Influences of surface roughness of Li2O-Al2O3-SiO2glass-ceramic on nanoindentation test

The basic theory of nanoindentation testing technique and the Oliver-Pharr method as one of the most useful calculation method were introduced. The hardness, elastic modulus and depth-load curve with different surface roughnesses of glass-ceramic in the Li2O-Al2O3-SiO2 system were measured by nano-indentation test respectively. The test results show that the stability, accuracy and reliability are reduced by the surface roughness: the smoother the sample surface is, the smaller the fluctuation of hardness and elastic modulus is and the higher the coincidence degree of the depth-load curve is. The elastic modulus is decreased with the increasing of the maximum load, which is caused by the plastic deformation of material. Testing results of the nanohardness and elastic modulus of glass-ceramic in the Li2O-Al2O3-SiO2 system are 8.8 GPa and 7.79 GPa respectively on the ultra-smooth surface of the sample(Ra=0.9 nm). The coincidence degree of results of the nanoindentation test is significant to express the super smooth surface integrity.