Enhancement mechanism of contact mechanical properties of laser powder bed fused FeNiCrCoAl0.5-X% ZrB2 coatings: experiments and molecular dynamics simulations

In this paper, experiments and molecular dynamics (MD) simulations are used to investigate the mechanisms that improve the contact mechanical properties of FeNiCrCoAl 0.5 -X% ZrB 2 coatings (X = 0, 10, 20, 30) prepared by laser powder bed fusion. Experimental results showed that the microhardness of coatings containing 30% ZrB 2 increased by 69.78% compared to the pure high-entropy alloy (HEA) coatings. When ZrB 2 is added to the coatings, more Laves phases, BCC phases, intermetallic compounds, columnar crystals or equiaxial crystals appear inside the coatings. The MD-based nanoindentation simulation revealed that the nanohardness and elastic modulus of the coating containing 30% ZrB 2 are increased by 74.50% and 18.92%, respectively, compared to the pure HEA coating. The strong stress-absorbing effect of ZrB 2 leads to a large number of new dislocations in the model. The barrier effect of ZrB 2 ceramic layer impedes the free expansion of highly strained atoms, as well as the free expansion and movement of dislocations, which results in a higher hardness and improved contact mechanical properties of the coating. Owing to the limited reduction in the width of free stacking faults, the model with 30% ZrB 2 content at full indentation has lower stacking fault energy and higher strain hardening ability, resulting in improved contact mechanical properties. • Contact properties of HEA-ZrB 2 coatings are studied by experiment & MD simulation. • Nanohardness and elastic modulus of FeNiCrCoAl 0.5 -30% ZrB 2 coating are highest. • Grain refining, stress absorption, and barrier effect of ZrB 2 strengthen the coating. • ZrB 2 generates dislocations but restricts their propagation and movement. • 30% ZrB 2 coating shows lower stacking fault energy and stronger hardening ability.