Effect of grain size on friction and wear behavior of Ti 3SiC 2

Abstract

The effects of grain size on the sliding friction, sliding wear, and two-body abrasive wear behavior of Ti 3SiC 2 were investigated. Samples with two different grain sizes, namely, 5 μm (`fine') and 100 μm (`coarse'), were used as discs in pin-on-disc sliding wear tests against a 440C steel pin and as rectangular pins in diamond belt abrasion tests. In the pin-on-disc test, irrespective of the grain size, it was found that the material undergoes an initial transition stage where the friction coefficient, μ, increases linearly to 0.15 to 0.45. After this transition stage, μ rises to steady state values, of about 0.83 for both coarse- and the fine-grained materials. It was concluded that the transition from the low to high μ is due to accumulation of debris entrapped between the disc and the pin, resulting in third-body abrasion. The average sliding wear rates in the pin-on-disc tests were 4.25×10 −3 and 1.34×10 −3 mm 3/N m for the fine and the coarse grains, respectively. In the diamond belt abrasion tests, the average wear rates were much higher: 6.14×10 −2 and 3.96×10 −2 mm 3/N m for the fine and the coarse grains, respectively. In the fine-grained material, it was concluded that the wear mechanisms include grain pre-fracture and removal. Delamination, crack bridging, grain deformation, microcracking, and grain fracture are the operative wear mechanisms observed in the case of the coarse-grained material. It is this multitude of possible sliding energy dissipation mechanisms that is believed to enhance the wear resistance of the coarse-grained material relative to the fine-grained one.