Segregation behavior of nickel-based superalloy after electron beam smelting

Abstract

The segregation behavior of alloy elements in nicked-based superalloy ingots during electron beam smelting was investigated. Three series of experiments were carried out with different parameters. The micromorphology of the cross section of the ingot and the distribution of alloy elements in the ingot were analyzed. The results show that the melt solidified at the bottom and formed a region of equiaxed grain at the beginning of solidification; the columnar crystal is formed in the middle of ingot with the proceeding of solidification; the region with large grains is formed at the end of the solidification. The segregation of alloy elements is weak during solidification after the nickel-based superalloy is smelted for 10 min with a power of 9 kW. That is, Ni, Ti, Mo and Al show positive segregation with effective segregation coefficient value of 0.994, 0.982, 0.995 and 0.884, respectively; Cr, Co and W show negative segregation with effective segregation coefficient value of 1.051, 1.005 and 1.013, respectively. With the increasing of smelting power and time, the segregation degree of Ni, Cr, Ti, W and Mo is increased, the segregation degree of Al is decreased and the segregation degree of Co shows little change in the ingot.