Highly reflective ZrC-Cu-based metal matrix composite coatings deposited via cold-spray for laser protection applications

Lasers are very powerful and can produce high temperatures, capable of melting materials when projected with an appropriate power, exposure time, distance, and beam width. High energy lasers are used for attacking enemy aircraft and missiles; however, the same threat is inevitable to the allied aircraft and missiles. Surface coatings have proven to be a viable solution to reduce damage from such laser attacks. In the present work, ZrC-Cu-based highly reflective coatings were deposited on Al-6061 alloy using the cold spray to develop laser damage resistance. Microstructural characterization, XRD, micro-hardness, reflectivity measurements, and laser ablation tests were conducted on the developed materials. The results showed improved ceramic retention and mechanical properties along with minimal porosity in the coating with increasing ZrC content in the feedstock. Additionally, the XRD analysis revealed that Cu-ZrC composite coatings could be produced by cold spray, without decarburisation of ZrC or oxidation of Cu. Owing to the exceptional purity in coatings, highly reflective coatings were obtained. At the target wavelength of 1080 nm, Cu-30 %ZrC composition achieved a remarkable reflectivity of 75 % (85 % of bulk copper). The coatings with compositions of Cu-30 %ZrC, Cu-50 %ZrC and Cu-70 %ZrC remained undamaged under laser irradiation, whereas Cu-85 %ZrC exhibited a laser ablation pit. These findings provide valuable insights into developing optimized ZrC-Cu coatings against laser irradiation.