Influence of Heat Treatment on Microstructure and Tribological Behavior of Conventional Maraging Steel W720 WMR

This study evaluates the effect of different precipitation-hardening regimes on the microstructure, hardness, and tribological behaviour of W720 maraging steel. Experimental specimens were aged at temperatures ranging from 460 to 490 °C for 3–16 h following solution annealing. Tribological tests were performed using the Ball-on-Flat method under dry sliding conditions against a G40 steel ball. The worn surfaces were analysed using LSCM, SEM, and EDS. Aging increased the hardness from 323 HV1 to 580–606 HV1 and reduced the coefficient of friction from approximately 0.75 to 0.63–0.71. The lowest nominal specimen wear volume was measured for the as-received, solution-annealed W720 condition (0.011 mm3), followed by HT490_6 (0.012 mm3); these values were compared descriptively without inferential statistical testing. However, the reference specimen produced a narrow, locally deepest wear track and caused the highest wear of the counter-body. The highest wear volume of the specimen was recorded for HT480_3 (0.027 mm3), while HT460_8x2 combined the highest hardness and the lowest coefficient of friction with a high wear volume. The dominant wear mechanism was a combination of abrasive grooving, adhesive damage, and tribo-oxidation. The results demonstrated that the tribological resistance of W720 is not governed by hardness alone, but rather by the interplay between microstructure, wear-track geometry, wear-product morphology, and the distribution of wear between the specimen and the counter-body.