Microstructure Evolution of FeNiCoCrAl1.3Mo0.5 High Entropy Alloy during Powder Preparation, Laser Powder Bed Fusion, and Microplasma Spraying.

Anton Semikolenov,Olga Klimova-Korsmik,Pavel Kuznetsov,Tatyana Larionova,Ilya Kobykhno,Oleg Tolochko,Svetlana Shalnova,Viktor Klinkov,Tatyana Bobkova

doi:10.3390/ma14247870

Abstract

In the present study, powder of FeCoCrNiMo0.5Al1.3 HEA was manufactured by gas atomization process, and then used for laser powder bed fusion (L-PBF) and microplasma spraying (MPS) technologies. The processes of phase composition and microstructure transformation during above mentioned processes and subsequent heat treatment were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and differential thermal analysis (DTA) methods. It was found that gas atomization leads to a formation of dendrites of body centered cubic (BCC) supersaturated solid solution with insignificant Mo-rich segregations on the peripheries of the dendrites. Annealing leads to an increase of element segregations till to decomposition of the BCC solid solution and formation of σ-phase and B2 phase. Microstructure and phase composition of L-PBF sample are very similar to those of the powder. The MPS coating has a little fraction of face centered cubic (FCC) phase because of Al oxidation during spraying and formation of regions depleted in Al, in which FCC structure becomes more stable. Maximum hardness (950 HV) is achieved in the powder and L-PBF samples after annealing at 600 °C. Elastic modulus of the L-PBF sample, determined by nanoindentation, is 165 GPa, that is 12% lower than that of the cast alloy (186 GPa).

Highlights

Multicomponent alloys with high entropy began being studied in 2004 [1,2] and, until now, the amount of work devoted to high entropy alloys (HEA) continues to grow [3,4].Even though the idea of HEA implied one-phase multicomponent solid solution alloys when it first arose, nowadays the concept of HEA includes a wide spectrum of multi-phase multicomponent alloys [5]
The powder of FeCoCrNiMo0.5 Al1.3 HEA was synthesized via gas atomization and used for laser powder bed fusion and microplasma spraying processes
FeCoCrNiMo0.5 Al1.3 in equilibrium state consists of B2 and σ-phase

Summary

Introduction

Multicomponent alloys with high entropy began being studied in 2004 [1,2] and, until now, the amount of work devoted to high entropy alloys (HEA) continues to grow [3,4].Even though the idea of HEA implied one-phase multicomponent solid solution alloys when it first arose, nowadays the concept of HEA includes a wide spectrum of multi-phase multicomponent alloys [5]. The problem of structure and phase stability becomes especially acute when it concerns the alloys produced in non-equilibrium conditions. Raw powders should have spherical shape and narrow size distribution with an average size of 20–80 μm (depending on the method used). From this point of view, gas atomization can be considered the most appropriate powder-manufacturing route [25]. Gas atomization as well as additive and thermal spray techniques imply superfast cooling of molten metal, which results in a highly non-equilibrium structure. Structure evolution in HEA, especially those produced by superfast cooling of molten metal, is of great interest and importance

Methods

Results

Conclusion