The Laser Aided Manufacturing Process (LAMP) lab at the University of Missouri – Rolla is currently developing a laser-based part repair system especially for steel die/molds.  This hybrid machining-laser deposition repair process eliminates the limitations of typical welding repair process such as big Heat Affect Zone (HAZ), shape deformation etc.  In addition, the bonding strength and other mechanical properties of the repaired part using hybrid repair process are better than the process using welding repair process.  This process has successfully repaired a worn out die core.

LAMP is currently working to characterize laser deposited material compared to the TIG welding process.  Samples were created by sectioning a H13 tool steel bar into 18mm cubes with a wire EDM. These cubes were separated into two groups.  One group was TIG welded, the other laser deposited, both to a total height of 36mm.  This paper contains testing results from both sample groups, as well as the base H13 bar.  Tensile tests and hardness tests were performed.  A fracture analysis and microstructure comparisons were conducted on the samples after mechanical testing.

Due to a faster cooling rate, the hardness of deposited samples is higher than that of welded samples.  The fracture surface analysis shows that the deposited samples retain some ductility, indicating that the hardness can be improved via heat treatment.  In welded samples, the hardness of a section with equiaxed microstructure is lower than that of the section whose microstructure is dendritic. Also, the TIG welded samples exhibited a very low ductility.