Comparison on Dry Sliding Tribological Behavior Between β-Solidifying γ-TiAl Alloy and 40CrMo Steel

The beta-solidifying gamma-TiAl alloys have higher strength and service temperatures than conventional gamma-TiAl alloys, but currently there is still a lack of systematic and in-depth understanding of the tribological properties and wear mechanisms of this type of alloy. In this study, the dry-sliding tribological behavior of a beta-solidifying gamma-TiAl alloy with the chemical composition of Ti-44Al-3Mn-0.4Mo-0.4W (at%, named as TMMW) was investigated. For comparative purposes, the tribological behavior of a common 40CrMo steel was also examined under the same conditions. It is found that there is a significant difference in the friction coefficient values between TMMW and 40CrMo, and they exhibit different patterns as the load changes. The friction coefficient of TMMW alloy first increases and then remains relatively stable, while that of 40CrMo steel increases continuously with the increase of load. The wear resistance of the TMMW alloy is superior to that of the 40CrMo steel as the load increases from 2 N to 10 N, and the wear rate decreases from 6.97x10-3 mm3/(N<middle dot>m) to 1.88x10-4 mm3/(N<middle dot>m) under the load of 10 N. The wear mechanisms of TMMW alloy are mainly abrasive wear, accompanied by some adhesive wear and plastic deformation caused by abrasive wear, while that of 40CrMo steel is mainly adhesive wear, accompanied by certain abrasive wear and oxidation wear. It is observed that these phases are followed by beta o , alpha 2 and gamma in decreasing order of hardness. Therefore, the wear resistance of the beta o phase may be superior to that of alpha 2 and gamma phases under the present conditions. Meanwhile, the presence of beta o phase makes the alloy prone to plastic deformation during grinding, thereby maintaining a relatively stable friction coefficient value even under a high load of 5-10 N.