ABSTRACT
Thermal fatigue produces fractures that are virtually identical to creep failures. If sustained maximum operating temperatures will create significant creep strain, the component is at risk of failure by stress rupture, typically associated with tertiary creep. In primary creep, the material plastically deforms while undergoing rapid work hardening. During secondary creep, grain boundary yielding produces local work hardening and the nucleation of grain boundary voids. Most designs for temperatures exceeding 1500°F must allow for creep and/or stress rupture. The procedure used to select materials of construction must include consideration of various forms of materials degradation, including electrolytic corrosion, high-temperature corrosion and stress corrosion cracking. Conventional stainless steels, both austenitic 300-series alloys and the straight chromium grades such as Types 405 and 410 Stainless Steel, can be subject to intergranular corrosion or cracking as a result of a phenomenon called sensitization.
