ABSTRACT
Refractory metal, especially Mo or W, is important in superalloys because it has many beneficial effects such as retardation of γ` coarsening during hot exposure, thus making the control of γ` size control possible. In this study, Ni-base superalloy powders are produced by Ar-gas atomization, and extruded bars are manufactured, and the variation of microstructure and mechanical properties with Mo content are thoroughly examined. As-solidified microstructures of superalloy powders have dendritic structures independent of powder particle size, and secondary dendritic arm spacing of the particles does not change with Mo content. Volume fraction of γ` increases from 55% to 65% with increase of Mo content from 0.97wt% to 4.64wt%, and does not increase when Mo content is more than 4.64wt%. With increasing Mo content, U. T. S. increases from 900 ㎫ to 1000 ㎫ at 650℃, from 600 ㎫ to 700 ㎫ at 750℃ and the rate of increment is reduced above 850℃.
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