Effects of spraying parameters onto flame-sprayed glaze coating structures

Thanks to their design characteristics (i.e., colors, brightness, opacity, etc.) and/or physical properties (i.e., durability, low thermal conductivity, tightness, etc.), glazes find numerous applications, from art ornamenting to protection against corrosion. Glazing consists in coating a substrate by fusing various mineral substances over it. This is a low cost process and hence can be applied on large surfaces. Conventional glazing process needs a relatively high temperature treatment (i.e., up to 1400 °C) that heat-sensitive substrates do not sustain.Thermal spraying may be a good solution to prevent the substrate from thermal degradation. Flame spraying was considered as the spray technique due to its low operating cost and the possibility to adapt the glaze transition temperature to the operating parameters.When spraying glazes, the coating formation mechanism is different from the one encountered with crystallized ceramic materials. Indeed, the high surface tension of those feedstock prevents the particles from being totally spread (i.e., “dewetting” phenomena). Here, the coating results from the coalescence of impinging particles to form a monolayer.The effects of glaze morphology on coatings were studied in this paper. Chemical analysis also permitted to determine the influence of spray parameters on glaze compositions, that can affect glazes thermal properties and hence modify coating structures. At last, the effects of operating parameters on coating architecture were analyzed by experimental design.