1984-10-01

Development of Fine Grain Cast MAR-M 247 Axial and Radial Turbine Wheels 841515

Integrally cast turbine wheels are used extensively in turboprop and auxiliary power gas turbine engines. Historically, these wheels have been conventionally cast from IN 100 or IN713LC nickel-base super alloys.
A significant increase in mechanical properties, particularly low cycle fatigue, is achieved in axial and radial turbine wheels when conventionally cast using a higher strength nickel-base superalloy, MAR-M 247. Additional low cycle fatigue property improvement has been demonstrated by changing to a new casting process that produces a finer grain structure.
Fine grain castings were produced using a mold agitation technique that induces grain inoculation throughout the melt and results in exceptional grain uniformity regardless of cross sectional variations.
This paper discusses the differences between this fine grain process versus a conventional cast process, and shows the benefits to be gained in terms of higher mechanical properties/longer cyclic lives and present potential pitfalls/trade-offs.

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