Tribological performances of Ni3Si-Cr7C3 composite coatings under water and acid environments

► Ni3Si-Cr7C3 coatings show excellent wear resistant in sulfuric acid solution. ► Coating exhibits optimal tribological performance, which contains 37.2% Cr7C3. ► COFs was lower in sulfuric acid solution than that under water lubrication. ► Wear mechanisms of the composite coatings are microploughing in both conditions.