Nickel based super alloys is used mostly in aerospace application.

1. Ni-based Super alloys: Processing and its Application By SIDHESHWAR KUMAR (107MM024)

2. Contents Introduction Hardening Mechanism Manufacturing Applications Substitute References

3. Introduction What is Superalloy? A superalloyis a metallic alloy which can be used at high temperatures, often in excess of 0.7 Tm Alloying additions for solution strengthening is by addition of lower amount of W, Mo, Ta, Nb and for Precipitation hardening by addition of g and g’ formers like Ti, Al, & Nb.

4. Types of Super alloy Ni – Based Co – Based Fe-Ni – Based

5. Why Ni-Based alloys ????

6. Hardening Mechanism Solid Solution Strengthening Precipitation Hardening

7. Major phases in Nickel superalloys Gamma (g) Gamma Prime (g') Carbides Topologically Close-Packed Phases

8. Gamma (g) The continuous matrix (called gamma) is an face-centered-cubic(FCC) nickel-based austenitic phase that usually contains a high percentage of solid-solution elements such as Co, Cr, Mo, and W.

9. SEM micrograph of minor microstructural constituents of the alloy in the g matrix.

10. Gamma Prime (g') The primary strengthening phase in nickel-based superalloys is Ni3(Al,Ti), and is called gamma prime (g '). It is a coherently precipitating phase (i.e., the crystal planes of the precipitate are in registry with the gamma matrix) with an ordered FCC crystal structure.

12. Carbides Carbon, added at levels of 0.05-0.2%, combines with reactive elements such as titanium, tantalum, and hafnium to form carbides (e.g., TiC, TaC, or HfC). During heat treatment and service, these begin to decompose and form lower carbides such as M23C6 and M6C, which tend to form on the grain boundaries. These common carbides all have an fcc crystal structure. The general opinion is that in superalloys with grain boundaries, carbides are beneficial by increasing rupture strength at high tempeature.

13. Metal Carbides

14. Topologically Close-Packed Phases These are generally undesirable, brittle phases that can form during heat treatment or service. TCPs (Sigma, Mu, Laves, etc.) usually form as plates (which appear as needles on a single-plane microstructure). TCPs arepotentially damaging for two reasons: they tie up g and g ' strengthening elements in a non-useful form, thus reducing creep strength, and they can act as crack initiators because of their brittle nature.

15. The Shearing of γ' Precipitates A dislocation cutting a particle

16. During Incoherency

17. The investment shell for casting a turbochargerrotor. A view of the interior investment shows the smooth surface finish. The completed work piece of turbocharger rotor.

20. 100 000 hrs. creeplifetimeunder 100 MPaat750°C

21. Stable at service temperature

22. Forgeable & Weldable

23. Corrosion resistance

25. True stress–true strain flow curves for the Ni-based superalloy under different strain rates and temperatures: (a) 1050 °C, (b) 1100 °C, (c) 1140 °C, and (d) 1180 °C.

27. APPLICATIONS Nickel-based super alloys are widely used in load-bearing structures to the highest homologous temperature 0.9 Tm, or 90% of their melting point. Aerospace Turbine blades and jet/rocket engines Marine industry Submarines Nuclear reactors Heat exchanger tubing Industrial gas turbines

28. A jet engine (Rolls-Royce Trent 800) Intermediate pressure compressor (IPC), High pressure compressor (HPC), High pressure turbine (HPT), Intermediate pressure turbine (IPT), Low pressure turbine (LPT), and the pressure and temperature profiles along the engine.

29. Gas Turbine for marine propulsion

30. Pressurized water reactor vessel head

31. Gas Turbine at thermal power plants

32. Rocket Motor Engine

33. Turbine Blades (Jet Engine) Nickel-based superalloy, about 65% of gamma-prime precipitates in a polycrystalline gamma matrix.

