Microstructure and properties of WC-based detonation coatings with residual stresses of different types

Detonation spraying of WC-12Co, WC-10Co4Cr and WC-12Ni coatings was performed on a CCDS2000 facility using explosive mixtures based on a two-component fuel, aС₂Н₂ + bС₃Н₆ + cО₂. The coatings were formed on carbon steel substrates. The detonation gun barrels used for spraying were of three different configurations to produce tensile and compressive stresses as well as an unstressed state in the coatings. Studies of the microstructure, hardness, adhesion, abrasive wear, friction wear, and corrosion resistance of the coatings were carried out in order to identify their dependence on the type of residual stresses. The results show that coatings with compressive residual stresses exhibit significantly higher hardness and wear resistance under sliding friction than coatings with tensile stresses and, although less noticeable, an increase in wear resistance under abrasive wear. Namely, when the WC-12Co, WC-10Co4Cr and WC-12Ni coatings with compressive residual stresses were compared with those with tensile stresses, the former were found to possess higher hardness by a factor of 1.22, 1.15 and 1.32, respectively, and lower friction wear losses by a factor of 1.37, 2.34 and 1.81, respectively. Corrosion tests in the salt spray environment showed that all coatings in the as-sprayed state corrode in the same manner regardless of their composition and the type of residual stresses. Coatings impregnated with a mixture consisting of Metcoseal AP and Metcoseal APT diluent (3:1 v/v) resist corrosion much better than the non-impregnated coatings. Herewith, in the case of WC-12Ni, the coating with compressive residual stresses showed the highest resistance to corrosion.