Incoloy 800 H is an iron-nickel-chromium alloy having the similar basic composition as Incoloy 800, with significantly higher creep rupture strength. The higher strength results from close control of carbon, aluminum and titanium contents in conjunction with a high temp anneal. The 800H modification was to ensure control of carbon (0.05 to 0.10%) and grain size to (>ASTM 5) to maximize stress rupture properties. Incoloy 800 H has further modifications to the combined titanium and aluminum levels (0.85 to 1.2%) to ensure optimum high temperature properties. The alloy is dual certified and combines the properties of both forms.
The chemical balance permits the alloy to exhibit great resistance to carburization, oxidation and nitriding atmospheres. 800HT will not become embrittled even after extended periods of usage in the 1200-1600oF range, a range where most stainless steels become brittle.
Conventional machining procedures used for iron based alloys may be used. This alloy does work-harden during machining and has higher strength, not typical of steels. Heavy duty machining equipment and tooling should be used to reduce chatter or work-hardening of the alloy ahead of the cutting. Any commercial coolant may be used in the machining operations. Water-base coolants are favored for high speed operations such as turning, grinding, or milling. Heavy lubricants are best for drilling, tapping, broaching or boring
Excellent cold forming characteristics typically associated with the nickel-chromium alloys are exhibited with 800HT. When cold formed extensively the grain size yields a visibly undulated surface called “orange peel”. 800HT can be welded by the common techniques used in stainless steels.