The influence of porosity and particles content on dry sliding wear of cast in situ Al(Ti)-Al2O3(TiO2) composite

Cast in situ particle-reinforced aluminum-based composite is characterized by in situ generation of dispersoid particles and also, further value addition due to matrix strengthening caused by alloying. These lightweight composites result in reduced weight when employed in dynamic components, leading thereby to significant fuel economy. Dry sliding behavior of cast in situ Al (Ti)-Al2O3(TiO2) composites synthesized by dispersing titanium dioxide (TiO2) particles in molten aluminum, has been investigated to explore its potential application in sliding components. Wear tests have been conducted at normal loads of 9.8, 14.7, 19.6, 24.5, 29.4, 34.3 and 39.2 N and a constant sliding speed of 1.05 m/s using a pin-on-disc wear testing machine, under dry sliding conditions. For some specimens of cast in situ composite, wear tests have been also conducted at four different sliding speeds of 0.52, 1.05, 1.57 and 2.10 m/s but at a constant normal load of 34.3 N. The results show that the cumulative volume loss and wear rate of cast in situ composites are significantly lower than those observed in either the cast commercial aluminum or cast unreinforced Al-Ti base alloys, under similar load and sliding conditions. At a given particle content, the wear rate increases with increasing porosity content due to its effect on both the real area of contact and subsurface cracking. The wear rate of cast in situ composites with relatively lower porosity content, decreases with increasing particle content but, in presence of relatively large porosity content, the wear rate decreases only by a little or remain unchanged with increasing particle content. The coefficient of friction of cast in situ composite decreases with increasing porosity content but increases slightly with increasing particle content. In cast in situ composites, porosities were observed to increase the cumulative volume loss and wear rate in all the different types of cast in situ composites. Sometimes, the contributions of the reinforcing particles in enhancing the wear resistance have been obliterated by increased porosity content and therefore, it should be controlled in cast in situ composites. However, a limited amount of porosity could be tolerated in cast in situ composites without impairing its wear resistance significantly. The limitation of wear coefficient as a basis for defining wear resistance has been highlighted and wear rate has been judged as a better parameter for comparing the wear resistance of different cast in situ composites.