Influence of Cold Deformation and Annealing Process on Microstructure and Properties of Inconel Inconel 617B Alloy (Tech Center of Shanghai HY Industry Co., Ltd)
Inconel 617B alloy is a kind of Ni-Cr-Co-Mo superalloy mainly solid-solution strengthening obtained on the basis of Inconel 617 alloy. Al and Ti are added to the alloy to form a small amount of γ’ phase (4%~ 5%) precipitation strengthening, and there are a small amount of M6C phase and Ni2 (Cr, Mo) phase in the aged alloy. Because the alloy has excellent high-temperature durability and high-temperature oxidation resistance, it has been used as an advanced ultra-supercritical thermal power station at 700 °C Candidate materials for medium boiler superheaters, reheaters, headers and main steam piping. The research on this alloy mainly focuses on high-temperature structural stability, steam oxidation and corrosion resistance, and there are few researches on cold working and heat treatment. Researchers have studied the effects of cold rolling and annealing processes on the microstructure and mechanical properties of alloy pipes through experiments and theoretical calculations.
The experimental material is Inconel 617B alloy smelted by vacuum induction furnace smelting plus atmosphere protection electroslag remelting double process. Tube blanks are cold-rolled into tubes according to the deformation amount of 9% to 58%. Metallographic samples and mechanical test samples were cut from the cold-rolled pipe, and annealed at different temperatures and times in a box-type heat treatment furnace. The method is water cooling.
After the heat-treated sample was ground and polished, it was electrolyzed with 10% oxalic acid solution at a voltage of 5V, and the microstructure of the alloy was observed and analyzed through a LEICA-DMR optical microscope, and according to GB/T6394-2002 “Measurement Method for Average Grain Size of Metals” 》, using the straight line intercept method to count the average grain size. Tensile tests of standard tensile specimens before and after heat treatment were carried out on a Z150/SN5A electronic material testing machine. The results showed that:
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As the amount of cold deformation increases, the grains are elongated along the maximum principal deformation direction, forming a strip-shaped deformation band; the tensile strength and yield strength of the alloy at room temperature increase, and the elongation to 1160°C, the tensile strength and yield strength of Inconel 617B alloy pipes decrease and the plasticity increases as the temperature increases; the strength and plasticity of the alloy do not change much when the temperature continues to increase.
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As the annealing temperature increases, the grain growth exponent η of the alloy first increases and then decreases. At 1080°C, the η value is between 0.1 and 0.2. When the temperature rises to 1120-1160°C, the η value suddenly increases to 0.5-0.6, and when it reaches 1200°C, the η value decreases to 0.3-0.4.decreases; the deformation amount reaches 9 %, the pipe plasticity is very sensitive to deformation hardening.
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As the annealing temperature increases, the grains of the alloy gradually grow, and when the annealing temperature reaches above 1160 °C, the grain growth rate increases significantly; the activation of the grain growth of the cold deformed alloy under different deformation amounts The energy Q is much larger than the self-diffusion activation energy of pure Ni. The Q value increases first and then decreases with the increase of deformation.
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When the annealing temperature increases from 1080°C
