and nitrogen content of nitrided layer were increased by the thermodynamic driving force of beta ->alpha phase transformation and the kinetic diffusion of phase interface, the effective thickness of nitrided layer was increased to 15 mu m via nitriding at 500 degrees C. the (TiZr)N and alpha-Ti phases were dominant in the surface layer, and (TiZr)N-0.3 and alpha-Ti phases were dominant in the inner layer, nitriding layer hardness up to 1200HV. In this paper, a novel nitriding technology is used to achieve excellent nitriding effect at low temperature, which has important reference significance for surface nitriding and carburizing of titanium alloys and other alloy materials.