Improvement in Impact Resistance of Thermally Sprayed WC-Ni Coating/Steel System
摘要
The surface coated components are often subjected to a heavy-load impact condition in practical applications. The impact resistance of thermally sprayed coatings is mainly studied in a low load range, generally less than 1 kN, it is necessary to clarify the damage behaviors of coatings under higher impact loads, providing experimental and theoretical basis for the design of impact-resistant coated components. Measurements under impact load of 1-10 kN order were carried out on the thermally sprayed WC-Ni coatings with different thicknesses and WC-Ni bulk counterparts as bulk materials that used for comparison analysis in damage behavior. Compared with the reported relatively low impact load, a variety of damage behaviors of the coatings were observed including surface extension crack, internal crack, interface extension crack, and interface propagation crack under heavy-load impact. The maximum impact load threshold corresponding to the surface cracking of coatings is three times that of the bulk material, approximately 11 kN, due to the synergistic deformation between coating and substrate. The damage modes of coatings are related to the substrate deformation proportion (Dsp), i.e., with the increase in Dsp, the plastic deformation of coatings and the spallation and collapse of WC grains occur first, and then the cohesive failure and/or adhesive failure. Moreover, the combination of Dsp and the critical value CV-Dsp can be used to speculate the limit load preventing cracking failure for different coating thicknesses.