Why Inconel 718 for Turbine Discs
Turbine discs are among the most safety-critical components in gas turbine engines. They rotate at speeds exceeding 10,000 RPM while enduring temperatures above 1,000°F and centrifugal stresses measured in tens of thousands of PSI. Inconel 718 is the universal choice for this application because its precipitation-hardened microstructure delivers tensile strength above 180 ksi, yield strength exceeding 150 ksi, and exceptional low-cycle fatigue life—the property that directly governs disc service lifetime. The alloy maintains these properties up to approximately 1,300°F, which covers the operating envelope of compressor and intermediate-pressure turbine discs.
Forging Process for Turbine Discs
CastAlloy produces Inconel 718 turbine discs through closed-die forging on hydraulic presses with capacities up to 2,000+ metric tons. The forging process refines the grain structure through controlled plastic deformation, producing 20 to 40 percent higher fatigue strength compared to cast alternatives. Billets are heated to 1,700–2,050°F using medium-frequency induction furnaces for uniform temperature distribution. The forging sequence is designed to achieve specific grain flow patterns that align with the disc's stress field, maximizing fatigue life in the bore and web regions where stresses are highest. Post-forging solution treatment at 1,750°F followed by double aging (1,325°F + 1,150°F) produces the optimal gamma-prime and gamma-double-prime precipitate distribution.
Quality and Inspection
Every Inconel 718 turbine disc undergoes comprehensive inspection including ultrasonic testing to verify internal integrity and detect subsurface discontinuities, fluorescent penetrant inspection for surface-breaking defects, mechanical property verification through tensile and hardness testing of test coupons, microstructural evaluation to confirm proper grain size and precipitate distribution, and dimensional verification on coordinate measuring machines. Full material traceability from billet certification through final inspection is maintained under our ISO 9001:2015 quality management system with processes aligned to AS9100 aerospace requirements.
CastAlloy Turbine Disc Capabilities
Our Inconel 718 turbine disc capabilities span from small auxiliary power unit (APU) discs weighing a few pounds to large industrial gas turbine discs weighing several hundred kilograms. We provide complete manufacturing support from engineering design collaboration through forging, heat treatment, CNC machining to final dimensions, and full NDT inspection. Whether you need prototype development or series production, CastAlloy delivers the quality, precision, and documentation that aerospace and power generation applications demand. Contact our engineering team to discuss your turbine disc requirements.