电子束选区熔化增材制造TiAl合金的高温硬度及氧化行为研究

High temperature hardness and oxidation behavior of TiAl alloy fabricated by electron beam selective melting additive

摘要:

钛铝合金是航空航天领域具有广阔应用前景的轻质高温合金，电子束选区熔化（EBM）增材制造技术是制备复杂结构TiAl合金有效途径，但目前对其高温性能研究较少。本文重点研究了电子束选区熔化增材制造Ti-48Al-2Cr-2Nb合金的显微组织、高温硬度及其高温氧化行为。结果表明，EBM成形Ti-48Al-2Cr-2Nb合金呈现出由等轴γ晶粒和双相区组成的独特层状组织；在800 ℃下恒温氧化100 h，表现出较低的氧化速率常数，形成的氧化膜主要由TiO2、Al2O3及TiO2 / Al2O3混合交替层组成，抗氧化性能优于传统方法制备的Ti-48Al-2Cr-2Nb合金和其他TiAl合金。此外，900℃以下，该合金具有良好的高温硬度，显微硬度随温度的升高未发生明显的下降趋势。

Abstract:

TiAl alloy is a lightweight superalloy with broad application prospects in aerospace field. Electron beam selective melting(EBM) additive manufacturing technology is an effective way to prepare TiAl alloy with complex structure. However, there are few studies on high temperature properties of TiAl alloy. In this paper, the microstructure, high-temperature hardness and high-temperature oxidation behavior of Ti-48Al-2Cr-2Nb alloy fabricated by electron beam selective melting additive are mainly studied. The results show that the Ti-48Al-2Cr-2Nb alloy formed by EBM exhibits a unique layered structure composed of equiaxed γ grains and double phase regions. After isothermal oxidation at 800 °C for 100 h, this alloy shows a low oxidation rate constant, and the formed oxide film is mainly composed of TiO2, Al2O3 and TiO2 / Al2O3 mixed alternating layers. The oxidation resistance is better than that of Ti-48Al-2Cr-2Nb alloy and other TiAl alloy prepared by traditional methods. In addition, this alloy has good high temperature hardness at below 900 ℃, and the microhardness does not decrease significantly with the increase of temperature.