G.L. Erickson and K. Harris

Cannon-Muskegon Corporation
[SPS Technologies]

Muskegon, Michigan USA

ABSTRACT

Industrial gas turbine engine producers are introducing directionally solidified (DS) and single crystal (SX) cast turbine blades in new engines due to the potential performance benefits they provide relative to equiaxed components. Initial industry-wide work evaluating the DS creep properties and castability of existing equiaxed industrial turbine production alloys, such as IN 939 and IN 738 LC, has led to the belief that new DS and SX alloy development will be necessary to fulfill the advancing material design requirements.

Specifically, stationary gas turbine producers who are planning to utilize DS and SX cast components seek alloys capable of providing better elevated temperature creep strength than IN 939 and bare corrosion resistance comparable to IN 738 LC/IN 792. The blended level of strength and hot corrosion requirement varies amongst the engine producers, due in part to the variation of fuel-type to be used. Additionally, candidate materials necessarily provide DS/SX castability adequate to produce components to about 6-26" (152-660 mm) in length, along with good microstructural stability.

Two production Cannon-Muskegon alloys, CM 247 LC® and CMSX-4® are under evaluation and/or being utilized by several industrial turbine producers; primarily in applications utilizing relatively clean fuels. Alternatively, several high strength, corrosion resistant alloys, both DS and SX, are under experimental development with target designs aimed toward providing high strength in conjunction with greater bare hot corrosion resistance in comparison to CM 247 LC and CMSX-4. The target designs aim toward providing varied blends of strength/hot-corrosion capability.

Experiences involving the industrial turbine application of the CM 247 LC and CMSX-4 alloys are reported in tandem with discussion of selected alloy target-design detail.