Phase Diagram Simulation and Investigation of Microstructure of Ni-Based Alloys

Abstract:

To develop proper Ni-based alloys for high-temperature vitriol pump which is submitted the corrosion of vitriol and rush of liquid with solid particles, the equilibrium phase diagrams of some Ni-Cr-Fe-C-Mo-Si-Cu alloys were calculated by software Thermo-Calc. Based on the simulation results and the mechanism of sigma phase precipitation strengthening, the chemical composition of a new Ni-based alloy was proposed. The alloy was casted and treated by solid solution at 1373K+2h, followed cooling to 1323K and quenching in water at room temperature, then strengthened by ageing respectively at 973K, 1023K, 1073K, 1123K for 4h. It was investigated the phases by XRD, the microstructures by OM and SEM. The proposed alloy consists of g, s and M23C6 from 1073K to 1273K. The most amount of s phase is up to 12.45 % (mass) at 1023K, it decreases with the augment of equilibrium temperature. s phase disappears above 1323K. The amount of s phase is enough in alloy to supply good precipitation hardening at a large temperature range. Experimental results were compared with the results of phase diagram simulation by Thermo-Calc. The alloy can be effectively strengthened by sigma phase precipitation at the temperature from 1023K to 1073K. Experimental results verified the validity of phase diagram simulation.

• Periodical: Advanced Materials Research (Volumes 634-638)
• Pages: 1826-1830
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.634-638.1826
• Online since: January 2013
• Authors: Zhan Ping Zhang, Yu Hong Qi, Min Feng
• Keywords: Aging, Ni-Based Alloy, Phase Diagram Simulation, Precipitation Strengthening, Vitriol Pump

References

[1] Yamashita T, Okuda K, Obara T. Application of thermo-calc to the developments of high-performance steels basic and applied research: Section I. Journal of Phase Equilibria, 20(3)(1999) 231-237

DOI: 10.1361/105497199770335767

[2] Kraft T, Exner H E. Restricted equilibrium phase diagram of nickel rich corner of quaternary system Ni-Cr-Fe-Mo, Materials Science and Technology, 14 (5)(1998)

DOI: 10.1179/mst.1998.14.5.377

[3] Saunders N. Phase diagram calculations for Ni-based superalloys, R.D. Kissinger et al Superalloys 1996. TMS, Warrendale, (1996)101

DOI: 10.7449/1996/superalloys_1996_101_110

[4] Zheng Yu-Gui, Yao Zhi-Ming, Y.S. Zhang, et al., Erosion-corrosion synergism and erosion-corrosion resistant alloy development, Acta metallurgica sinica, 36(1)(2000)51-54 (in Chinese)

[5] Guo Nin, Qin Zi-Rui, Study on the microstructure and corrosion behavior of a new type cast alloy by AFM, Corrosion & protection, 20(3)(1999)108-113(in Chinese)