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Abstract 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.
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Received: 25 June 1985
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