Effect of Processing Variables on Powder-Metallurgy Rene 95

Abstract

A Rene' 95 powder-metallurgy processing study was conducted to determine a cost effective method for producing Rene' 95 disks and also gain an understanding of the effects of powder-processing variables on properties and producibility. Variables studied included powder manufacturing method (argon atomiza-tion, rotating electrode, and H2/ vacuum atomization), particle-size distribution, consolidation techniques (extrusion vs. HIP), forging reductions and temperatures, and heat-treatment schedules. Forging multiples ranged from four pounds for the laboratory portion of the investigation to over four hundred pounds for the engine disks. For the parameters studied, decreases in powder particle size resulted in increases in 1200F stress-rupture lives of both extruded and HIP consolidated powders. Tensile properties of extruded compacts were superior to HIP properties and were unaffected by prior particle size while HIP compact tensile properties were inversely proportional to powder size. Subsequent forging of the compacts greatly minimized differences caused by the original powder size distribution and resulted in comparable tensile strengths for both consolidation methods. Stress-rupture lives and ductilities, however p were superior for the HIP forgings. Forging at lower temperature (1975F VS. 2O75iF) and at higher forging reductions improved tensile properties. Forgeability of the consolidated powders was good for virtually all conditions. In summary, the best powder metallurgy forging properties were achieved using powders having a fine particle size distribution that were consolidated at 2OqOF (below y8 solvus) and forged at 1975F. Introduction Jet-engine compressor and turbine rotor disks are the most critical and highly stressed major components in today's advanced engines. They are produced from complex highly alloyed precipitation strengthened superalloys that, because of their alloy content, are difficult to produce and consequently are very expensive. The powder metallurgy process as a method for producing these parts offers significant advantages over conventional cast plus wrought methods used until now. These advantages may be categorized as: 1) Lower Costs because of improved metal utilization, decreased forging operations and better forgeability and 2) Improved Properties attributed to the inherent homogeneity of powders. The powder metallurgy processes that may be used to produce these components cover a wide spectrum, but two of these have found the most favor. One is extrusion of powders followed by forging and the other is hot-isostatic pressing (HIP) plus forging. The work reported here is centered about these two generalized processes. Powder metallurgy variables utilizing these processes were investigated to determine their effect upon properties and producibility of a superalloy disk material, Rene' 95, with the intention of establishing a cost effective method for producing such disks.