Evaluation of Metallic Parts Defects to Determine Repair Process Strategies through Laser Metal Deposition

Abstract

With technological advances, additive manufacturing processes have been gaining prominence in several industrial areas including maintenance, repair, and overhaul (MRO) processes. A process with great potential for repairing and rebuilding metal parts is laser metal deposition (LMD) technology. Despite the high potential, LMD implementation in the repair industry is not straightforward, due to the geometry variability of parts and damages to be repaired. This paper presents a repairability study that evaluates the remaining volume of the repair of different types of damages in AISI 316L parts by LMD, and determines the most appropriate deposition strategies to adapt to the repair process. This study involves the characterization and classification of common defects in metallic parts and the development of a design of experiments, in which, given the damage geometry, volume, and location, the best repair toolpath to be adopted and the ideal parameterization for the repair process are determined. The ability to correct part damage is assessed from a geometric, mechanical and energetic approach, and explores the possibility of including LMD in an adaptive and intelligent MRO system. The result of this work establishes a new deposition strategy approach based on a modified contour-parallel deposition strategy for repairing metal parts. This study also demonstrates that in surface damage cases, a fixed point strategy is highly effective, especially when using higher laser power values and larger laser spot diameters, enabling an easier process automation. However, in edge and corner damage cases, the best repair approach is using trajectory strategies that constitute material support between deposition tracks and layers. Additionally, it is demonstrated that the corners are the most critical zones that require temperature control throughout the entire repair process.