Incoloy 907 Alloy (K90907 / N19907 / 2.4665) | Low-Expansion Superalloy for Gas Turbines | FUSHUN METAL

Incoloy 907 (UNS K90907, N19907, W.Nr. 2.4665) is a precipitation-hardenable nickel-iron-cobalt low-expansion superalloy strengthened by niobium and titanium additions. Developed as a second-generation CTX alloy, its defining metallurgical advantage is an exceptionally low coefficient of thermal expansion — approximately 7.6 μm/m·K from 20–400°C — coupled with UTS exceeding 1350 MPa in the aged condition. The alloy belongs to the Incoloy 900-series family (903/907/909), where each successive grade trades off thermal expansion against high-temperature capability; 907 bridges the gap, improving notch-rupture ductility over 903 while retaining a CTE well below conventional nickel superalloys such as Inconel 718 (which expands at ~13.0 μm/m·K). This balance makes Incoloy 907 the established choice for gas turbine components where thermal mismatch control directly translates into fuel efficiency — tighter tip clearances in seals and shrouds, dimensionally stable casings, and lightweight structural parts with superior strength-to-density ratios. Notably chromium-free, the alloy achieves its oxidation resistance through a tightly controlled silicon-aluminum surface layer rather than a chromia scale; as a result, protective coatings are recommended for continuous service above 650°C. At FUSHUN METAL, we produce Incoloy 907 via VIM for precise chemistry control of the narrow Co-Nb-Ti window, followed by VAR for superior inclusion cleanliness, and optionally PESR to refine the solidification structure in large-section ingots exceeding 400 mm diameter. Boron, present at a tightly managed 0.003–0.012% range, segregates to grain boundaries during solidification where it suppresses oxygen embrittlement under sustained creep loading — a trace-element sensitivity FUSHUN METAL monitors with every heat lot released. Two distinct aging routes are available: a tensile-limited schedule (720°C/8h + FC 55°C/h to 620°C/8h) yielding maximum strength above 1350 MPa, and a rupture-limited schedule (775°C/12h + 620°C/8h) trading approximately 10% of tensile strength for significantly improved creep-rupture life at 540°C — we work with each customer to select the heat treatment that best matches their service condition. All material ships under our ISO 9001 and AS9120B accredited quality management system with full melt-route traceability, and each shipment includes chemical analysis, room-temperature and elevated-temperature tensile, hardness, and ultrasonic inspection data per AMS 5917 and ASTM B637.

Typical Applications

Gas Turbine Seals

Labyrinth seals, honeycomb and abradable seal rings, seal carriers — low CTE maintains tight tip clearances for specific fuel consumption reduction

Turbine Shrouds & Rings

Blade outer air seals, ring-seal segments, thermal growth compensation rings — dimensional stability across transients from idle to take-off power

Structural Casings

Compressor and turbine cases, bearing support housings, mid-frames — strength-to-density ratio reduces engine mass

Shafts & Rotor Components

Turbine and compressor shafts, spacer rings, torque cones — maintains concentricity and balance under thermal-mechanical cycling

High-Temp Fasteners

Bolts, studs, lock rings for service to 650°C — excellent stress relaxation resistance preserves joint preload

Glass-to-Metal Sealing

Hermetic feedthroughs, electronic packaging lids, vacuum-tight connectors — CTE matching with borosilicate glasses prevents seal cracking

Precision Instrumentation

Optical bench structures, MEMS packaging, ceramic molding dies — thermal invariance critical for metrology and replication fidelity

Power Generation

Steam turbine seal rings, generator end-bell support structures, hydrogen-cooled alternator retaining rings — creep resistance at 500–550°C