Thermal evolution behavior of carbides and {gamma} Prime precipitates in FGH96 superalloy powder

• Published in: Materials characterization 2012-05, Vol.67 (Complete)
• Main Authors: Zhang Lin, Liu Hengsan, He Xinbo, Rafi-ud-din, Qu Xuanhui, Qin Mingli, Li Zhou, Zhang Guoqing
• Format: Article
• Language: English
• Subjects: ANNEALING; CARBIDES; COALESCENCE; DENDRITES; DIFFUSION; GRAIN BOUNDARIES; GRAIN GROWTH; HEAT RESISTING ALLOYS; MATERIALS SCIENCE; MORPHOLOGY; NICKEL BASE ALLOYS; PARTICLE SIZE; PARTICLES; POWDER METALLURGY; POWDERS; PRECIPITATION; SOLIDIFICATION; SOLIDS
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/J.MATCHAR.2012.02.014

The characteristics of rapidly solidified FGH96 superalloy powder and the thermal evolution behavior of carbides and {gamma} Prime precipitates within powder particles were investigated. It was observed that the reduction of powder size and the increase of cooling rate had transformed the solidification morphologies of atomized powder from dendrite in major to cellular structure. The secondary dendritic spacing was measured to be 1.02-2.55 {mu}m and the corresponding cooling rates were estimated to be in the range of 1.4 Multiplication-Sign 10{sup 4}-4.7 Multiplication-Sign 10{sup 5} K{center_dot}s{sup -1}. An increase in the annealing temperature had rendered the phase transformation of carbides evolving from non-equilibrium MC Prime carbides to intermediate transition stage of M{sub 23}C{sub 6} carbides, and finally to thermodynamically stable MC carbides. The superfine {gamma} Prime precipitates were formed at the dendritic boundaries of rapidly solidified superalloy powder. The coalescence, growth, and homogenization of {gamma}' precipitates occurred with increasing annealing temperature. With decreasing cooling rate from 650 Degree-Sign C{center_dot}K{sup -1} to 5 Degree-Sign C{center_dot}K{sup -1}, the morphological development of {gamma} Prime precipitates had been shown to proceed from spheroidal to cuboidal and finally to solid state dendrites. Meanwhile, a shift had been observed from dendritic morphology to recrystallized structure between 900 Degree-Sign C and 1050 Degree-Sign C. Moreover, accelerated evolution of carbides and {gamma}' precipitates had been facilitated by the formation of new grain boundaries which provide fast diffusion path for atomic elements. - Highlights: Black-Right-Pointing-Pointer Microstructural characteristic of FGH96 superalloy powder was investigated. Black-Right-Pointing-Pointer The relation between microstructure, particle size, and cooling rate was studied. Black-Right-Pointing-Pointer Thermal evolution behavior of {gamma} Prime and carbides in loose FGH96 powder was studied.