热腐蚀对GH4169高温合金 δ 相析出和拉伸性能的影响

Influence of Hot Corrosion on Precipitation of δ Phase and Tensile Properties of GH4169 Superalloy

摘要:

分别在650、750、850 ℃热处理条件下，研究了高温合金GH4169在75Na₂SO₄+25NaCl （质量分数）熔盐环境下的热腐蚀行为，之后进行组织表征和力学性能测试。结果表明：随着热处理温度的不断升高，高温合金的抗拉极限强度（UTS）和屈服强度（YS）都出现急剧退化，伸长率显著提高。但在750 ℃条件下，晶界处析出的针状δ相能提高高温合金的强度，导致合金出现沿晶脆性断裂现象，降低了合金的塑性。在650和750 ℃下，腐蚀机理符合II型热腐蚀，但在850 ℃条件下符合I型热腐蚀，2种不同类型腐蚀都促进了基体δ相的析出。

Abstract:

The hot corrosion behavior of the superalloy GH4169 were analyzed in the salt mixture of 75Na₂SO₄+ 25NaCl (wt%) at 650, 750 and 850 °C for 50, 75 and 100 h. Then the precipitation of δ phase and tensile properties of the superalloy at ambient temperature were investigated. Results show that with increasing the heat treatment temperature, the ultimate tensile strength (UTS) and yield strength (YS) of the alloy exhibit a drastic degradation while elongation improves significantly. The needle-shaped δ phase precipitated at the grain boundaries can enhance the strength of the superalloy, and cause intergranular brittle fracture. As a result, the ductility of the superalloy is reduced after exposure at 750 °C. The corrosion mechanism of the alloy conforms to type-II hot corrosion at 650 and 750 °C while to type-I hot corrosion at 850 °C. Both kinds of corrosion can form a corrosion layer and promote the δ phase precipitation.