Experimental Study and Molecular Dynamics Simulation of Laser Coated FeCoCrNiMn_x High Entropy Alloy Coating

In this study, three mixed powder systems comprising of FeCoCrNiMn₀, FeCoCrNiMn_0.25 and FeCoCrNiMn_0.5 were prepared by adding varying amounts of Mn into the classic high-entropy alloy system of FeCoCrNi. Subsequently, the three high-entropy alloy coatings were laser-clad onto Q235 steel. The micro-structure and evolution of the coating were thoroughly analyzed using X-ray diffraction, scanning electron microscope, energy-dispersion spectroscopy and other testing and analysis techniques. This paper focused on the tribological properties of the coated surface in terms of performance. The high-temperature friction and wear tester was used to perform ball-disk wear tests at room temperature to examine its anti-friction and wear-resistant qualities. The friction and wear process of FeCoCrNiMn_0.5 coating was simulated through the use of molecular dynamics simulation software and the results were then compared with test results. Furthermore, the wear process and behavior mechanism of the surface coating was further investigated by characterizing the work hardening and morphology of the damaged surface. The micro-structure and micro-structure evolution of the coating were analyzed in detail by means of XRD, SEM, EDS and other analysis and testing methods. In terms of performance, this paper mainly aimed at the tribological properties of the coating surface, and used the high-temperature friction and wear tester to conduct ball-disk wear tests at room temperature to characterize its anti-friction and wear resistance. The friction and wear process of FeCoCrNiMn_0.5 coating at room temperature was simulated by molecular dynamics simulation software, and the simulation results were compared with the test results. Furthermore, the wear process and behavior mechanism of the coating surface were further studied by characterizing the work hardening and surface damage morphology of the worn surface. The results showed that the FeCoCrNiMn_x high entropy alloy system achieved good metallurgical bonding and surface quality under the parameters of laser power 800 W, scanning speed of 4 mm/s and powder feeding rate of 14.5 g/min. In the structure phase, the coating formed FCC and BCC type solid solution after adding Mn element, and the solidification mode of grain growth was similar to that of traditional alloy, showing the transition of equiaxed crystal to dendrite and plane crystal, but due to the high cooling rate of laser cladding and the difference of physical and chemical characteristics between elements, there was still segregation of Mn elements. At room temperature, the FeCoCrNiMn_0.5 coating had the best friction reduction performance, with a friction coefficient of 0.66. The friction coefficient of other Mn high-entropy alloy coatings was only slightly decreased compared with the FeCoCrNi coating, but it was less than the Q235 steel substrate. The FeCoCrNiMn_0.5 coating had the lowest wear rate of 4.03×10⁻⁵ mm³/(N·m), which was 66.96% and 19.23% lower compared with Q235 steel substrate and FeCoCrNi coating, respectively. In terms of molecular dynamics simulation, the simulation results of FeCoCrNiMn high entropy alloy coating at room temperature also showed the same trend as the friction and wear test results.