HAYNES® NS-163® alloy was developed by Haynes International Inc. for high-temperature structural applications with a dual manufacturing approach in mind: the fabrication of components in the readily weldable and formable mill-annealed condition, and their subsequent strengthening by means of a gas nitriding process. The alloy was designed to be conducive to dispersion strengthening by virtue of the formation of internal Ti- and Nb-rich nitrides. Since this process is diffusion-controlled, component section thicknesses are presently limited to approximately 2.0 mm (0.080″). The paper presents key parameters of the devised commercial nitridation process and the resulting microstructures and mechanical properties of sheet samples, which originated from a production-scale heat. Oxidation resistance and the need for coatings at temperatures exceeding 980°C (1800°F) are addressed as well. It is shown that this new alloy has the potential to fill the gap between today’s strongest solid-solution strengthened alloys and the oxide-dispersion strengthened mechanically alloyed materials.

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