High Temperature Embrittlement and Its Restraint in Ni-Cu-Al Alloy Ingot
Takanobu MORI and Yoshimi YANAI
Abstract:High temperature embrittlement and its restraint were studied about Ni-Cu-Al alloy ingot for room temperature damper of superconducting generator. Cracking of Ni-Cu-Al alloy ingot occurred when the ingot was given hot forging. It is supposed that the cracking has close relationship to high temperature embrittlement of the Ni-Cu-Al alloy ingot. It was found that increase of Cu, Al, Ti and impurities such as S, Se, Bi, Te and P promote the high temperature embrittlement and reduce elongation at 1050°C in Ni-Cu-Al alloy ingot. However addition of Mg, Zr, B, La and Hf restrain the high temperature embrittlement and increase elongation at 1050°C in Ni-Cu-Al alloy ingot. Based on the present research, the room temperature damper for 70MW class superconducting generator can successfully produced by hot forging after heating up to 1100°C without cracking using the electro-slag remelted ingot with the weight of 21 tons of the developed Ni-12.2%Cu-4.15%Al-0.36%Ti-0.15%C alloy containing 0.011% Mg and 0.039% Zr. Key Words:High temperature embrittlement, Forging cracks, Ni-Cu-Al alloy, Superconducting generator