The influence mechanism of primary carbides on the tribological behavior of M50 steel

Primary carbides in high-carbon alloyed steels have sparked considerable debate over their impact on wear resistance. Due to concomitant alterations in matrix microstructures, it's difficult to isolate the individual effects of primary carbides. This study prepares M50 steel without primary carbides via powder metallurgy process (PM-M50), and ensures that its matrix structure remains consistent with that of M50 steel prepared by casting and forging processes (CF-M50) via applying the same heat treatment procedure. A comprehensive examination of microstructural, mechanical, and tribological behavior was conducted. Notably, CF-M50 contained primary carbides up to 10 μm in size, arranged in distinct banded clusters, while PM-M50 effectively mitigated such carbides and instead exhibited a homogeneous distribution of fine, near-spherical carbides. Consequently, PM-M50 showed enhanced properties: compared with CF-M50, its impact toughness increased by 27 % and wear volume decreased by 59 %. The main wear mode of CF-M50 involved abrasive wear and peeling pits, which arose from the fracture and dislodgment of large primary carbides. These findings underscore the detrimental effect of primary carbides on wear resistance, highlighting the removal of primary carbides as a pivotal consideration for future research.