AERO ENGINE TEST EXPERIENCE WITH CMSX-4(R) ALLOY SINGLE-CRYSTAL TURBINE-BLADES

A team approach involving a turbine engine company (Rolls-Royce), its single-crystal casting facilities, and a superalloy developer and ingo t manufacturer (Cannon-Muskegon), utilizing the concepts of simultaneo us engineering, has been used to develop CMSX-4 alloy successfully for turbine blade applications. CMSX-4 alloy is a second-generation nicke l-base single-crystal superalloy containing 3 percent (wt) rhenium (Re ) and 70 percent volume fraction of the coherent gamma' precipitate st rengthening phase. Its finely balanced composition offers an attractiv e range of properties for turbine airfoil applications. In particular the alloy's combination of high strength in relation to creep-rupture, mechanical and thermal fatigue, good phase stability following extens ive high temperature, stressed exposure and oxidation, hot corrosion a nd coating performance, are attractive for turbine engine applications where engine performance and turbine airfoil durability are of prime importance. The paper details the single-crystal casting process and h eat treatment manufacturing development for turbine blades in CMSX-4 a lloy. Competitive single-crystal casting yields are being achieved in production and extensive vacuum heat treatment experience confirms CMS X-4 alloy to have a practical production solution heat treat/homogeniz ation ''window.'' The creep-rupture data-base on CMSX-4 alloy now incl udes 325 data points from 17 heats including 3630 kg (8000 lb) product ion size heats. An appreciable portion of this data was machined-from- blade (MFB) properties, which indicate turbine blade component capabil ities based on single-crystal casting process, component configuration , and heat treatment. The use of hot isostatic pressing (HIP) has been shown to eliminate single-crystal Casting micropores, which along wit h the essential absence of gamma/gamma' eutectic phase, carbides, stab le oxide, nitride and sulfide inclusions, results in remarkably high m echanical fatigue properties, with smooth and particularly notched spe cimens, The Re addition has been shown not only to benefit creep and m echanical fatigue strength (with and without HIP), but also bare oxida tion, hot corrosion (sulfidation), and coating performance. The high l evel of balanced properties determined by extensive laboratory evaluat ion has been confirmed during engine testing of the Rolls-Royce Pegasu s turbofan.