Effects of tool path in remanufacturing cylindrical components by laser metal deposition

Laser metal deposition as an additive manufacturing process has been widely utilized for component repair. In this study, in order to investigate the influence of tool path on characteristics of coatings for cylindrical part repair, multi-layer cobalt-based alloy was coated on cylindrical tool steel substrates using the blown powder laser metal deposition process following the helix (H), circle-line-circle (CLC), and line-arc-line (LAL) routes. A series of analysis was performed on the coatings including shape's profile, powder-catch efficiency, microstructure, EDS, XRD, and Vickers hardness. The result shows coatings fabricated using the H and CLC routes have consistent thickness while more material was deposited near the middle for the LAL route. Powder-catch efficiency for the CLC and LAL paths was up to 28% while it was only 14% for the H route. The microstructure near the coating's starting point was columnar dendrites growing parallel to the heat flux direction. Cooling speed reduced after several layers' coating and equiaxed-like morphology appeared. Much gas porosity was discovered near the interface for LAL-coated samples. EDS and XRD analysis show Fe was diffused into the coatings. Microhardness measurement reveals that the hardness of LAL fabricated samples was slightly higher than the hardness of H and CLC samples. The result shows that the CLC path is more suitable for repairing/coating cylindrical components due to a relatively consistent shape, a high powder-catch efficiency, and defect-free deposits.