Udimet - Model 188 - High Performance Alloys
From Udimet/Udimar - High Performance Alloys
UDIMET alloy 188 (UNS R30188) is a cobalt-base alloy with excellent high-temperature strength and good oxidation resistance to 2000°F (1093°C). The high chromium level coupled with small additions of lanthanum produce an extremely tenacious and protective scale. The alloy also has good sulfidation resistance and excellent metallurgical stability as displayed by its good ductility after prolonged exposure to elevated temperatures. Good fabricability and weldability combine to make the alloy useful in gas turbine applications such as combustors, flame holders, liners and transition ducts.
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Products Details
Microstructure
UDIMET allov 188 has a stabilized face-centered cubic matrix. Chromium (22%), lanthanum (0.05%) and silicon (0.4%) promote oxidation resistance. Solid solution strengthening is provided by tungsten (14%). Strengthening (see heat treatment details) is further enhanced by the precipitation of M^C andN^Cg type carbides.
Fabricating
UDIMET alloy 188 has good fabricability. Forming, machining and welding can be carried out by standard methods.
Cold Forming
It is preferable to cold-work the alloy for bending, deep drawing and spinning of components. This is facilitated by the excellent ductility of the alloy, however, high forces may be required to achieve such processing, due to the inherent strength of the alloy. It may therefore be necessary to interstage anneal the material after each step of processing due to the high work hardening rate of the alloy.
Joining
UDIMET alloy 188 can be welded by both manual and automatic welding methods, including shielded metal-arc, gas tungsten-arc (TIG) and gas metal-arc (MIG).
Heat Treatment
UDIMET alloy 188 is normally annealed at 1177°C (2150°F) and rapid air-cooled or water-quenched. The material can be further strengthened by cold deformation, with enhancement of strength achieved by aging at 540°C (1000°F) for 4 to 16 hours. Note that cold working prior to aging significantly increases the rate at which age hardening can be achieved.
Applicable Specifications
UDIMET alloy 188 is designated as UNS R30188. Contact Special Metals for information on available product forms.
Flat products: AMS 5608 Bar: AMS 5772
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