Experimental and Numerical Study of Heat Conditions during Diode Laser Gas Nitriding of Titanium Alloy

Abstract

The heat conditions of laser gas nitriding (LGN) of titanium alloy Ti6Al4V by high power diode laser (HPDL) were investigated experimentally by non-contact pyrometric measurements and infrared camera analysis. Additionally direct observations of the weld pool shape were conducted by means of high speed digital camera. In the numerical study of the laser surface processing of titanium plate 3D model of heat flow was examined. Results of temperature values, distribution and temperature isotherms obtained from the 3D model were next applied in the two-dimensional stationary model of liquid metal flow in the weld pool. Experimental and numerical study showed that the temperatures of the weld pool during laser gas nitriding of the titanium alloy are significantly higher compared to these determined during laser melting in argon atmosphere at the same heat input. Additionally severe turbulences of liquid metal in the weld poll (Marangoni convection) were found during both experimental and numerical analysis.