Effect of heat treatment on the microstructure and wear behavior of AISI H13 hot work tool steel produced via laser powder bed fusion

The laser powder bed fusion (LPBF) process can produce H13 steel with a relative density exceeding 99.9 % by preheating the substrate. The mechanical properties of the alloy can be further enhanced through heat treatment (HT). This work investigated the microstructure and wear behavior of LPBF-processed H13 steel preheated at 500 °C (PT500H13) after HT. The sample tempered at 500 °C for 8 h (H13-500/8h) exhibited a hardness of 678.95 ± 11.14 HV1.0, and the cellular structure was still retained. After tempering at 550 °C for 4 h (H13-550/4h), the hardness increased to 664.77 ± 13.06 HV1.0, with a dissolved cellular structure. The wear resistance of H13-550/4h was superior to that of H13-500/8h, and both materials significantly outperformed conventionally manufactured H13 steel (CM-H13). Under a low applied load, the H13-550/4h and H13-500/8h steels were more prone to oxidation than CM-H13 was, leading to the formation of a tribo-oxide layer (TOL) that reduced the coefficient of friction (COF) and wear rate. H13-500/8h entered the oxidative wear stage earlier than H13-550/4h did, probably because of the high number of fine carbides. Compared with that in H13-550/4h, the cellular structure in H13-500/8h effectively hindered crack propagation into the substrate, resulting in a lower degree of delamination wear. The primary wear mechanisms for H13-500/8h were oxidative wear and abrasive wear, whereas material loss for H13-550/4h was attributed mainly to oxidative wear and delamination wear. The wear mechanism of CM-H13 transitioned from delamination wear under a low applied load to delamination wear, oxidative wear, and abrasive wear under a high applied load.