Laser Surface Cladding For Structural Repair

Laser cladding is a powder deposition technique, which is used to deposit layers of clad material on a substrate to improve its surface properties. It has widespread application in the repair of dies and molds used in the automobile industry. These molds and dies are subjected to cyclic thermo-mechanical loading and therefore undergo localized damage and wear. The final clad quality and integrity is influenced by various physical phenomena, namely, melt pool morphology, microstructure evolution, and residual stress generation. Consequently, it is imperative to understand the physical phenomena influencing the process variables and develop a knowledge base for the usage of this process in repair-based applications. This work aims at developing a knowledge base for the estimation of clad geometry and characteristics. In this regard, the influence of thermo-viscous effects on the melt pool for calculation of clad geometry via. Tanner’s law is investigated.
Apart from the clad characteristics, the most important aspect in laser cladding pertaining to repair is the microstructural transformation and their relation to residual stress. According, a part of this study is dedicated to understanding the complex interrelation between thermomechanical and metallurgical transformations. The individual competing physical phenomena viz. thermal, mechanical and metallurgical, are integrated to develop a coupled 3D Metallo-thermomechanical model of laser cladding. The coupled model predicts the residual stresses due to the differential thermal expansion-contraction between the clad and substrate layers as well as the strains developed due to metallurgical phase transformations. The model can predict clad geometry, dilution, HAZ and residual stress with reasonable accuracy with prediction errors lying within ~13% for most of the cases. Moreover, this study defines a simplistic approach to identify a critical height of deposition and develop process maps to identify optimal process parameters for laser cladding pertaining to repair/remanufacturing.