Mechanical Properties and Microstructure of Melt-Spun Superalloy Ribbons

Abstract

Rapid solidification is expected to produce fine grained superalloys displaying enhanced mechanical properties. The current paper describes the production of melt-spun ribbon.5 of two nickel base superalloys (Rene' 80 and IN738LC) and a cobalt-base superalloy (FSX414). Their microstructures have been characterized by metallographic techniques, electrical resistivity changes and hardness measurements. Tensile p'roperties were determined at ambient and elevated temperatures, where values of the strain rate sensitivity indicate that micrograin superplasticity may be occurring.

Superplastic MAR-M247 LC superalloy made by compaction of rapidly solidified ribbons

“…The grain size was less than 1 Jlm (Fig. 1c), and precipitation reactions were well suppressed except at grain boundaries, which were decorated with small M 23 C 6 precipitates. Table 2 summarizes the main characteristics of the RS ribbons and compares them with those of DS cast bar samples of MAR-M247 LC.…”

“…6. The incipient melting point of the ribbons was determined by optical metallography of the ribbons exposed to temperatures near the incipient melting point of the conventional castings.…”

“…4 ,6 For instance, superplastic behaviour has been observed in hightemperature (900-950°C) tensile tests on nickel-base superalloy ribbons. 6 Since the solidification rate is constant over the entire ribbon length, the yield of ribbons of highly refined microstructures from an ingot would markedly exceed that achievable by atomizing processes. The melt spinning method is relatively simple and economical, yet consolidation of superalloy RS ribbons has not been studied thoroughly.7 The objectives of the present work were to demonstrate that full densification of the RS ribbons is possible, and that the superplastic behaviour can be preserved in the consolidated form despite the hightemperature mechanical processing.…”