Mine you, maybe, coatings WC-Co, WC-Co-Cr, which are applied by high-speed flame spraying (HVOF / HVAF)? These coatings contain fine tungsten carbide, the size of which is about 0.5-1 μm. Whether this fits under the term "Nano" is questionable. The term "submicron" is more appropriate.

By the way, we produce such layers as standard.

Thanks for your response , the nano powder used had size of 50nm

The best technique for coat grey cast iron by nano carbide tungsten is sputtering deposition‬‏.

Thank you