Tribocorrosion Behavior of CoCrNi Medium Entropy Alloy in Simulated Seawater

Xian-Zong Wang,Haifeng Wang,Qing Zhou,Zhuobin Huang,Yanfei Wang

doi:10.3390/met12030401

Abstract

Understanding the fundamental behaviors of tribocorrosion for metals is critical for their possible application in seawater. For the recently emerging medium entropy alloys (MEAs), while mechanical wear and corrosion phenomena have been established, such experimental exploration is still lacking regarding the tribocorrosion behavior. In this work, the tribocorrosion behavior of CoCrNi MEA was investigated on a reciprocating sliding friction testing machine. Although a significant increase of current density formed due to sliding, CoCrNi exhibits superior passivity when compared with 316L and Inconel 600. In addition, the total tribocorrosion volume loss increases with positive shifting of the applied potential for CoCrNi. Specifically, the total material loss at an applied potential more positive than the pitting potential is one order in magnitude larger than that under pure mechanical wear, confirming the synergy between wear and corrosion. The generated pits on the worn surface became the preferred locations of wear and tear, leading to accelerated materials’ loss rate. Through detecting the morphologies of the contact surfaces, the features of abrasive wear, adhesive wear, delamination, and plastic deformation were revealed for CoCrNi during tribocorrosion at different potentials.

Highlights

High-entropy alloys (HEAs), as a class of newly superior-performance alloys, composed of five or more than five equiatomic or nearly equiatomic elements, are expected to be utilized at extreme elevated, cryogenic, strong corrosive conditions, due to their excellent structure stability, chemical inertness, and mechanical properties [1–6]
The open circuit potential (OCP) remained in the stable range, and the CoCrNi surface was passivated for 10 min before the sliding
OCP rapidly shifts negatively after the slide begins. This is due to the fact that the passive film covering the surface of CoCrNi is destroyed under external load after the friction begins, exposing the fresh metal to the solution and increasing the corrosion tendency of the material [25,26]

Summary

Introduction

High-entropy alloys (HEAs), as a class of newly superior-performance alloys, composed of five or more than five equiatomic or nearly equiatomic elements, are expected to be utilized at extreme elevated, cryogenic, strong corrosive conditions, due to their excellent structure stability, chemical inertness, and mechanical properties [1–6]. With further research, it has been found that medium-entropy alloys (MEAs) represented by CoCrNi have superior damage tolerance compared with CoCrFeNiMn HEAs [10,11]. Over the past few years, considerable attention has been dedicated to alloy development and an understanding of the monotonic corrosion or wear behavior of CoCrNi [14–17]. The development of MEAs possessing excellent tribocorrosion performance is vital for their wider applications. The deep research of tribocorrosion behavior of CoCrNi is desperately needed due to its significant impact on seawater application

Methods

Results

Conclusion