Microstructural Restoration by HIP and Heat Treatment Processes in Cast Nickel Based Superalloy, IN-738
Panyawat Wangyao, Gobboon Lothongkum, Viyaporn Krongtong, Weerasak Homkrajai and Nutthita Chuankrerk* Author for corresponding; e-mail address: nutthita.c@chula.ac.th
Volume: Vol.36 No.3 (SEPTEMBER 2009)
Research Article
DOI:
Received: 9 April 2009, Revised: -, Accepted: 7 May 2009, Published: -
Citation: Wangyao P., Lothongkum G., Krongtong V., Homkrajai W. and Chuankrerk N., Microstructural Restoration by HIP and Heat Treatment Processes in Cast Nickel Based Superalloy, IN-738, Chiang Mai Journal of Science, 2009; 36(3): 287-295.
Abstract
Inconel 738, as a cast nickel-based superalloy components for land-based gas turbine blades, utilized at elevated temperatures, expresses microstructural stability with excellent mechanical properties. In this study, the microstructural refurbishment by a hot isostatic pressing (HIP) and different heat treatment conditions after long-term service of the alloy was investigated. Although, the HIP temperature in the HIP process was high enough to act as solutioning treatment, it could not completely dissolve coarse γ' particles into the matrix, resulting in the residue particles. However, the next step, solutioning treatment, could dissolve these particles more in some extent depending on each solutioning temperature. The higher solutioning temperature provided the finer γ particles and new γ' precipitation after solutioning that could take place during primary aging. Secondary aging led to the growth of coarse and/or very fine γ' particles. All heat treatment conditions after HIP process provided much more uniform γ' morphology comparing to as-received microstructure.