34. Substitutes Carbon fiber-reinforced carbon FRP Materials Glass fibers Carbon fibers Kevlar fibers Novalac (Epoxy) Vinyl ester resins

35. References F. Zupani, T. Bonˇcina, G. Lojen, B. Markoli,S. Spai, Structure of the continuously cast Ni-based superalloy GMR 235, Journal of Materials Processing Technology 186 (2007) 200–206 DayongCai, LiangyinXiong, WenchangLiu, GuidongSun, Mei Yao, Development of processing maps for a Ni-based superalloy, Materials Characterization 58 (2007) 941–946 F. Zupanic, T. B oncina, A. Krizman, B. Markoli, S. Spaic, Microstructural constituents of the Ni-based superalloyGMR 235 in the as-cast condition, Scripta Materialia 46 (2002) 667–672 De-Guang Shang, Guo-Qin Sun, Jian-Hua Chen, NengCai, Chu-Liang Yan, Multiaxial fatigue behavior of Ni-based superalloyGH4169 at 650 ◦C, Materials Science and Engineering A 432 (2006) 231–238. Wei Zhao, Lin Liu, Structural characterization of Ni-based superalloy manufactured by plasmatransferred arc-assisted deposition, Surface & Coatings Technology 201 (2006) 1783–1787 Kai Song, Mark Aindow, Grain growth and particle pinning in a model Ni-based superalloy, Materials Science and Engineering A 479 (2008) 365–372.

36. Cont.... Li Liu, Ying Li, Fuhui Wang, Influence of nanocrystallization on passive behavior of Ni-based superalloy in acidic solutions, Electrochimica Acta 52 (2007) 2392–2400. L.R. Liu, T. Jina, N.R. Zhaoa, Z.H. Wang, X.F. Suna, H.R. Guana, Z.Q. Hua, Effect of carbon addition on the creep properties in a Ni-based single crystal superalloy, Materials Science and Engineering A 385 (2004) 105–112. Ying Wu, Toshio Narita, Oxidation behavior of the single crystal Ni-based superalloyat 900 °C in air and water vapor, Surface & Coatings Technology 202 (2007) 140–145. T.S. Sidhu, S. Prakash, R.D. Agrawal, Hot corrosion studies of HVOF sprayed Cr3C2–NiCr and Ni–20Cr coatings on nickel-based superalloy at 900 °C, Surface & Coatings Technology 201 (2006) 792–800. H. Murakami, H. Harada and H. K. D. H. Bhadeshia, Location of Atoms in Re and V Containing Multicomponent Ni-Base Single Crystal Superalloys, Applied Surface Science, Vol. 76/77, 1994, 177-183. S. Yoshitake, V. Narayan, H. Harada, H. K. D. H. Bhadeshia and D. J. C. MacKay, Estimation of the gamma and gamma' Lattice Parameters in Nickel-base Superalloys using Neural Network Analysis, ISIJ International, Vol. 38, 1998, 495-502.

37. Cont… H. Fujii, D. J. C. MacKay, H. K. D. H. Bhadeshia, H. Harada and K. Nogi, Prediction of Creep Rupture Life in Nickel-Base Superalloys Using Bayesian Neural Networks, Journal of The Japan Insitute of Metals, Vol. 63, 1999, 905-911. F. Tancret, H. K. D. H. Bhadeshia, D. J. C. MacKay, T. Sourmail, M. Yescas, R. W. Evans, C. McAleese, L. Singh and T. Smeeton, Design of creep-resistant nickel-base superalloy for power plant applications, Materials Science and Technology, Parts 1-3, Vol. 19, 2003, 291-302. G.S. Hillier and H.K.D.H. Bhadeshia, The Homogenisation of Single-Crystal Superalloys, The Metals Society, London, 1984, pp. 183-187. H. Harada, A. Ishida, Y. Murakami, H. K. D. H. Bhadeshia and M. Yamazaki, Atom Probe Microanalysis of a Nickel-base Single Crystal Superalloy, Applied Surface Science, Vol. 67, 1993, 299-304.

38. Thank You “High temperature materials will be a major area of our research” Dr. V. K. Saraswat, Director-General, DRDO (Indian Science Congress, 2010)