A technician compares materials used in a turbofan engine's compressor and turbine sections. Which statement correctly describes typical material selection?
- AFront compressor stages use nickel-based superalloys for high strength at low weight, while turbine discs use aluminum for heat resistance
- BFront compressor stages use ceramic matrix composites exclusively, while turbine sections use titanium alloys
- CBoth compressor and turbine sections use the same aluminum alloys throughout for weight savings
- DFront compressor stages commonly use titanium alloys for their strength-to-weight ratio, while turbine discs and blades use nickel-based superalloys for high-temperature strength
Show answer & explanationAnswer & explanation
Correct answer: D. Front compressor stages commonly use titanium alloys for their strength-to-weight ratio, while turbine discs and blades use nickel-based superalloys for high-temperature strength
Front compressor stages operate at relatively lower temperatures, so lightweight, strong titanium alloys are commonly used. Turbine discs and blades face extreme temperatures and stresses, requiring nickel-based superalloys (and sometimes single-crystal castings) for high-temperature strength and creep resistance.
Why the other options are wrong
- A. Aluminum cannot withstand turbine section temperatures.
- B. Ceramic matrix composites are used selectively, not exclusively, and titanium is unsuitable for turbine hot sections.
- C. Aluminum is unsuitable for turbine hot-section temperatures.
Turbine Engine Material Selection
Titanium alloys are typically used in cooler front compressor stages for strength-to-weight benefits, while nickel-based superalloys are used in the hot turbine section for high-temperature strength and creep resistance.
- Titanium: front compressor, moderate temps
- Nickel superalloys: turbine discs/blades, high temps
- Some turbine blades use single-crystal casting
- Ceramic matrix composites emerging in hot sections
Memory trick: Cool front = titanium, hot back = nickel superalloy