Hastelloy C276 heat treatment and production, C276 and cladding process
Hastelloy C276 Overview:
Hastelloy C-276 alloy is a tungsten-containing nickel-chromium-molybdenum alloy with extremely low silicon-carbon content and is considered a universal corrosion-resistant alloy. Mainly resistant to wet chlorine, various oxidizing chlorides, chloride salt solutions, sulfuric acid and oxidizing salts, and has good corrosion resistance in low and medium temperature hydrochloric acid. Therefore, in the past thirty years, it has been widely used in harsh corrosive environments, such as chemical industry, petrochemical industry, flue gas desulfurization, pulp and paper making, environmental protection and other industrial fields.
Hastelloy C276 heat treatment and production:
thermoforming
Hastelloy C-276 alloy is hot formed and should be immediately annealed at 950 to 1200°C and subsequently rapidly cooled in water or air. It is recommended to perform heat treatment after heat processing. When heating, the alloy should be placed in a furnace that has been heated to the target value.
cold forming
The alloy should be in the annealed condition to facilitate cold working. C-276 has significantly higher cold strength compared to austenitic stainless steels. The formability is better than that of widely used austenitic stainless steel. In addition, this material works harden much faster than ordinary stainless steel, so mid-process annealing is required during extensive cold forming processes.
Descaling and pickling
C-276's oxides and discoloration near welds are more adhesive than stainless steel. It is recommended to use a very fine abrasive belt or disc for grinding. Care should be taken to prevent discoloration. Before pickling in a mixture of saltpeter and hydrofluoric acid, the oxide layer should be broken down and ground by sandblasting or fine grinding, or treated in a molten salt bath. The corrosion conditions of the pickling tanks used should be carefully monitored, especially concentration and temperature.
Machining
C-276 should be machined under heat treated conditions. Since the tendency to work hardening is significantly increased compared to austenitic stainless steels, the tool should always be engaged at lower cutting speeds when feed rates are not too high. Cut below the previously created strain-hardened zone using an appropriate cutting depth. By using a large number of heat exchangers to achieve optimal heat dissipation, the most suitable water-based lubricant for the machining process has a considerable impact on the stable machining process.
Hastelloy C-276 application areas:
Paper and pulp industry, e.g. for digestion and bleaching tanks
Scrubbers, agitators and wet ventilators in flue gas desulfurization systems
Sour gas application equipment and components
Acetic acid production reactor
Sulfuric acid cooler
Production and processing of contaminated phosphoric acid
Fluid chemical pumps, fluorine chemicals, etc.
Hastelloy C276 corrosion resistance:
① In both oxidizing and reducing atmospheres, it has excellent corrosion resistance to most corrosive media.
②Excellent resistance to pitting corrosion, crevice corrosion and stress corrosion. The higher Mo and Cr content make the alloy resistant to chloride ion corrosion, and the W element further improves the corrosion resistance. At the same time, Hastelloy C-276 alloy is one of the only materials resistant to corrosion by moist chlorine, hypochlorite and chlorine dioxide solutions, and is resistant to high-concentration chloride solutions such as ferric chloride and copper chloride. Remarkable corrosion resistance. It is suitable for sulfuric acid solutions of various concentrations and is one of the few materials that can be used in hot concentrated sulfuric acid solutions.
Hastelloy C276 and laser cladding technology:
Hastelloy C276 is a Ni-Mo-Cr-W series nickel-based alloy with high strength, toughness and corrosion resistance, especially in media such as wet chlorine and chloride salt solutions. Therefore, domestic and foreign scholars have conducted relevant research on the preparation of C276 coating. Supersonic flame spraying technology is used to prepare a C276 cladding layer on the surface of 316L stainless steel. The cladding layer has a layered structure and is dense. Its microhardness and wear resistance are significantly higher than those of the base material. The C276 coating is laser cladded on the gun barrel steel. The coating is well formed and the corrosion resistance is on the same level as the chromium plating coating.
Research shows that C276 coating has good compatibility with steel and can significantly improve the wear resistance and corrosion resistance of the steel surface. At present, C276 Hastelloy coatings prepared by domestic and foreign counterparts are generally used on steel.
