Microstructure of Laser Re-Melted AlCoCrCuFeNi High Entropy Alloy Coatings Produced by Plasma Spraying

Tai Yue,Guanghui Meng,Xin Lin,Haiou Yang,Hui Xie

doi:10.3390/e15072833

Abstract

An AlCoCrCuFeNi high-entropy alloy (HEA) coating was fabricated on a pure magnesium substrate using a two-step method, involving plasma spray processing and laser re-melting. After laser re-melting, the microporosity present in the as-sprayed coating was eliminated, and a dense surface layer was obtained. The microstructure of the laser-remelted layer exhibits an epitaxial growth of columnar dendrites, which originate from the crystals of the spray coating. The presence of a continuous epitaxial growth of columnar HEA dendrites in the laser re-melted layer was analyzed based on the critical stability condition of a planar interface. The solidification of a columnar dendrite structure of the HEA alloy in the laser-remelted layer was analyzed based on the Kurz–Giovanola–Trivedi model and Hunt’s criterion, with modifications for a multi-component alloy.

Highlights

In recent years, much interest has been generated in applying magnesium alloys for stress-bearing applications in the automotive and aerospace industries [1,2]
This study focuses on the study of the microstructure of the laser re-melted high-entropy alloy (HEA) coatings produced by plasma spraying
The as-sprayed layer consists of flattened lamellae (Figure 2) with the presence of some micro-porosity (Figure 3), which are typical features resulting from plasma spray methods

Summary

Introduction

Much interest has been generated in applying magnesium alloys for stress-bearing applications in the automotive and aerospace industries [1,2]. Notwithstanding that protective coatings can be fabricated on Mg alloys using laser surface processing techniques [11], the main problems of the high chemical reactivity, the relatively low melting and boiling points of Mg alloys, and the formation of brittle intermetallic compounds in the coating cannot be overcome. Another common problem encountered in the laser cladding of a protective coating on Mg substrates is that significant dilution from the substrate often occurs, and this can adversely affect the corrosion resistance of the coating. This study focuses on the study of the microstructure of the laser re-melted HEA coatings produced by plasma spraying

Experimental Details

Microstructure and Epitaxial Growth

Columnar to Equiaxed Transition

Conclusions