钛合金表面直接激光熔覆Al2O3-13%TiO2涂层互熔稀释特性

运用固体与分子经验电子理论(EET),对Nb、Ti、V3种不同Fe-M-C合金系fcc铁基体(α)、析出的B1型碳化物(ξ)和α/ξ共格界面区(σ)各晶胞价电子结构进行了计算;在此基础上,通过共价键能将EET与离散点阵平面/最近邻断键(DLP/NNBB)模型结合,对以上3种不同合金系的B1型碳化物与bcc铁基体共格界面能进行了理论计算与分析.计算结果表明,合金元素在α/ξ界面区产生偏聚作用,增强了共价键络,产生了固溶强化作用;随着含碳量的增加,C-M偏聚作用增强,界面能逐渐增大;α/ξ共格界面能随温度增加而略有下降,变化范围为1.10～1.45 J/m2,与相关文献所得结果一致,Fe-Nb-C合金系α/ξ共格界面能随温度下降最快;Fe-Nb-C合金系α/ξ共格界面能最大,故Nb 元素对相变过程晶粒细化效果最好;随着合金元素含量的增加,固溶于铁基体和界面区的含碳量减少,偏聚作用减小,α/ξ共格界面能缓慢下降.

Dilution Characters of Al2O3-13wt%TiO2 Coating by Direct Laser Cladding on Titanium Alloy

The direct cladding of Al2O3-13wt%TiO2 coating on Ti-6Al-4V alloy substrate was performed with coaxial laser cladding. OM and EMPA were used to examine the dilution characters, microstructure and element distribution of the cross-sections of cladding samples. The results show that after the irradiation the dilution zone (DZ) is likely to form the distinct pattern that at the edges of single clad pass the ceramic coating penetrates into the substrate, while in the middle of the pass the melting metal protrudes from the substrate into the ceramic coating. Moreover, there are many ceramic particles distributing in the DZ zone, and the layer is prone to produce more cracks with the cluster formation of the ceramic particles. The coating with low dilution and no obvious cracks is obtained by optimizing the processing parameters