A pin-on-disc study of the tribology characteristics of sintered versus standard steel gear materials

Though powder metallurgy (PM) allows manufacturing of complex components, including gears, we lack knowledge of the tribological performance of PM versus standard steel gear materials. Using a pin-on-disc machine, we simulate the sliding part of gear tooth contact in boundary and mixed lubricated regions, comparing the tribological characteristics of two sintered gear materials with those of a standard gear material. The comparison considered damage mechanisms, wear, and friction between these materials in different configurations (i.e., standard versus standard, sintered versus sintered, and sintered versus standard). The results indicate that, for pairings of the same gear materials, i.e., RS-RS (16MnCr5), AQ-AQ (Distaloy AQ+0.2% C), and Mo-Mo (Astaloy 85Mo+0.2% C), RS has a lower friction coefficient. For PM and RS combinations, both PM pins have lower friction coefficients with RS disc material than do RS pins with PM disc materials. For the wear coefficient, at low and high speeds, RS pins always display better wear resistance than do AQ or Mo pins because of their high hardness and compacted microstructure. For RS-PM combinations, Mo pins display higher wear resistance than do AQ pins because their larger and more numerous pores enable good lubrication. Pins in the Mo-RS combination displayed the highest wear resistance, mainly because the pores in Mo discs hold lubricant, lubricating the contact surface and preventing adhesive wear. For the RS pin in the Mo-RS combination and the AQ pin in RS-AQ, the damage mechanism is slight adhesive wear and scuffing. For pins in the PM-PM, RS-PM, AQ-RS, and RS-RS combinations, the damage mechanism is a heavier scuffing-type adhesive wear.