Ongoing demand for advanced aero gas turbine engines with lower fuel burn and commensurate reduced CO 2 emissions require single crystal (SX) superalloys capable of operating at higher gas and metal temperatures beyond the capability of 2 nd generation, 3% rhenium (Re)-containing SX alloys, currently used extensively in commercial and military flight engines. These complex cooled turbine blades and vane castings must have an excellent balance of high temperature mechanical properties, producibility, oxidation/hot corrosion resistance, coating compatibility including TBC performance and phase stability. The highest strength nickel-base SX superalloys currently in production (3 rd generation CMSX-10K ® and CMSX-10N ® alloys) contain 6–7% Re. These highly alloyed, specialty alloys have some application drawbacks including some secondary reaction zone (SRZ) phase instability in the base alloy adjacent to the coatings, low temperature internal oxidation/hot corrosion attack requiring sophisticated dual role internal and external coatings and difficulty in production solution heat treatment. In addition, current 3 rd generation SX alloys have relatively higher density which is a disadvantage in terms of weight and inertia in rotating part applications, and high cost due to the elevated Re content. An improved, lower Re content (4.8%), 3 rd generation SX superalloy, CMSX-4 ® Plus (SLS) has been developed with improved properties and performance over current 3 rd generation SX alloys, while lacking the drawbacks. Coatings have been successfully developed which are compatible with the base alloy and suitable bond coats for TBC application. This paper presents the characterization of CMSX-4 Plus (SLS) alloy, including composition, mechanical and physical properties, oxidation properties and phase stability, along with production status.

Modern turbine engine performance and life cycle requirements demand single crystal (SX) superalloy turbine airfoil and seal components. However, complex SX components, such as vane segments, can result in severe manufacturing cost challenges due to low manufacturing yield. As presented at TURBO EXPO 2002 and 2006, these requirements led to the development of CMSX-486 ® alloy, a grain boundary strengthened SX superalloy with improved creep-rupture strength over SX CM 186 LC ® alloy. This paper will review the unique properties that make this alloy desirable, with particular attention to ongoing developments. Significant market interest has resulted in additional property evaluation, including strain-controlled low cycle fatigue testing which has produced fatigue lives similar to HIP’ed and solutioned CMSX-4 ® SX alloy at 1038°C. This was surprising considering the non-homogeneous microstructure of CMSX-486 alloy, which is used in the as-cast + double aged heat treat condition. Also, burner rig dynamic, cyclic oxidation and Type I hot corrosion results will be presented for CMSX-486 (SLS) [La+Y] alloy in comparison to CMSX-4, CMSX-4(SLS)[La+Y] and CMSX-486 alloys. Scanning electron microscopy analysis shows residual sulfur and phosphorus in CMSX-486 (SLS) [La+Y] are tied up as Y and La carbo-sulfides and phosphides.