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Experimental Investigation of Residual Stress Relief Using Pre- and Post-clad Heating in the Laser Cladding Process
H. Hu, A. Iqbal, X-L. Wang and H-C. Zhang

Laser cladding is a coating technology with many advantages as compared to conventional techniques like plasma welding, overlay welding, and thermal spraying, etc. It is meant to deposit a new layer of desired material on the surface of a base material with very low heat input to form coatings which are metallurgical sound and dense. Susceptibility of cracking of coatings is mainly determined by the stresses developing during the solidification of molten coatings and substrate. Residual stress of the deposited layer is crucial to the operating life span and safety of the remanufactured, repaired, or fabricated components by laser cladding. In this work, AISI316L stainless steel powders were cladded on AISI321 stainless steel substrate using laser cladding technique. Pre- and post-clad heat treatments, using laser beam, were applied on the substrate and individual tracks, respectively. The effects of lead time (time interval between pre-clad heat treatment and cladding) and delay time (time interval between cladding and post-clad heat treatment) on the residual stress of coatings surface were investigated. It was found that the effects of lead time for pre-clad heating and delay time for post-clad heating on residual stress are significant and there exist specific values of lead time and delay time for which residual stress of coatings surface is minimal.

Keywords: Nd:YAG laser, laser cladding, stainless steel, AISI321, AISI316L, heat treatment, residual stress

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