CASE HISTORY—PEER-REVIEWED Condition Assessment Study of A-286 Alloy Gas Turbine Wheel Girish Shejale . Rajnish Garg . Garimella V. Subrahmanyam . Alexander Schnell Submitted: 9 June 2016 / Published online: 31 August 2016 Ó ASM International 2016 Abstract Life extension programs for rotating and non- rotating gas turbine components are popular and widely practiced in the industry. It is often possible to extend the life of the component beyond the design life through life assessment studies. The life assessment study generally includes a combination of nondestructive and destructive tests. Considering the life assessment approach, a Frame 5002 unit gas turbine wheel was examined nondestructively. The material of the turbine wheel is A-286, which is an iron- based super alloy. This turbine wheel has accumulated more than 200,000 service hours. The objective for nondestructive testing of this wheel was to check for any material degra- dation and any surface cracking in order to ensure extended service hours. The nondestructive tests included eddy cur- rent test, ultrasonic flaw detection, replica metallography, and portable hardness test. As such, no significant abnor- malities were detected in the nondestructive tests performed. The replica metallography revealed excessive carbide pre- cipitation. It was recommended to retire the turbine wheel from service. The significant test result findings of replica metallography are presented and discussed in this paper. Keywords Carbides Á Condition assessment Á Replica Á Microstructure Á Life extension Á Turbine wheel Introduction Life extension studies are popular among gas turbine users commonly used to extend the life of components after the design life. Life extension programs comprises primarily of various nondestructive tests, involving condition assess- ment. It may also call for destructive testing, if the component assessed through nondestructive testing is in question. Condition assessment primarily assesses the present condition of the gas turbine components by various nondestructive techniques [1]. The condition assessment of high-temperature components through various nonde- structive techniques assures reliability, availability of the components, or plants within stipulated amount of time. In situ metallography is one such technique which can determine any microstructural damages [2, 3]. In most utilities, the turbine manufacturer’s recom- mendations constitute the principal basis for replacement of components. These recommendations are often based on the manufacturers’ past experience. The methodologies and criteria by which they are arrived at are unclear to the utilities. Gas turbine users would like the capability for independent assessment of the conditions of their compo- nents. This concern has become increasingly serious as the cost of replacement parts has escalated [4]. Condition assessment study was performed on an A-286 turbine wheel from Frame 5002, gas turbine unit and was G. Shejale (&) Masaood John Brown, P.O. Box 11931, Dubai, United Arab Emirates e-mail: gshejale@mjbi.com R. Garg Á G. V. Subrahmanyam Department of Mechanical Engineering, University of Petroleum and Energy Studies, Dehradun, India R. Garg e-mail: rgarg@ddn.upes.ac.in G. V. Subrahmanyam e-mail: gvsubrahmanayam@ddn.upes.ac.in A. Schnell Schnell-Tech Limited, P.O. Box 8822, Dubai, United Arab Emirates e-mail: alex@schnell-tech.net 123 J Fail. Anal. and Preven. (2016) 16:712–717 DOI 10.1007/s11668-016-0154-6