Exploration of electrodeposited process of Ni-Co-Cr coating and investigation of Cr doping strengthening mechanism by indentation simulation

Ni-Co-Cr coating with excellent mechanical properties was successfully prepared by the electrodeposition process. Compared with the binary Ni-Co alloy coating, the hardness of the ternary coating is increased to 1247HV, an increase of 61%. The wear rate decreased by 40.7%. The exploration of the deposition process found that sodium formate and urea can effectively dissociate [Cr(H2O)6]+3 complexes to realize the co-deposition of Cr3+. The strengthening mechanism of Cr doping was then investigated by molecular dynamics indentation simulation. It is found that grain refinement and solid solution strengthening contribute 20% (0.33 GPa) and 80% (1.33 GPa) to the hardness, respectively. The enhanced covalent character between Cr and solvent atoms improves the elastic modulus and promotes the dislocation nucleation, which originates from body-centered cubic-like (BCC-like) defect clusters. In the plastic deformation stage, Cr doping reduces the stacking fault energy of the alloy and makes the release of the plastic strain more uniform and stable. The denser 3D stacking fault network structures hinder the further propagation of dislocation loops and increase the dislocation reaction probability. More Lomer-Cottrell and Hirth Locks are generated and improve the strength of the coating.