Aluminum based metal matrix composites against molybdenum alloy coated cast iron in reciprocating wear

In pursuit of a light weight and high efficiency engine, a metal matrix composite (MMC) is one of the best candidates for a material to replace the conventional cast iron for the cylinder liner material. The reinforcement particle size, volume fraction and matrix material of the MMC affect the wear performance of the cylinder block liner. Prior to the present research, little was known about how to optimize performance and why. In the present research, two classes of MMCs were examined as liner materials. One is 10% 3, 9, 15 {dollar}mu{dollar}m SiC{dollar}rmsb{lcub}p{rcub}{dollar}-9.5Si Al MMC as well as 20% 15 {dollar}mu{dollar}m, SiC{dollar}rmsb{lcub}p{rcub}{dollar} and the other is 10% 0.3 and 1.3 {dollar}mu{dollar}m TiB{dollar}sb2{dollar}-high purity 2024 Al MMC. The mating ring material is commercially available Mo alloy-coated cast iron. A newly designed reciprocating sliding wear apparatus was used to simulate the piston-ring/cylinder-liner contacts in an engine.; After one hour of wear testing, the trend is that, at the same reinforcement volume fraction for each mating group SiC{dollar}rmsb{lcub}p{rcub}{dollar}-9.5Si Al MMC mating with Mo alloy-coated cast iron and TiB{dollar}sb2{dollar}-2024 Al MMC mating with the same ring material, the weight loss of both the liner and ring are smaller if the reinforcement particle size is smaller. A similar trend was found for the volume fraction effect: smaller reinforcement volume fraction gave smaller weight loss at the same reinforcement particle size. The best system wear performance in the present research was with 10% 3 {dollar}mu{dollar}m SiC{dollar}rmsb{lcub}p{rcub}{dollar}-9.5Si Al MMC mated against the Mo alloy-coated ring.; The wear mechanisms of MMC and Mo alloy-coated cast iron mating system were found. Mo wear particles cut the mating MMC matrix, and this is the main reason of weight loss of the MMCs. On the other hand, the weight loss of the ring material is mainly due to contact fatigue. SiC plays two major roles in the wear mechanism. One is wear of the ring material (creating Mo wear particles by contact fatigue), and the other is protecting the MMC from being grooved by Mo wear particles. These two contradictory roles of SiC particles create a trade-off relationship for choosing the optimum reinforcement particle size and volume fraction. The wear failure modes of MMCs are also discussed.; Wear debris analysis of "after-test" oil aids in illuminating the wear mechanisms. Some spherical oil additive particles previously unreported were found in the fresh 10W30 engine oil. They may play a role like ball bearings in the wear system. The major function of the oil additive particles in the wear system is still not clear. Some discussions about these oil particles are included.