Nickel Alloy-Alloy C-276

Alloy C276, with a high nickel contents, is immune to chloride-induced stress corrosion cracking. The high molybdenum and chromium contents allow the alloy to perform in oxidising, non-oxidising and mixed acids media, whilst exhibiting outstanding resistance to pitting and crevice corrosion attack. The addition of tungsten inhibits the development of pits. Finally, C276 is suitable for off-shore applications where hydrogen-sulphide(H2S) stress corrosion cracking resistance is essential.

In aggressive or corrosive environments when other alloys have failed, many companies have then turned to C276 alloy – one of the most corrosion resistant alloys on the market.

Industries where C276 is utilised are petrochemical and chemical processing, power generation, pharmaceutical, pulp and paper production and waste treatment to name a few.

Characteristic:

• Excellent corrosion resistance in reducing environments
• Exceptional resistance to strong solutions of oxidizing salts, such as ferric and cupric chlorides
• High nickel and molybdenum contents providing good corrosion resistance in reducing environments
• Low carbon content which minimizes grain-boundary carbide precipitation during welding to maintain resistance to corrosion in heat-affected zones of welded joints
• Resistance to localized corrosion such as pitting and stress-corrosion cracking
• One of few materials to withstand the corrosive effects of wet chlorine gas, hypochlorite and chlorine dioxide

Machining

Nickel and cobalt based alloys can be difficult to machinine. However, it should be emphasized that these alloys can be machined using conventional production methods at satisfactory rates. These alloys harden rapidly, generate high heat during cutting, weld to the cutting tool surface and offer high resistance to metal removal because of their high shear strengths. The following are key points which should be considered during machining operations:

• CAPACITY – Machine should be rigid and overpowered as much as possible.
• RIGIDITY – Work piece and tool should be held rigid. Minimize tool overhang.
• TOOL SHARPNESS – Make sure tools are sharp at all times. Change to sharpened tools at regular intervals rather than out of necessity. A 0.015 inch wear land is considered a dull tool.
• TOOLS – Use positive rake angle tools for most machining operations. Negative rake angle tools can be considered for intermittent cuts and heavy stock removal. Carbide-tipped tools are suggested for most
• applications. High speed tools can be used, with lower production rates, and are often recommended for intermittent cuts.
• POSITIVE CUTS – Use heavy, constant, feeds to maintain positive cutting action. If feed slows and the tool dwells in the cut, work hardening occurs, tool life deteriorates and close tolerances are impossible.
• LUBRICATION – lubricants are desirable. Soluble oils are recommended especially when using carbide tooling.