Mechanism of Titanium Matrix Composite Ti/TiN Formation during Diode Laser Gas Nitriding of Ti6Al4V

Abstract

Three mechanisms of titanium matrix composite Ti/TiN formation during diode laser nitriding of Ti6Al4V alloy in liquid stage were identified and discussed. When the titanium alloy surface is melted by a laser beam the first mechanism of nucleation and growth of d-TiN was identified in the temperature range of melt pool from 1650 up to 2320 °C, when the nitrogen concentration in the Tia solution reaches at least to the concentration limit in a range 20,5 to 22 at. %. Next different mechanism of nucleation of d-TiN was identified in the temperature range of melt pool from 2320 up to 2950 °C. In turn, the third mechanism of d-TiN formation was identified above the melting point of titanium nitrides, i.e. 2950 °C.