Microstructure of spray-formed superalloy FGH4095

Abstract

Spray-forming technology can produce billets with similar microstructure and higher productivity compared with the P/M process. The nickel based superalloy FGH4095 billet was produced by spray-forming with nitrogen as atomization gas. The pressure of the atomization gas and the temperature of the deposit zone were recorded. The compactness of the deposit was characterized by quantitative metallography and Archimedes method. The grain structure of substrate and the size and morphology of ' phase were observed. Results show that the density of the deposit produced by nitrogen spray forming reaches about 99% and little amount of pores with diameters about 12 m could be detected in the deposit matrix. While, pores could be enclosed by HIP and near iso-thermal forging process; Nitrogen was existed as carbonitride with diameters less than 1 m. The average grain size of the equiaxed grains in the interior of the deposit is about 2040 m, while the grains near the surface of the deposit are finer with average grain size about 13um; the primary ' phase which has diameters about 0.30.5 m possesses irregular block feature. The microstructure of the spray deposit is related to the temperature history of the alloy during the spray forming process.