Haynes 188

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. Cryogenic temperatures do not significantly affect the ductility of alloy 188, but strength levels are increased markedly. 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.

Because of its excellent strength, ductility and oxidation resistance, Haynes 188 meets the critical high-temperature material requirements 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.

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.
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.

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 sheets. Cold working prior to aging increases the rate of the aging reaction.