In one embodiment, a substrate, for example a tool used in hot metalforming operations, is coated with an enamel nanoparticulate graded coating. The nanoparticles in the coating may be boron nitride nanoparticles. The coating may include a first portion adjacent a surface of the substrate, and a second portion adjacent the first portion. The first portion of the coating may have a lower volume fraction of nanoparticles than the second portion. The first portion has excellent adhesion to the surface of the substrate, and the second portion reduces friction and wear. The coated tool may be formed by applying at least one layer of a coating mixture to a surface of the tool and heating the coating mixture. A metal workpiece may be formed into an article by contacting the metal workpiece against the coated surface of the tool.