Article Periodicals » Materials Evaluation » Article
Replica Metallography: An NDT Technique for Condition Assessment of Gas Turbine Components

There is a need to evaluate the microstructure of the serviced gas turbine components without destroying or cutting samples from the components. The nondestructive methods and techniques, such as penetrant testing (PT), eddy current testing, and radiographic testing (RT), cannot determine the cracks along the grain boundaries in the gas turbine components. Conventional laboratory metallography calls for sampling, but with the replica metallography technique, the microstructure of the components can be evaluated nondestructively. Replica metallography is an effective nondestructive technique that is used to assess the condition of the high temperature components. Replica evaluation is performed using a light optical microscope (LOM) and a scanning electron microscope (SEM). Replica metallography has gained wide acceptance in the utility industry since it is cost effective, quick, and reliable. Condition assessment and life extension programs for rotating and non-rotating gas turbine components are popular and widely practiced in the industry. Replica metallography is one of the vital techniques used for assessment of gas turbine components. Gas turbine components experience various types of damage, such as creep, fatigue, and high/low temperature corrosion. These damages are intrinsically reflected in the microstructure to some extent. The reliability, availability, and efficiency of the gas turbine operation are very often based on condition assessment and remaining life analysis. As a part of the incoming inspection of the gas turbine components, there is a need to examine the microstructure of the serviced gas turbine components such as turbine wheels, compressor wheels, combustion liners, and transition pieces nondestructively. The prime objective is to determine the condition of the components by evaluating the microstructure for continuation in service. Replica metallography technique was performed on the serviced gas turbine components. The microstructure was then evaluated using a light optical microscope and a scanning electron microscope. The replica technique details and significant test result findings of replica metallography are presented and discussed in this paper.

References

ASM Handbook Volume 9: Metallography and Microstructures, ed. George F. Vander Voort, ASM International, Materials Park, Ohio, 2004, pp. 836–837.

ASTM E1351-01 (2006) – Standard Practice for Production and Evaluation of Field Metallographic Replicas, ASTM  International, West Conshohocken, Pennsylvania. 

Brown, J.A., R. Freer, and A.T. Rowley, “Reconditioning of Gas Turbine Components by Heat Treatment,” Journal of Engineering for Gas Turbines and Power, Vol. 123, No. 1, 2000, pp. 57–61.

Daga, R., Bandyopadhyay, G., Samal, M.K., Dutta, B.K., Mohindru, A.K., “Consumed Creep Life Fraction Assessment of Critical Locations of an In-Service Super Heater Outlet Header Under Surveillance Programme,” Transactions of  the Indian Institute of Metals, Vol. 63, No. 2, 2010, pp. 423-429.

Davies, P.W. and J.P. Dennison, “The Use of Heat-Treatment to Recover the Creep Properties of Nimonic 115 After High-Temperature Creep,” Metal Science, Vol. 9, No. 1, 1975, pp. 319–323.

Dennison, J.P. and B. Wilshire, “Mechanism of Improving Creep Rupture Lives by Heat Treatment,” The Physical Metallurgy of Fracture: Fourth International Conference on Fracture, ed. D.M.R. Taplin, University of Waterloo, Canada, 1977, pp. 635–639.

He, Yinsheng, Jiling Dong, Woosung Choi, Jinesung Jung, and Keesam Shin, “An Improved Non-Destructive Repli-cation Metallography Method for Investigation of the Precipitates in Cr-Mo-V Turbine Steel,” Surface and Interface Analysis, Vol. 44, Nos. 11–12, 2012, pp. 1411-1414.

Krongtong, V., P. Tuengsook, W. Homkrajai, E. Nisaratanaporn, and P. Wangyao, “The Effect of Re-heat Treatments on Microstructural Restoration in Cast Nickel Superalloy Turbine Blade, GTD-111,” Acta Metallurgica Slovaca, Vol. 11, No. 2, 2005, pp. 171–182. 

Liburdi, Joseph, Paul Lowden, Douglas Nagy, Tiberius Rusan De Priamus, and Stephanie Shaw,, “Practical Experience With the Development of  Superalloy Rejuvenation,” Paper No. GT2009-59444, ASME Turbo Expo 2009: Power for Land, Sea, and Air, Orlando, Florida, 2009, pp. 819–827.

Lindblom, Y., “Refurbishing Superalloy Components for Gas Turbines,”  Materials Science and Technology, Vol. 1, No. 8, 1985, pp. 636–641.

Prasad, C.R. and Kulvir Singh, “Remaining Life Assessment (RLA) of Gas Based Units– Case Studies ,” Transactions of Indian Institute of Metals, 2010, Vol 63, No. 2, pp. 278–279.

Schilke, P.W., Advanced Gas Turbine Materials and Coatings, GER-3569G, GE Energy, 1995–2004, pp. 1–2.

Seyed  Abdolkarim Sajjadi, Said Nategh, and Roderick I. 

L. Guthrie, “Study of Microstructure and Mechanical Prop-erties of High Performance Ni-base Superalloy GTD-111,” Materials Science and Engineering A, Vol. 325, Nos. 1–2, 2002, pp. 484–489.

Shejale, G., “Metallurgical Evaluation and Condition Assessment of FSX 414 Nozzle Segments in Gas Turbines by Metallographic Methods,” Paper No. GT2010-22542, ASME Turbo Expo 2010: Power for Land, Sea, and Air, Glasgow, UK, 2010, pp. 969–977.

Shirzadi, A. and S. Jackson, eds. 2014. Structural Alloys for Power Plants,  A. Woodhead Publishing, Elsevier Ltd., Sawston, Cambridge, United Kingdom, 2014.

Vishwanathan, R. and A.C. Dolbec, “Life Assessment Tech-nology for Combustion Turbine Blades,” Journal of Engi-neering for Gas Turbines and Power, Vol 109, No. 1, 1987, pp. 115-123.

Viswanathan, R., 2006, Damage Mechanisms and Life Assessment of High-Temperature Components, ASM Interna-tional, Materials Park, Ohio, 2006.

Walter, Kurt and Wayne Greaves, “Life Assessment of Gas Turbine Components using Non-Destructive Inspection Techniques,” GT-373, International  Gas Turbine and Aero-engine Congress and Exhibition, Orlando, Florida, June 1997.  

Wortmann, J., “Improving Reliability and Life-time of Rejuve-nated Turbine Blades,” Materials Science and Technology, Vol. 1, No. 8, 1985, pp. 644–650.

Zangeneh, Sh., H. Farhangi, and H.R.Lashgari, “Rejuvena-tion of Degraded First Stage Gas Turbine Nozzle by Heat Treatment,” Journal of Alloys and Compounds, Vol. 497,  No. 1-2, 2010, pp. 360–368.

Metrics
Usage Shares
Total Views
103 Page Views
Total Shares
0 Tweets
103
0 PDF Downloads
0
0 Facebook Shares
Total Usage
103