High stress abrasive wear mechanism of LM13-SiC composite under varying experimental conditions
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I. INTRODUCTION
ALUMINUM alloy hard particle composites find a wide range of applications in several automobile, aerospace, and mineral processing components because of their excellent combination of high specific strength, specific modulus, improved high-temperature strength, better wear and seizure resistance, good corrosion resistance, low coefficient of thermal expansion, etc.[1–6] In recent years, enormous attention has been paid toward the weight reduction of automobiles for better fuel efficiency by the way of replacing heavier metallic components with Al or Mg alloys. In this regard, a number of Al alloy composite components such as brake drums, pistons, cylinder blocks, cylinder liners, drive shafts, crank shafts, etc. have been developed to replace cast iron components.[1] It has also been reported that Al composites are emerging as potential materials for railway brake rotors.[7] All these components are, in general, subjected to severe wear due to sliding, abrasion, and erosion and corrosion. Extensive studies have been carried out to assess the wear, seizure, and corrosion behaviour of composites as compared to the base alloy[8–20] under varying triboenvironment and triboconditions. It has been noted that the abrasive wear rate of Al-hard particle composites is less than that of the base alloy and comparable to cast iron especially at moderate applied load and finer abrasives.[10–15] The sliding wear resistance and the seizure resistance of the composite are reported to be significantly higher than those of the alloy because of the improved adhesive wear resistance and hightemperature strength of the composite.[16–20] Additionally, the hard ceramic particles act as protruded particles over the specimen surface, which reduce the contact areas between S. DAS, Scientist EII, D.P. MONDAL, Scientist ‘C,’ and S. SAWLA, Project Fellow, are with the Regional Research Laboratory (CSIR), Bhopal 462 026, India. Contact e-mail: [email protected] or [email protected] S. DIXIT, Head, Applied Chemistry, is with the Maulana Azad College of Technology, Bhopal - 462 007, India. Manuscript submitted January 18, 2002. METALLURGICAL AND MATERIALS TRANSACTIONS A
the two counter surfaces and thus result in less wear and a lower coefficient of friction and temperature rise during sliding wear.[16–20] The hard ceramic particles also help in the formation of a stable mechanically mixed layer (MML) over the composite surface even at severe wear condition.[16–20] The MML consists of fractured aspirates from both the surfaces, compacted debris generated from the counter surface and the specimen surface, and entrapped oxide particles and base material. The subsurface also undergoes severe plastic deformation leading to fracture of silicon needles and alignment of these particles and precipitates along the sliding direction. It has also been reported that MML becomes very unstable or may not be forming at all at higher applied load and greater sliding speed.[21] The abrasive wear is also similar to the sliding wear especially at lo
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