CMSX-486^® Alloy Update

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.