Two-dimensional, transient model for mass transport in laser surface alloying

Abstract

The process of alloy generation during laser surface alloying was examined. A numerical model was developed that solved the two-dimensional, transient equation for convection diffusion of matter in the melt pool using the alternate-diagonal implicit method. Velocity distributions used were for steels for a laser power of 1.5 kW, a 0.001-m beam diameter and a traverse speed of 0.01 m/s. Calculations were made for a uniform surface mass flux of 5 and 10 kg m2 s−1 and values of 100 and 1000 for the Peclet number for diffusion. The results showed that powder particles injected into the melt pool melted practically instantaneously, that good mixing was determined by the pattern of fluid flow, that average solute contents increased linearly with increasing interaction time, and that a change in the solute diffusivity by a factor of 10 did not greatly alter the predicted solute distribution. Good mixing was also found with surface flux over only a part of the melt pool. The conclusions were that fluid flow dominates the process of mass transport and determines the nature of the solute distribution, that powder feed is an effective method for surface alloying, and that results of the model could be used to better understand the process of laser surface alloying.