Effect of Cr2O3 on the Microstructure and Oxidation Resistance of Enamel Coating with TC4 Titanium Alloy

Abstract

By adding 0 % to 50 % Cr₂O₃ ceramic particles, the enamel composite coating is produced on the surface of TC4 titanium alloys. The detection analysis indicates that with the increase of the amount of Cr₂O₃ particles added, the density of enamel coating increases as well, and the amount of the pore holes decreases at the same time, but the enamel coating becomes porous with more than 30 % of the amount of Cr₂O₃ particles added. The main crystalline phases of enamel coating are NaAlSi₃O₈ and Ca₂SiO₄, whereas the Cr₂O₃ ceramic particles added are mainly presented as an independent phase, and part of the particles are in the form of Ca₅Cr₃O₁₂ phase after the reaction. The enamel coating with 30 % Cr₂O₃ ceramic particles added has the best high-temperature oxidation resistance, mainly because the main crystalline phase of NaAlSi₃O₈ is changed into Na₂Si₂O₅ during the high-temperature oxidation, which is beneficial to the self-healing of the coating.