Effect of ion beam-sputtered silica films on the wear behavior of ion-implanted silicon nitride

Silicon dioxide films were ion beam-sputtered on to the surface of ion-implanted and unimplanted silicon nitride with different microstructures. The tribological properties of these materials were evaluated using a block-on-ring wear tester under nonlubricated conditions against commercially available silicon nitride materials, and were related to the effect of surface modification by these ion beam techniques. The ion beam-sputtered silicon dioxide film resulted in a dramatic reduction of specific wear rate in each sample, accompanied by low friction coefficient. From surface roughness analysis and cross-sectional transmission electron microscopy observations, it was clarified that the silica film itself was easily worn but a thin silica film with a thickness of 10–20 nm was retained and prevented the material beneath the film from wearing. A specific wear rate of 1.59×10−10 mm2/N and low friction coefficient of 0.2 were easily obtained even in conventional silicon nitride by the silica coating.