Hastelloy C276 is a nickel-chromium-molybdenum alloy containing tungsten, which is known for its corrosion resistance in various corrosive media.
The high content of molybdenum, it is resistant to localized corrosion such as pitting, the low carbon content, the precipitation of carbides during the welding process is minimized, so the resistance to intergranular corrosion of the heat-affected zone of the welded joint can be maintained.
C-276 alloy (00Cr16Ni60Mo16W4) came out in 1965. After 1970, it was produced by out-of-furnace refining process (AOD, VOD) to obtain ultra-low carbon (C≤0.02%) and high-purity alloy intrinsic quality.
In order to reduce the sensitivity and brittleness of the intergranular corrosion of Hastelloy C alloy after welding and hot forming, to overcome the serious shortcomings of solid solution treatment after welding or hot forming of Hastelloy C alloy, except for low carbon content (C≤0.02 %), it also reduces the amount of silicon in the alloy to ≤0.08%.
Reducing the amount of carbon can reduce the amount of carbide precipitation in the alloy; reducing the content of silicon can reduce the amount of precipitation of the intermetallic phase in the alloy, thereby achieving the purpose of improving the alloy's intergranular corrosion resistance. At the same time, the plasticity, toughness and processing formability of the alloy have also been greatly improved.
Chemical Composition
The typical controlled chemical composition of C-276 alloy is shown in Table 1, which is characterized by low carbon and low silicon. The structural characteristics are the same as Hastelloy C alloy, except that the number of carbides and intermetallic phases in the alloy is reduced.
C-276 can reduce the pressure during welding due to its extremely low carbon and silicon content. Like other nickel alloys, it is ductile, easy to form and weld, and has excellent resistance to stress corrosion cracking in chloride-containing solutions (austenitic stainless steel is prone to such degradation).
With high chromium and molybdenum content, it can resist oxidizing and non-oxidizing acids, and has excellent resistance to pitting and crevice corrosion in the presence of chlorides and other halides. In addition, it has strong resistance to sulfide stress cracking and stress corrosion cracking in sour oilfield environment.