Machine Casting of High Temperature Alloys for Turbine Engine Components
Final rept. 1 Mar 1976-30 Apr 1977
PRATT AND WHITNEY WEST PALM BEACH FL GOVERNMENT PRODUCTS DIV
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A program has been initiated to evaluate the capability of machine casting for fabricating components for gas turbine engines such as compressor airfoils. The goal is to evaluate the capability of the process to produce an end product of high quality on an economic basis. During this contract, machine casting activity consisted of equipment modification to an existing machine casting unit which included mechanization of the process. Concurrently, statistical assessment of process parameter effects using Rheocast Haynes Alloy 31 cobalt-base alloy as a vehicle was performed. Machine casting preforms containing varying volume fractions of solid were inspected at different die temperatures and injection speeds and were evaluated both non-destructively and metallographically. Results indicated that quality of high volume fraction parts was improved using high injection speeds and low die temperatures. An alternate die design was also evaluated. Heat treatment response studies were also performed on machine cast specimens. Results indicated that long term anneals followed by aging yielded microstructures similar to cast and heat treated Haynes 31. Mechanical property evaluation consisted of room temperature, 1000 F and 1450 F tensile testing, 1450 F stress rupture and room temperature high cycle fatigue HCF testing. Tensile data indicated that tensile design goals could be achieved. Stress rupture and HCF goals were achieved through the use of hot isostatic capacition to reduce internal porosity in the machine cast specimens.
- Fabrication Metallurgy