Influence of two different range of sillimanite particle reinforcement on tribological characteristics of LM30 based composites under elevated temperature conditions

Abstract

In this work, high temperature wear-resistant LM30/sillimanite composites for automotive applications have been fabricated. Dual particle size composites reinforced with naturally occurring sillimanite mineral were processed and investigated for operating temperatures in the range of 50–300 °C. Sillimanite particles with size range of 1–20 μm (fine) and 75–106 μm (coarse) were mixed in weight ratio of 3:1, 1:1, and 1:3 to be reinforced to the LM30 alloy. SEM micrographs and area mapping/line mapping profile results showed presence of different phases and revealed that sillimanite inclusion changed the morphology of proeutectic silicon to globular and refined its grain size. Particles were well distributed in LM30 matrix. Increase in reinforcement level of particles led to continuous improvement in properties. As such, the best properties were obtained in composite containing 15 wt% sillimanite with proportion of fine: coarse particles as 3:1 (15-DPS3 composite). The transition temperature of wear mode increased from 150 °C for base alloy to 200 °C for composites. For the temperature-pressure condition of 200–1 MPa, 15-DPS3 composite showed 15% higher hardness, 80% lower wear rate, 48% lower friction coefficient, and 28% lower thermal expansion coefficient than base alloy. These wear characteristics of composites were comparable to the commercially used grey cast iron material. XRD of wear track/debris confirmed the formation of tribolayer. SEM analysis of wear track/debris identified the wear mechanisms causing materials loss under different contact pressures. Light-weight and economical composites developed in this research can act as a good substitute for the heavy cast iron components used in industry.