Flame spraying of adherent silicon coatings on SiC substrates

Thermally sprayed silicon coatings seem a good bond coat option for state of art environmental barrier coatings (EBCs) aimed at protecting the high temperature ceramic components of the next generation of gas turbine engines. In this paper, Si has been flame sprayed, by tailoring the spraying parameters and substrate roughness for achieving well adhered, dense Si coatings over SiC substrates. Thermal conductivity and hardness measured on these Si coatings show analogous or even higher values than those reported for similar plasma sprayed Si coatings. Scratch test is proven to be a valuable method to estimate the adhesion of the coatings to the substrate. For the first time the thermal conductivity of thermally sprayed Si coatings is calculated, showing a relatively high value of 35.4 W·m− 1·K− 1 at room temperature. The estimated thermal contact resistance at the Si/SiC interface varied from 1.5 · 10− 5 to 5.8 · 10− 6 m2·K·W− 1 in the 25-400 °C temperature range.