Reactive gas shielding during laser surface alloying for production of hard coatings

The effects of nitrogen addition to shielding gas during laser surface alloying with a mixture of 80 wt.% 431-type stainless steel and 20 wt.% titanium carbide powders were investigated. Microstructural characterization of the laser deposits indicated that titanium carbide melted and re-precipitated as fine carbides from the liquid melt during cooling. With 100% nitrogen shielding and the same powder mixtures, a deposition with increased hardness was obtained. The microstructural evolution in the deposit was calculated with equilibrium thermodynamic calculations.