Tensile nickel-based alloys

Loss in tensile ductility is characterized by a decrease in elongation and reduction in area in an ordinary tensile test. It has been observed in steels (ferritic, martensitic, and austenitic), nickel-base alloys, aluminum alloys, and titanium alloys. The percentage loss in ductility depends on the hydrogen content of the alloy. 

Alloy 718 is a precipitation-hardened, nickel-based alloy, designed to display exceptionally high yield, tensile, and creep rupture properties up to 1300°F... 

Tables 10 and 11 list typical compositions of cast and wrought cobalt-base alloys, respectively. Stress—mpture properties of two wrought cobalt alloys, Haynes 188 and L-605, are compared to those of iron—nickel alloys ia Figure 10 (49). The cobalt alloys generally are inferior ia strength to the strongest cast nickel-base superaHoys. Tensile strengths at low and iatermediate temperatures are particularly deficient for the cobalt alloys.

Fig. 2.1 Elevated-temperature tensile properties for select nickel- and cobalt-base alloys. Source Ref 35, 37...

Not all metal.s and alloys can be persuaded to fracture in an intergranular manner by impact at low temperature. However, a whole group of metals and alloys will fracture in that mode if they are first embrittled by charging with hydrogen. Some will then fracture intergranularly by impact, but others require to be fractured by a slow tensile pull. This group includes the au.stenitic stainless steels [4], nickel [12], the nickel-base superalloys [14] and nickel aluminum alloys [45]. 

Subsequent to the issuance of Reference 15- 2, a tensile and creep strength database for another Nickel-base superalloy, Haynes 230, was obtained by NRPCT from commercial source. Primary stress limits similar to those developed for Alloy 617 had been developed in Reference 15-3 for Haynes 230. 

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