Strengthening of Hastelloy alloys for performance in challenging environments

High nickel corrosion resistant alloys are called as Hastelloy grades. Hastelloy alloys are not just high strength materials in fact many of them keep such as high level of their room temperature strength at very high temperatures that structural applications at high temperatures are not atypical. Their strengths are variable depending on chemistry and form however normally these alloys have tensile strengths about 100,000 psi and yield strengths of about 50,000 psi. They are used basically for applications need outstanding corrosion resistance. Modification of Hastelloy wire is performed by the fabrication by forming and welding.

Hastelloy alloy B is significant for its exceptionally high resistance to all concentrations of hydrochloric acid at temperatures up to the boiling point. It is also resistant to other non-oxidizing acids and salts and has significant high temperature properties in that it keeps over 2/3^rd of its room temperature strength at 1600oF in oxidizing conditions. It can be used at high temperatures in reducing atmospheres. It should not be used for firmly oxidizing acids or salts.

Hastelloy alloy C has an excellent resistance to oxidizing solutions, particularly those containing chlorides, and hypochlorite solutions and moist chlorine. It prevents nitric, hydrochloric and sulfuric acids at average temperatures, has outstanding resistance to diverse corrosive organic acids and salts and is resistant to oxidizing and reducing conditions up to 2000oF. It should not be used above 120oF in nitric and hydrochloric acid and salt combinations.

Hastelloy X as outstanding strength and oxidation resistance up to 2200oF and is significant for many industrial furnace applications for its resistance to oxidizing, neutral and carburizing atmospheres. It has major applications in aircraft components like jet engine tail-pipes, after-burners, turbines, blades and vanes.

The line of demarcation between heat resistant alloys and super alloys is rather tenuous as indefinite as the dividing line between ferrous and nonferrous. Single phase alloys like Nichrome and Inconel alloy 600 are weak above 1250oF however their high temperature strength and resistance to creep are enhanced by the introduction of stable, hard phase or phases i.e. precipitated carbides or intermetallic compounds. Most of the high nickel super alloys are of the Aluminum-Titanium age-hardenable type. Chromium offers oxidation resistance along with auxiliary strengthening. Columbium, molybdenum, tungsten and tantalum are usually present to provide solid solution reinforcing of the matrix. The major part of the strengthening at high temperatures, is because of the precipitation of the Ni3(Al, Ti) compound, normally designated gamma prime phase. Precipitation hardening significantly  improves the stress-rupture properties of some nickel base alloys.