Effect of vacuum infiltration boehmite gel on tribological behavior of friction materials

This study is to investigate the effect of vacuum infiltration boehmite gel on tribological behavior of friction materials. Experimental results indicate that open porosity decreased and bulk density increased with the numbers of infiltration cycle. The hardness of the infiltrated specimen increases with the infiltration cycle and infiltrated depth but seem less sensitive to the number of infiltration cycle at higher infiltration cycle. The friction coefficient and weight loss of the infiltrated specimen are more stable and lower than that of the green specimen. As the number of infiltration cycles increase, average friction coefficients at different infiltrated depth are more similar. Weight losses of specimens at different infiltrated depth are directly related to their average friction coefficient values. The higher the average friction coefficient, the larger are the weight loss. According to the cross-section SEM observations, the pores decreased as the infiltration cycle progressed. X-ray mapping analyses reveal that the efficiency of infiltration decreased with the deeper infiltrated depth. Morphological observations also show that the number of open pores at surface site for these materials decreased and they exhibited a denser and smoother morphology as the number of infiltration cycle increased. Furthermore, as the number of infiltration cycle increases, the friction behavior at the surface site of infiltrated specimens becomes more sensitive to the presentation of gamma-Al2O3 particles. The gamma-Al2O3 particle with higher density and hardness on the sliding surface is more easily to break loose during the wear test and cause the larger weight loss.