Titanium – Combines with carbon to reduce susceptibility to intergranular corrosion due to chromium
carbide precipitation resulting from heat treatments, and enhances age hardening.

Niobium (Columbium) – Combines with carbon to reduce susceptibility to intergranular corrosion due to chromium carbide precipitation resulting from heat treatments, improves resistance to pitting and crevice corrosion, and increases high temperature strength.

Tungsten – Improves resistance to reducing acids and to localized corrosion, and enhances both strength and weldability.

Nitrogen – Enhances metallurgical stability, improves pitting and crevice corrosion resistance, and increases strength.

Cobalt – Provides increased high-temperature strength, and resistance to carburization and sulfidation.

Many of these alloying elements can be combined with nickel in single phase solid solutions over a broad composition range to provide alloys with useful corrosion resistance in a wide variety of environments. These alloys, in turn, provide useful engineering properties in the fully annealed condition without fear of deleterious metallurgical changes resulting from fabrication or thermal processing. Many of the high-nickel alloys can be strengthened by solid solution hardening, carbide precipitation, precipitation (age) hardening and by dispersion strengthened powder metallurgy.

Reference Paper: High-Performance Alloys for Resistance to Aqueous Corrosion (Special Metals Corporation)