Effect of Heat Treatments after HIP Process on Microstructure Refurbishment in Cast Nickel-Based Superalloy, IN-738
Keywords:Nickel base superalloy structure degradation Hot Isostatic Pressing (HIP), Rejuvenation, Re-heat treatment, Microstructural healing
The aim of this research work is to investigate the most convenient and practicable repair procedure, which could provide the appropriate microstructure characteristics in exposed turbine blades. The blades were cast from nickel-based superalloy IN-738 and were long-term exposed under conditions of land base gas turbine operation for 50,000 hours by EGAT of Thailand. The rejuvenation process includes the hot isostatic pressing (HIP) which is followed by a series of various heat treatment conditions involving either precipitation aging and or both solutioning and precipitation aging. The HIP was carried out at a pressure of 100 MPa for 5 hours at 1,200°C Then HIPed specimens were vacuum heat treated. The hot isostatic pressing could mostly heal any internal structural voids and cracks, which were generated during service. It was found that any microcrack was observed after the HIP process was exposed for 5 hours. However, microvoids were still found even after the HIP process but in very small amounts. Therefore, both the size and the amount of remained microvoids should be evaluated with respect considering both obtained virgin original material and after long-term exposed material. Furthermore, during solution treatment, coarse carbides and over-exposed gamma prime precipitates, which were formed and modified previously at the grain boundaries during service by the creep mechanism, are expected to the matrix. Then specimens were processed through a series of precipitation aging, which re-precipitates the strengthening phase to form the proper morphology in size and shape as well as distribution that is almost similar to the new one. Metallurgical examination of the microstructure had been performed by utilizing an optical microscope and a scanning electron microscope after hot isostatic pressing and heat treatment to evaluate the micro-defects elimination.
Zrnik, J., Strunz P., Vrchovinsky, V.,Muransky, O., Novy, Z. and Wiedenman, A. 2004. Mater.Sci. Eng. A 387-789 : 728-733.
Daleo, J. A., Ellison, H. A. and Boone, D.H. 2002. J. Eng. . Gas Turbines .Power. 124 (July) : 571-579.
Zrník, J., Horňak, P., Pinke, P., Žitňanský, M. 1996. Creep Fatigue Characteristics of Single Crystal Nickel Base Superalloy CMSX 3, Metals Alloys Technologies. (Kovine zlitine technologije), 3-4, Ljubljana, Slovenia. : 179 – 183.
Zrník, J., Wang, J.A., Yu, Y., Peijing, L. and Horňak, P. 1997. Influence of cycling frequency on cycling creep characteristics of nickel base single crystal superalloy. Mater. Sci. . Eng. A234-236 : 884 – 888.
Wangyao, P., Nisaratanaporn, E., Zrník, J., Vrchovinský, V., Horňak, P. 1997. High temperature properties of wrought nickel base superalloy in creep - fatigue conditions. J.Met. Mater. Miner. 7 (1) : 1 – 12.
Zrník, J., Wangyao, P., Vrchovinský, V., Horňak, P. and Mamuzič, I. 1997. Deformation behavior of Wrought Nickel Base Superalloy in Conditions of Thermomechanical Fatigue. Metalurgija (Metallurgy) 36 (4) : 225 – 228.
Zrník, J., Huňady, J., Horňak, P. 2002. Nickel Based Single Crystal Superalloy CM 186 – potential Material for Blades of Stationary Gas Turbine. Metalurgija (Metallurgy). 41 (3) : 232.
Zrník, J., Strunz, P., Horňak, P., Vrchovinský, V. and Wiedenmann, A. 2002 Microstructural changes in long-time thermally exposed Ni-base superalloy studied by SANS. Appl. Phys. A 74 : S1155-S1157.
Zrník , J., Semeňák, J., Wangyao, P., Vrchovinský, V., Horňak, P. 2003. The Analysis of Low Cycle Fatigue Behaviour in a Nickel Based Superalloy. J.Met. Mater. Miner. 12 (2) : 33 – 40.
Zrník, J., Jenčuš, P., Lukáš, P., Horňak, P., Wangyao, P.2004. Stress Evolution in Nickel Based Single Crystal Superalloy Subjected to Thermal Cycling, J. Met. Mater. Miner. 13 ( 2) :. 25 – 31.
Wangyao, P., Zrník, J., Nisaratanaporn, E., Vrchovinský, V., Horňak, P. 2004. The Study of Isothermal and Anisothermal Deformation Behaviors of Wrought Polycrystalline Nickel Based Superalloy. J.Met. Mater. Miner. 13 (2) : 55 – 63.
Zrník, J., Strunz, P., Vrchovinský, V., Muránsky, O., Horňak, P. and Wiedenmann, A. 2004. Creep deformation and microstructural examination of a prior thermally exposed nickel base superalloy. Key Eng. Mater. 274 - 276, : 925 – 930.
Jenčuš, P., Zrník, J., Lukáš, P. and Horňak P.2004. Thermal fatigue aspects in nickelbase single crystal superalloy. Acta Metall. Slovaca. 10 : 487 – 493.
Zrník, J., Strunz, P., Vrchovinský, V., Muránsky, O., Horňak, P. and Wiedenmann, A. 2004. Evaluation of structure stability in thermally exposed nickel base superalloy. Acta Metall. Slovaca. 10 : 448 – 453
Zrník, J., Semeňák, J., Horňak, P. and Vrchovinský, V. 2004. Lifetime behaviours of the wrought nickel base superalloy subjected to low cyclic fatigue with holds. Kovové Materiály – Metallic Materials. prijaté do tlače 15 : 12.
Sajjadi, S.A., Nategh, S., and Guthrie, R.I.L. 2002. Mate. Sci. Engi. A 325 : 484-489.
Nategh S. and Sajjadi S. A. 2003. Mater. Sci. Eng. A 339: 103-108.
Hoffelner, W., Kny, E., Stickler, R., and McCall, W. J. Z. 1979. Werktoff . 10 : 84.
Ojo, O. A., Richards, N. L. and Chaturvedi M. C. 2004. Scripta Materilia. 50 : 641-646
Sawaminathan, V. P., Cheruvu, N. S., Klien, J. M. and Robinson, W. M. 1998. The American Society of Mechanical Engineers (ASME) June.
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