Sliding wear behaviors of in situ alumina/aluminum titanate ceramic composites

In situ alumina/aluminum titanate ceramic composites were prepared by spark plasma sintering with two kinds of alumina/titania powders, which are microsized irregular particles (referred to M powder) and microsized spherical particles composed of nanosized grains (referred to N powder). The phase constitution and microstructures of the powders and as-prepared ceramic composites were characterized by using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The sliding wear behaviors of two alumina/aluminum titanate ceramic composites were investigated by ball-on-disc wear test with varied normal loads. The worn surfaces of ceramic composites and counterpart Si₃N₄ balls were characterized by using SEM equipped with X-ray energy dispersive spectroscopy (EDS). The results showed that the wear volume of two ceramic composites increased with increasing the normal load. Under the same normal load, the wear volume of N composite (obtained from the N powder) was higher than that of M composite (obtained from the M powder). Two different behaviors were identified: N composite showed intergranular fracture and grain pull-out; however, the surface reaction layer formed in M composite presented plastic deformation. The different behaviors are controlled by two different mechanisms, brittle fracture mechanism for N and tribochemical reaction mechanism for M. The different wear behaviors for the two ceramic composites were discussed in detail.