Toward homogeneous microstructure and mechanical properties in WAAM-fabricated H13 tool steel: effect of interpass and tempering temperatures

Wire Arc Additive Manufacturing (WAAM) is gaining traction as a viable method for fabricating large and complex shape metal components due to its cost-effectiveness and efficiency. This study investigates the influence of interpass temperature on the microstructure and mechanical properties of WAAM-fabricated H13 tool steel. A 80 × 60 × 15 mm³ wall was fabricated using the Cold Metal Transfer (CMT) welding technique. The interpass temperature was varied throughout the process to document its effects on the deposited material properties. The interpass temperature, initially set to 200 °C for the first deposition layer, was incrementally increased to 340 °C for the final layer with increments of 10 °C per layer. Optical microscopy, X-ray diffraction, and microhardness characterization were employed to document the heterogeneous nature of the multilayer, multipass material. Maintaining interpass temperatures above the martensite start temperature (approximately 280–300 °C) significantly enhances microstructural homogeneity and improves the uniformity of hardness measurements. In light of the obtained results, the possibility of eliminating the need for conventional post-heat treatment processes after WAAM is discussed as a potential approach for producing and repairing large-scale industrial components.