Microstructure and wear behavior of laser clad interstitial CoCrFeNi high entropy alloy coating reinforced by carbon nanotubes

In this study, the effect and characteristics of the laser clad interstitial CoCrFeNi high entropy alloy coating reinforced with carbon nanotubes (CNTs) was investigated. 1.0 wt% of CNTs were added as the reinforcement. To prepare composite powders before cladding, the CNTs and pre-alloyed CoCrFeNi powders were mechanically mixed without ball milling treatment. As a result, the microstructure of the CNTs on powder surface was well protected from serious damage. The effects of the CNTs upon the microstructure and wear behavior of the produced interstitial CoCrFeNi-CNTs coating were evaluated. The results showed that the intergranular (Fe, Cr)7C3/alpha eutectics were found to fully precipitate in the clad CoCrFeNi-CNTs coating. The hardness of the CoCrFeNi-CNTs coating was enhanced by 42.2% compared with that of the CoCrFeNi coating. The wear property was positively correlated with the hardness. The wear rate of the CoCrFeNi-CNTs coating (2.18 x 10(-5) mm(3).N-1.m(- 1)) was significantly lower than that of the CoCrFeNi coating (10.54 x 10(-5) mm(3).N-1.m(- 1)). The enhancements of the wear property originated from the solution strengthening of carbon on grains and the precipitation strengthening of (Fe, Cr)(7)C-3 carbides on grain boundaries. In wear process, the lamellar (Fe, Cr)(7)C-3/alpha eutectics deposited on worn surface and eventually formed a carbide hardening layer structure and prevent severe wear on the CoCrFeNi-CNTs coating.

Automated summary

The effect of carbon nanotubes (CNTs) in reinforcing a laser clad interstitial CoCrFeNi high entropy alloy coating was investigated. The addition of CNTs enhanced the hardness and wear properties of the coating. The microstructure of the CNTs on the powder surface was well protected from damage, and the wear rate of the coating was significantly reduced. This improvement in wear performance was attributed to the solution strengthening and precipitation strengthening effects of carbon and carbides.