Hypereutectoid steel coatings obtained by thermal flame spraying - Effect of annealing on microstructure, tribological properties and adhesion energy

Metallic coatings were processed on a 35CrMo4 substrate using a thermal flame spray technique. The deposited metal was a high carbon steel, low alloyed with Cr, Mn and Si. In those coatings FeO and Fe3O4 oxides were found, as well as stable α-ferrite phase and some γ-austenite phase. γ-Austenite phase is metastable and transforms into stable α-ferrite during annealing treatment at 300 °C. This γ to α-phase transformation, as well as the evolution of the oxides during the annealing post-treatment, has some influence on the mechanical properties of the coating: hardness, tribological properties, Young's modulus and adhesion on the 35CrMo4 substrate.