Simulation of laser cladding

Abstract
Nickel and titanium aluminides already show a high potential for use in lightweight applications at elevated temperatures; however, the strength of these intermetallics can be increased by directional solidification. These materials show a brittle behaviour at temperatures less than 600°C. Strength and ductility of aluminides are controlled by phase formation during solidification. The problem of crack formation had to be solved for laser rapid prototyping of intermetallics, and the process conditions for formation of directionally solidified structures have to be specified in order to generate directionally solidified TiAl parts properly. A model was developed to determine the influence of the process parameters on melt pool geometry, solidification time, and the formed structure. Temperature gradients and cooling rates were calculated using a simulation that also included feedstock material injection rate and process parameters. The experimental results were analysed using these simulations, and the process parameters were optimised so that crack-free laser-generated TiAl parts exhibiting a partially directionally solidified structure could be produced. The comparison of the simulated and experimental results led to process guidelines for laser generation of directionally solidified TiAl components.