Crack defects and formation mechanism of FeCoCrNi high entropy alloy coating on TC4 titanium alloy prepared by laser cladding

• The influence of the coating stress field distribution on the crack of cladding layer was investigated. • The cracks in coating were classified and their initiation and propagation mechanism was interpreted. • The influence of single factor and double factor interaction on crack rate was evaluated. • The crack rate of coating was proposed through linear regression analysis. Laser cladding technology, a promising surface modification method adopted to fabricate a high entropy alloy (HEA) coating on the surface of TC4 titanium alloy, can competently solve the problems of wear, corrosion and fracture of titanium alloy in practical applications. The current study utilized a finite element model to investigate the influence of powder layer thickness and process parameters on the stress field. The effect mechanism of stress on cracks was preliminarily explored based on the simulation results of the stress field. The cracks in the FeCoCrNi HEA coating were classified, and their initiation and propagation mechanism was interpreted. The influence of single-factor and double-factor interactions on the crack rate was evaluated combined with the experimental and simulation results. Linear regression analysis was performed to propose empirical-statistical correlations between the key processing parameters and the crack rate of the FeCoCrNi HEA coating. The results indicated that the interaction between laser power and scanning speed significantly impacts the crack rate of the FeCoCrNi HEA coating. The maximum stress value in the fusion zone at the bottom of the coating demonstrates that crack initiation and propagation are prone to materialize in this zone. This study provides a referenced value on the excellent crack control and the comprehensive properties improvement of the coating in high entropy alloy laser cladding.