材料期刊网

本文报导了采用自行设计的液态锂静态腐蚀试验装置,对常用的5种高温合金(GH-30、GH-128、GH-37、GH-49和K-38)在800°、850°和900°进行了20小时对比筛选试验。用失重和晶界渗透深度来评价其抗蚀性;用扫描电镜(SEM)观察表面腐蚀形貌,并以能量色散谱仪(EDS)分析相成份;用电子探针(EMPA)和离子探针(IMA)鉴别晶界渗透腐蚀产物,结果表明;试验合金的腐蚀失重都随温度升高而增加;GH-49和K-38失重较小,GH-30失重较大。γ′相强化的合金(GH-37、GH-49和K-38)发生锂沿晶界渗透,并随温度升高而加深。固溶强化合金的腐蚀特征是镍的择优离析和Kirkendall效应,使基体产生空穴,最后形成α-Cr(Mo,w)骨架状多孔松散层。由γ+γ′两相组成的γ′相强化合金,晶界主要足由碳化物的γ′包膜组成,由于锂沿晶界渗透形成Li_2C_2等化合物,并发生γ′包膜的择优离析,使Li_2C_2两侧形成腐蚀深沟,这种包围着晶粒的深沟被打通后将使整个晶粒脱落,这是造成γ′相强化合金失重的主要原因。

Five superalloys(GH-30, GH-128, GH-37. GH-49 and K-38)were subjected to screening tests in liquid lithium at temperatures of 800°, 850° and 900℃ respectively. The corrosion resistance was evaluated by gravimetric method and by measuring the depth of grain boundary penetration. The results show that the weight losses for all these five alloys increase with temperature, GH-49 and K-38 having the least loss and GH-30 having the biggest loss. For the γ′strengthered alloys (GH-37, GH-49 and K-38), it is found that lithium penetrates along the grain boundaries. For the solid solution strengthered alloys, on the other hand, nickel is preferentially leached into lithiumand Kirkendall effect is observed with voids in the base alloy, thus causing the formation of a loose and porous α-Cr(Mo. W) skeleton layer. In the γ′t strengthered alloys which are composed of (γ+γ′) phases, the grain boundary mainly consists of carbide enveloped by a γ or γ′ film. The penetration of lithium along the grain boundaries, results in the formation of compounds such as Li_2C_2 which are insoluble in Li. Preferential leaching of the γ or γ′ film took place, thereby forming deep corrosion channels around Li_2C_2. When such channels connect each other, the isolated particles would fall off, which accounts for the weight loss of such alloys.