镍基690合金时效过程中晶界碳化物的形貌演化

EVOLUTION OF CARBIDE MORPHOLOGY PRECIPITATED AT GRAIN BOUNDARIES IN Ni-BASED ALLOY 690

用SEM研究了含有高比例低∑重位点阵(CSL)晶界的镍基690合金在715℃时效过程中不同类型晶界上碳化物的形貌演化.结果表明:低∑CSL晶界与一般大角晶界上碳化物的形貌演化特征有明显区别.晶界上的碳化物粒子尺寸随∑值降低而减小,共格∑3晶界上的小尺寸碳化物在长时间时效后无明显变化;非共格∑3晶界和∑9晶界附近都观察到板条状碳化物,并随时效时间延长明显长大,非共格∑3晶界两侧都存在碳化物板条,而∑9晶界上的碳化物板条只在晶界一侧生长;∑27晶界与一般大角晶界处的碳化物形貌相似,在晶界附近未观察到板条状碳化物.

The effects of grain boundary characters on the morphology evolution of the intergranular carbide in Ni-based alloy 690 with high proportional low E coincidence site lattice （CSL） boundaries aged at 715 ℃ for 2-200 h were investigated by SEM. The results show that the sizes of intergranular carbides decrease with ∑ value decreasing, and only fine carbides at coherent ∑3 are almost not changed after aging for 200 h. Plate-like carbides precipitated near both incoherent ∑3 and ∑9 boundaries, and the carbide plates grow bigger with the aging time prolonging, in which the former precipitated near both sides of incoherent ∑3 boundary and the latter precipitated near only one side of ∑9 boundary. The morphology of carbide precipitated at ∑27 boundary is similar to that precipitated at the general high angle grain boundary, and no plate-like carbides are observed near these boundaries.