High temperature spectral selective TiC-Ni/Mo cermet-based coatings for solar thermal systems by laser cladding

Thermal instability and quite high infrared emissivity at high temperature is one of the great challenges in the development of concentration solar power (CSP). Herein, a new single layer multi-scaled nanostructured TiC-Ni/Mo cermet-based spectral selective coating fabricated by the laser cladding method on stainless steel at atmospheric pressure are explored in this study. This method helps to attain the desired coating roughness which the solar absorptance of ∼86.2% has been experimentally measured and thermal emissivity of ∼4.2% at 300 K was calculated. After anneal at 600 °C for 200 h in air, the coating still showed a low thermal emissivity of ∼4.7% and a high absorptance of ∼84.7%. A high selective receiver efficiency of ∼82.0% has been achieved for laser cladding coatings. This low thermal emissivity and high solar absorptance was got by a single laser cladding layer having sub-micron surface roughness using fractal nanostructure with characteristic metal particle sizes in the range from nanoscale to microscale. These results show that the laser cladding TiC-Ni/Mo cermet-based absorbing coating would be suitable for high temperature application because it can satisfy the operating temperature of ≥600 °C in air.