Evaluation of gas nitrocarburizing effects on impact-sliding wear behaviour of AISI H13 die steel

To simulate the combined impact and sliding forces encountered during the extrusion process, a novel inclined ball-on-plate impact-sliding test was developed to evaluate the wear behavior of the nitrocarburized surface layer on hardened H13 (QT) steel. The treated steels were structurally characterized using a light optical microscope (LOM), accompanied by hardness evaluations. Gas nitrocarburizing notably improved the surface properties of QT steel, increasing surface hardness from 406 HV0.05 to 881 HV0.05. The treated layer consisted of an 8.9 µm white layer and a 110 µm diffusion zone. Wear tracks formed after impact-sliding wear tests were analyzed under the LOM and SEM to identify the underlying wear mechanisms. For the QT steel, severe plastic deformation and material transfer from the counter-body (AISI 52100 ball) contributed to the development of three-body abrasive wear. As a result, the wear rates of the nitrocarburized H13 steel (QT+NC) were reduced by 89% in the impact region, 20% in the sliding region, and 35% overall compared to the QT steel, a performance attributed to the presence of a protective oxide layer on the continuous white layer.