The matrix in the solid phase provides great strength and toughness over a wide range of conditions. The microstructure is face-centred cubic in structure. It can be conveniently used from cryogenic temperatures to temperatures as high as 1100°C retaining its mechanical properties. The chemical composition also contributes to its exceptional corrosion resistance.
- Nickel exceptionally resists chemical environments and various corrosion conditions.
- Chromium with the help of a protective oxide layer provides general corrosion resistance.
- Molybdenum gives localized corrosion resistance such as pitting and crevice corrosion.
- Columbium stabilizes the heat affected zones during processes, thus restricting inter-granular corrosion at grain boundaries.
Hence, the combination of these elements provide resistance to a wide range of corrosion environments even under oxidizing and carburizing conditions. The versatility of the alloy under various conditions enables the grade to be used in chemical processing applications having different pressures and temperatures. The alloy can also exceptionally resist chloride stress corrosion cracking. It also has great fatigue resistance, which makes it suitable to be used in dynamic applications. Applications involving thinner sections can use this alloy efficiently since it provides the required strength along with corrosion resistance and thermal properties. Also, the ease of fabrication helps the grade to be machined into required sections.
The alloy is compliant to be designed in high acceptable strength even at elevated temperatures. Annealing in the grade gives the alloy a very fine grain structure to be used up to 820°C, keeping its tensile and fatigue strength intact. The excellent ductility of the metal along with its impact strength gives the alloy freedom to be used in varied applications.
The impact strength of the grade is significantly retained even at cryogenic temperatures. At 30°C, the strength is about 70J, at -80°C the strength is about 60J, and at -200°C, the strength is about 45J. The grade might show some hardening during intermediate temperatures but with prolonged heating, carbide precipitation can be avoided at carbide-rich phases. Hot working, as well as forging, can be conveniently carried out under proper conditions - it is ideally performed around 980-1180°C. Hot working needs to be followed by annealing around the lower temperature range to obtain the fine grain structure. Cold working can also be done on the grade, however, since the grade tends to work harden, immense care needs to be taken. For intricate components, cold working needs to be done with intermediate annealing.
