Process parameter optimization for directed laser deposition of hot work tool steel Dievar

Abstract Tool steel utilized in hot work applications are prone to costly and time-consuming maintenance repair due to wear generated on the tool surface from static and dynamic high temperature loading during the production processes. Traditionally, the repair is mainly done by subtractive machining of the tool profile. Implementation of an additive manufacturing technology such as directed laser deposition can greatly reduce maintenance time by targeting specifically the worn areas of the tool surface. In the presented work, a commercially available hybrid additive manufacturing and computer numerical control system is used to deposit a powdered hot work tool steel called Dievar. The central composite design is used in the experimental setup to optimize the most influential input parameters; powder feed rate, traverse speed, and laser power by analyzing single track geometry. The presented process window produced defect free parts without the need for preheating, Applying a powder feed rate of 6.5 g/min, traverse speed of 550 mm/min, and laser power of 1500 W, yielding an average as-built hardness of 610 HV 0.5 while retaining the required pre-hardened properties in the heat-affected zone in the substrate, with a minor hardness reduction of 4–5% post-deposition. Additionally, the research revealed that the established boundary conditions for aspect ratio and dilution is not an absolute requirement to achieve a fully dense part without lack of fusion or cracks. Engineers working in the field of additive manufacturing may use the presented method to find optimal process parameters and qualify the implementation of directed laser deposition in their industry, avoiding a unnecessarily large selection of samples for testing and thus saving time and resources.