Haynes 188 Nickel Based Superalloys

Haynes 188 is a cobalt-based alloy which possesses a unique combination of properties. It has excellent high temperature strength and oxidation resistance to 2100°F (1150°C) combined with good post-aging ductility.

Alloy 188 has average room temperature tensile properties in the bright annealed condition of 137.2 ksi (946 MPa) ultimate strength, 67.3 ksi (464 MPa) yield strength and 53% elongation. At 1800°F (980°C) the alloy has ultimate and yield strengths of 35.2 ksi (243 MPa) and 19.0 ksi (131 MPa), respectively, with 59% elongation. Cryogenic temperatures do not significantly affect the ductility of alloy 188, but strength levels are increased markedly.

The excellent oxidation resistance of Haynes 188 results from minute additions of lanthanum, which modifies the protective oxide scale in such a manner that the oxide becomes extremely tenacious and retards diffusion when exposed to temperatures through 2100°F (1150°C).

Haynes 188 exhibits good ductility after prolonged exposure at temperatures of 1200, 1400, and 1600°F (650, 760 and 870°C) for 16,000 hours.

Inconel® alloy 188 (also known as Haynes 188) is a cobalt-nickel-chromium-tungsten alloy that may be readily fabricated for aerospace and commercial gas turbine engine applications, including combustion cans, flame holders, liners, transition ducts, and afterburner parts.

Application:

Because of its excellent strength, ductility and oxidation resistance, Haynes 188 meets the critical high-temperature material requiredments for gas turbine applications as well as many of those in the airframe, chemical and nuclear fields. Typical uses are as transition ducts, combustor cans, spray bars, flame-holders and afterburner liners in jet engines.

Workability:

Haynes 188 can be forged and, because of its good ductility, can be readily cold formed. It can be welded by both manual and automatic welding methods including electron beam, gas tungsten arc (TIG) and resistance welding. Alloy 188 exhibits good restraint welding characteristics.

Heat-Treatment:

Wrought forms of Haynes 188 are furnished in the solution heat-treated condition unless otherwise specified. Alloy 188 is normally solution heat-treated at 2150°F +/-25°F (1177°C +/-14°C) and rapid air cooled or water quenched. Bright annealed products are cooled in hydrogen.

Cold-Work and Aging:

Because of its relatively high strain hardening coefficient, Haynes 188 can be easily strengthened by cold deformation. Strengthening is further enhanced by aging the cold-worked structure near 1000°F (540°C) for a period of 4 to 16 hours. This combination of treatments increases both the room and elevated tensile strength of alloy 188 sheet. Cold working prior to aging significantly increases the rate of the aging reaction.

Microstructure:

Haynes 188 has a stabilized face-centered-cubic matrix containing nominally 22% Cr, 0.05% La and 0.4% Si to promote oxidation resistance. W at 14% is added for solid solution strengthening. Strengthening is further enhanced by the precipitation of M6C and M23C6 carbides. Intermediate temperature ductility is achieved by deterring the formation of a A2B Laves-type phase through selective alloying.

Physical Properties:

Dynamic Modulus of Elasticity:

Average Tensile Data:

*Bright annealed sheet 0.029-0.050". Strain rate was 0.005 in/in/minute to 0.2% yield point and .05 in/in/minute to failure.

Average Rupture Data:

Average Creep Data: