Hastelloy C-276

Basic Composition

Hastelloy C-276 is a nickel-chromium-molybdenum alloy containing tungsten, and its chemical composition includes the elements of nickel (Ni), chromium (Cr), molybdenum (Mo), and tungsten (W), with the approximate content of each element as follows:

Physical Properties

Density and melting point: density of 8.9g/cm³, melting point between 1325 - 1370 ℃.

Mechanical Properties

Minimum mechanical properties when tested at 20°C:

Tensile strength: 690MPa after solid solution treatment.

Yield strength: 283MPa.

Elongation: 40%.

Brinell hardness: HBS (specific values are not explicitly given, only relevant values under testing conditions are mentioned).

Forrosion resistance

Resistance under a variety of corrosive environments

To most corrosive media: excellent corrosion resistance to most corrosive media in oxidized and reduced states.

Pitting corrosion, crevice corrosion and stress corrosion resistance: excellent resistance to pitting corrosion, crevice corrosion and stress corrosion cracking performance, in high temperature, mixed with impurities of inorganic and organic acids (such as formic acid and acetic acid), seawater corrosion environment is particularly outstanding.

Specific substances corrosion resistance: can resist wet chlorine, hypochlorite and chlorine dioxide solution corrosion, the high concentration of chloride salt solution (such as ferric chloride and copper chloride) also has significant corrosion resistance. Can also adapt to the corrosive environment in the low temperature and medium temperature hydrochloric acid, nearly three decades, in the chemical industry, petrochemical, flue gas desulfurization, pulp and paper, environmental protection and other industrial areas have considerable application, suitable for a variety of chemical process industries containing oxidizing and reducing media, in these harsh corrosive environments are widely used.

Thermal processing performance

Thermal processing temperature range: 1200 ℃ - 950 ℃, cooling mode for water-cooled or fast air cooling. In terms of hot processing fuel, the lower the sulfur content in the fuel, the better, for example, the sulfur content in natural gas should be less than 0.1%, and the sulfur content in heavy oil should be less than 0.5%.

Welding performance

Welding characteristics: Hastelloy C - 276 alloy has a face-centered cubic lattice structure, its matrix is a face-centered cubic lattice of solid solution, compared with the welding of carbon steel, has a low depth of fusion. Different choices of welding methods and bevel shapes will form different solidification organizations of the weld metal, thus affecting the depth of fusion and fusion of the weld.

Factors affecting welding:

Elemental segregation problems: sulfur, phosphorus and nickel can form eutectic segregation of the weld metal grain boundaries; aluminum and titanium to promote the formation of oxide film on the weld surface, the formation of isolated blocks and slag points; silicon and lead will lead to nickel alloys with hot brittle cracks; high carbon content will form a continuous intergranular compounds grain boundary film, making the alloy brittle, but also the formation of carbon and boride eutectic may also be generated under the action of stress will cause cracks, so the total amount of sulfur, phosphorus and other elements must be Controlled at a low level.

Stress and cracks: welding pool solidification process, metal contraction tensile stress generated by pulling the low melting point of the eutectic liquid film on the grain boundary, the formation of crystal cracks. The metal expands during high-temperature molten welding, and if there are additional stresses, uneven heating temperatures, and high line energies during weld shaping, it is easy to generate stresses that affect the quality of weld shaping. However, the alloy is suitable for welding by any conventional welding process, such as tungsten electrode inert gas shielded welding, plasma arc welding, manual argon arc welding, metal-pole inert gas shielded welding, fusion-pole inert gas shielded welding.

Forging performance

Problems in forging: Hastelloy C - 276 alloy electroslag ingot cast state organization of Mo, W elemental segregation, austenite grain boundaries at the presence of a large number of μ precipitation phase, which is the main cause of electroslag ingot forging cracking. The μ phase is a compound formed by W, M elements and other elements of group VI and Fe and other elements of group VIII, the precipitation phase is brittle, dislocations around the accumulation of plugs easily lead to cracks prematurely, the thermoplasticity of the material has a negative impact.

Solution: With the homogenization of heating temperature and insulation time extension, the alloy organization of dendritic precipitation gradually reduce. For example, electroslag ingot by 1170°C insulation 10h after air cooling, the segregation all disappear, forging effect is good, greatly improving the rate of material.