Microstructure and mechanical properties of H13 steel block produced by wire arc additive manufacturing

The H13 steel block was successfully prepared by cold metal transfer(CMT) wire-arc additive manufacturing (WAAM) method. The microstructure characteristics and mechanical properties of the printed block were both studied by experiments. It was found that there were obvious difference in the microstructure and mechanical properties between the central part and overlapping parts of the printed block. It was shown from the microstructure observation that the printed block was mainly composed of martensite and residual austenite. There was an obvious primary austenite grain boundary observed in the base phase. In addition, compared with the overlapping part, the content of residual austenite in the central part was lower. It was shown that the average value of the microhardness in the central part was 596HV, while it was 534HV for the overlapping part due to the higher content of residual austenite. Tensile tests were conducted for different direction of the printed block. Micropores with a volume of 100-400 mu m3 were observed in the printed block, with 90 % of the micropores in the range of 100-200 mu m3 in volume. The micropores were uniformly distributed in the sample. The presence of micropores leads to the low elongation and tensile strength.