Abstract
The investigation of high-entropy alloys (HEAs) has revealed many promising properties. HEAs with a high share of Al and Ti are suitable for the formation of lightweight materials. Investigations of the alloy system AlCoCrFeNiTi showed high strength, hardness, ductility, and wear resistance, which makes this special alloy interesting for surface engineering and particularly for thermal spray technology. In this study, the suitability of inert gas-atomised HEA powder for high-velocity-oxygen-fuel (HVOF) thermal spray is investigated. This process allows for high particle velocities and comparatively low process temperatures, resulting in dense coatings with a low oxidation. The microstructure and phase composition of the atomised powder and the HVOF coating were investigated, as well as the wear behaviour under various conditions. A multiphase microstructure was revealed for the powder and coating, whereas a chemically ordered bcc phase occurred as the main phase. The thermal spray process resulted in a slightly changed lattice parameter of the main phase and an additional phase. In comparison with a hard chrome-plated sample, an increase in wear resistance was achieved. Furthermore, no brittle behaviour occurred under abrasive load in the scratch test. The investigation of wear tracks showed only minor cracking and spallation under maximum load.
Highlights
High-entropy alloys (HEAs) are a new class of multicomponent alloy systems
The surface of the HVOF-sprayed coating only shows minor cracks and spallation in the area where the highest load was applied in progressive load scratch tests
Atomised powder of the equimolar compositionally complex alloys” (CCAs) system AlCoCrFeNiTi has been successfully applied Atomised powder of the equimolar CCA system AlCoCrFeNiTi has been successfully applied for a HVOF thermal spray process
Summary
High-entropy alloys (HEAs) are a new class of multicomponent alloy systems. They are typically composed of at least five elements with approximately equimolar amounts [1]. Several alloys have been investigated which showed the capability of forming multicomponent solid solutions with a simple fcc and bcc structure without brittle and intermetallic phases. Cantor et al proved the existence of one single fcc phase in the equimolar alloy CoCrFeMnNi [2]. Many previous investigations have shown that most alloy systems are composed of several phases, partially including complex phases. The term “compositionally complex alloys” (CCAs) was introduced for alloys which consist of at least two phases [6]
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