Study on the Evolution of the gamma ' Phase and Grain Boundaries in Nickel-Based Superalloy during Interrupted Continuous Cooling

The formation of the irregular gamma & PRIME; precipitates in the nickel-based superalloy Waspaloy was investigated during the continuous cooling, which is relevant to the cooling rates and interrupted temperature. The morphology of the gamma & PRIME; precipitates was observed to change from a dispersed sphere to the flower-like one with the decreasing of the cooling rates. It was found that there are three modes of transportation of the solute atoms involved in relation to the gamma & PRIME; precipitates: dissolution from the small gamma & PRIME; precipitates to the gamma matrix, diffusion to the large gamma & PRIME; precipitates from the matrix, and the short distance among gamma & PRIME; precipitates close to each other. Meanwhile, the slower cooling rates tend to result in the serrated grain boundaries, and the wavelength between successive peaks (lambda) and the maximum amplitude (A) are larger with the decreasing of the cooling rates. The content of the low sigma CSL boundaries increases with the decreasing of the cooling rates, which is of great benefit in improving the creep property of the Waspaloy.