Ca-Mn co-doping LaCrO3 coating with high emissivity and good mechanical property for enhancing high-temperature radiant heat dissipation

Two techniques, including spray drying and electrostatic spray, were applied to produce feedstocks for preparing Ca-Mn co-doping LaCrO3 ceramic coatings with two different structures on Ni-based alloy by the atmospheric plasma spraying method. The results show that coating from feedstocks produced by spray drying exhibits lower roughness and porosity than the coating from feedstocks produced by electrostatic spray due to the full melting of smaller feedstocks. Higher proportion of melting zones is beneficial to enhance the ratio of hardness to modulus to improve wear resistance. The emissivity of the coatings with roughness from 0.65 µm to 4.6 µm is all above 0.9 in the waveband of 1–14 µm at room temperature. What’s more, structure-dependent emissivity is affected by surface roughness and pore size due to the infrared scattering. The temperature-dependent thermal infrared emissivity at 1–14 µm decreases with the increasing temperature, and is still above 0.67 at 1200 °C.