Influence of process strategy on distortion and residual stresses for the powder based laser metal deposition process

Laser metal deposition (LMD) induces a complex 3-axis residual stress state, which superimposes the external service stresses and can cause unpredicted in-service failures. To optimize the process it is important to know the mechanisms and the opportunities to influence the occurrence of residual stresses. From the mathematical point of view, laser metal deposition represents a free boundary value problem. The track geometry is part of the solution. Previously the authors developed a thermal model that is used to calculate the time- and space resolved temperature distribution and the track geometry. The thermal model encompasses the powder stream, its interaction with the laser radiation, the shadowing of the laser radiation by the particles, the heating of the particles and the melt pool computation. In this publication, the evolution of residual stresses for overlapping tracks for single and multilayer processing for different powder mass rates is described.