Laser surface nitriding of yttria stabilized tetragonal zirconia

Surface nitriding of yttria (Y2O3) stabilized tetragonal zirconia (t-ZrO2) has been performed using the pulsed Nd-YAG laser irradiation in the nitrogen atmosphere. The results show modifications of the crystallographic structure between the original tetragonal zirconia and the treated one. Nitrogen atoms enter in the zirconia substituting to oxygen atoms in the network. X-ray diffraction and Raman spectra show an efficient transformation of the t-ZrO2 at the surface that exhibit the typical yellow-gold color of ZrN with high hardness and wear resistance. The hardness measured with Vickers indenter bears a high value of about 1409 HV. Nitriding is accomplished by the formation of a few micron thick gradient layer of ZrN structure on the top and a partial transformation of t-ZrO2 into cubic zirconia (c-ZrO2) beneath deep in the bulk due to nitrogen concentration gradient.