View Sample Alloy Digest Data Sheet (PDF)Since 1952, Alloy Digest has been the leading reference for materials property data on metals and alloys used throughout the world. Featuring graphs, charts and tables, these sheets give facts and figures on composition or characterization, physical and mechanical properties, heat treatment, and machinability.ACI Type HK is an iron-chromium nickel alloy containing enough chromium to ensure good resistance to corrosion by hot gases, including sulfur-bearing gases, in both oxidizing or reducing conditions. Its high nickel content helps to make it one of the strongest heat-resistant casting alloy at temperatures above 1900 F. Accordingly, it is used for castings in stressed parts in structural applications up to 2100 F.