Microstructure, mechanical property, and dry-sliding behavior of sintered alloys produced from Fe-0.5Mo-0.15Mn-1.2C added with different MoS2 contents

The production of sintered self-lubricating alloys from iron (Fe) or Fe-based powders mixed with molybdenum disulfide (MoS2) usually suffers from interaction between metal powder base and MoS2, resulting in local melting and phase changes. The details of phase changes are often ignored in most previous studies. To fully understand the interrelationship between microstructures, mechanical properties and tribological properties of sintered MoS2-containing self-lubricating alloys, phase characterization, mechanical property testing, and dry-sliding testing were conducted in this work. Experimental sintered alloys were produced from pre-alloyed Fe-0.5Mo-0.15Mn powder mixed with fixed carbon content of 1.2 wt% and varied MoS2 contents (2.5 to 15.0 wt.% with 2.5 increment) by sintering at 1150 C and followed by slow cooling. The sintered MoS2-free alloy (Fe-0.5Mo-0.15Mn-1.2C) showed a typical hypoeutectoid steel microstructure comprising proeutectoid ferrite and ferrite + carbide (FC) mixture, possibly due to incomplete dissolution of added graphite at low sintering temperatures. The MoS2 additions with the contents investigated under this work led to better graphite dissolution, supported by proeutectoid ferrite disappearance and matrix coverage by FC mixture. However, due to strong interaction between metal powder matrix and MoS2, the formations of new phases, such as iron sulfide (FS) and Fe-Mo intermetallic were observed. The MoS2 addition led to changes of tensile properties and hardness. The friction coefficient values increased with increasing MoS2 content whereas specific wear rates were improved in all sintered MoS2-added alloys.