Potential uses of rapidly solidified alloys in gas turbine engines

Abstract

The benefit of rapid solidification was studied relative to the development of new superalloy compositions for appcation in the hot sections of the gas turbine. Centrifugal atomization ofliquid metal into powder droplets and subsequent freezing by forced convective cooling was used to produce experimental alloys in a rapidly solidified form. Metalworking techniques common to powder-metallurgy processing were used, in turn, to produce bulk stock for test and evaluation. Results with the precipitation-hardening class of superalloys showed that higher concentrations of alloying additions than possible with conventional solidification practices could be achieved by rapid solidification without onset of macrosegregation or deleterious solidification compoundformation. It was found also that certain groups of alloys within this class responded effectively to abnormal grain growth which was controllable to produce aligned crystallographic structures. These combined characteristics were used to develop an alloy composition based on the nickel-aluminium-molybdenum ternary which showed a significant improvement in high-temperature creep resistance over currently available superalloys. Data interpretation suggested that the creep improvement was of the order of 55K.