Statistical Design of HVOF Spray Experiments to Manufacture Superfine Structured Wear Resistant Cr3C2 - 25(Ni 20Cr) Coatings

Thermal spraying of novel submicron or nano-scaled feedstock materials can provide the deposition of cermet coatings with significantly improved characteristics and is recently of great interest in science and industry. However, due to the large specific surface and the low specific weight, fine particles do not only show a higher thermal susceptibility and a different thermo-kinetic behavior in the HVOF process than conventional coarse-grained powders, but also feature a high tendency for particle agglomeration. In order to process fine powders and to preserve the submicron structure of the feedstock in the final, as-sprayed coating morphology, the use of novel thermal spray equipment as well as a thorough selection and optimization of the process parameters are required. In this study, HVOF spray experiments have been conducted to manufacture superfine structured, wear resistant cermet coatings with improved macroscopic properties using Cr₃C₂ 25(Ni 20Cr) submicron powders (2 - 8 µm). Statistical design of experiments has been utilized to identify the most relevant process parameters along with their interaction effects using Plackett-Burman and fractional factorial designs. Response surface methods and Derringer’s desirability function have been employed to simultaneously optimize majorly important coating characteristics such as roughness, hardness and porosity.