J. Mater. Sci. Technol. ›› 2021, Vol. 76: 95-103.DOI: 10.1016/j.jmst.2020.11.013

• Research article • Previous Articles     Next Articles

Effect of post heat-treatment on the microstructure and high-temperature oxidation behavior of precipitation hardened IN738LC superalloy fabricated by selective laser melting

Kyu-Sik Kima, Sangsun Yangb, Myeong-Se Kimc, Kee-Ahn Leea,*()   

  1. a Department of Materials Science and Engineering, Inha University, Incheon 22212, Republic of Korea
    b Korea Institute of Materials Science, Changwon, 51508, Republic of Korea
    c Auratech Co., Ltd., Seongnam, 13449, Republic of Korea
  • Received:2020-06-29 Revised:2020-09-24 Accepted:2020-09-29 Published:2021-06-20 Online:2020-11-06
  • Contact: Kee-Ahn Lee
  • About author:*E-mail address: keeahn@inha.ac.kr (K.-A. Lee).

Abstract:

The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior. The as-built microstructure showed fine cell and columnar structure due to high cooling rate. Ti element segregation was observed in inter-cell/inter-columnar area. After post heat-treatment, the initially-observed cell structure disappeared, instead bimodal Ni3(Al, Ti) particles formed. High temperature (1273 K and 1373 K) oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure. The as-built IN738LC fabricated via the selective laser melting process displayed oxidation resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process. Heat-treated SLM IN738LC, although had similar oxidation weight-gain values to those of the SLM as-built material at 1273 K, showed relatively better oxidation resistance at 1373 K. Bimodal Ni3(Al, Ti) precipitate formed in the post heat treatment changed the local chemical composition, thereby led to changes in alumina former/chromia former location and fraction on the alloy surface. It was concluded that in heat-treated IN738LC increased alumina former fraction was found, and this resulted in excellent oxidation resistance and relatively low weight-gain.

Key words: IN738LC, Selective laser melting, High temperature oxidation, Post heat-treatment, Oxidation mechanism