Regular Article

Oxidation and hot corrosion behavior of a directionally solidified W richen cobalt-based superalloy

¹ School of Mechanical Engineering and Automation, Shenyang Institute of Technology, Fushun 113122, PR China
² Liaoning Key Laboratory of Information Physics Fusion and Intelligent Manufacturing for CNC Machine, Shenyang Institute of Technology, Fushun 113122, PR China

^* e-mail: zhouyuebo760309@163.com

Received: 29 October 2020
Accepted: 19 April 2021

Abstract

In this study, isothermal and hot corrosion in molten 75 mass% Na₂SO₄+25 mass% NaCl at 900 °C was carried out on an W richen Co-based directionally solidified Co-27.53Cr-9.85W-10.29Ni-0.75Al superalloy. For comparison, K38G with composition of 16.34Cr-4Al-1.77Mo-3.81Ti-2.66W-8.38Co were also conducted under same condition. Isothermal oxidation indicates that Co-based superalloy forms a Co-oxide dispersion chromia scale. However, K38G forms a purer chromia scale due to higher weight percentage ratio of Cr to Al. Under molten Na₂SO₄-NaCl salts, the defects in Ni/Co oxide dispersion chromia layer make it feasible that the molten salt can penetrates along grain boundaries into the internal interface to form internal sulfides, which causes the spallation of scales and significantly decreases its hot corrosion resistance.