TiAl合金表面搪瓷基复合涂层与多弧离子镀NiCrAlY涂层的抗热腐蚀行为对比研究

TiAl intermetallic alloys have attracted great attention for its potential application in preparing low pressure turbine blades in aircraft engine. However, its poor oxidation and corrosion resistance becomes a challenge at temperatures above 800℃, which leads to the developing of protective coatings. Enamel coating is considered as one of the candidates that match the TiAl alloy well, meanwhile provide corrosion protection. Enamel coating has many advantages such as high thermochemical stability, adjustable thermal expansion coefficient and simple preparation process. This study comparatively investigates hot corrosion behavior of the Ti-45Al-2Mn-2Nb alloy, the traditional NiCrAlY coating and the enamel based composite coating in (75%Na₂SO₄+25%NaCl, mass fraction) melted salt. Results indicate that after 80 h of hot corrosion, the bare alloy has completely destroyed. For the NiCrAlY coating, it protects the underlying alloy well by forming a protective Al₂O₃ scale initially. However, serious interdiffusion between coating and substrate results in the degeneration of the coating as well as the scale. At the same time, the basic dissolution of Al₂O₃ film accelerates corrosion. So obvious spallation takes place after 60 h corrosion. The enamel based composite coating shows excellent thermal stability and low corrosion rate. During the whole hot corrosion test, it still retains its original blue glazing color and luster. Furthermore, the enamel coating suppresses the inward diffusion of oxygen and corrosive ions into the alloy substrate, and thus, it protects the TiAl alloy well from corrosion of the molten (75%Na₂SO₄+25%NaCl, mass fraction) salt.