Preparation and Characterization of a new Glass-Ceramic glaze for Ti6Al4V Alloy

A new silicate-based glass-ceramic coating (51SiO(2)-10Al(2)O(3)-5ZrO(2)-(2)Y2O(3)-20B2O(3)-7Na2O-5K(2)O in mol %) was prepared, especially for improving tribological properties along with the soulless metallic outward appearance of Ti6Al4V alloy. For this, the based glass composition was designed so that there would be no need to use a bond coat or pre-preparation like oxidation of the beneath substrate before the coating process. Here, the effect of different holding times of 40, 80 and 120min at firing temperature of 900C on the physical and mechanical properties was inspected. The physical properties of the coating layers were characterized by means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) equipped with EDS and Atomic Force Microscopy (AFM), and also the mechanical properties of the coated samples were investigated by Nanoindentation, Vickers microhardness, and tribological experiments. The results revealed that the holding time of 120min at the firing temperature of 900C can be considered as the optimum point for sintering and crystallization this glass-ceramic coating; holding the coated samples below 40min at this firing temperature led to a porous structure due to insufficient time to outgoing of gaseous bubbles, and also above 960C a cracked structure due to substrate alpha/beta transformation. Detection of Ti5Si3 phase in XRD analysis can be considered as a positive sign of formation of a chemical bonding between the coating and the beneath substrate. By depositing the coating layer, the Vickers microhardness improved from 4.2GPa for the bare substrate to 9.9GPa for the coated sample. Additionally, the wear sliding test revealed that the weight loss of the coated samples after 300m was reduced approximately 14 times than the bare Ti6Al4V substrates.