The enhancement of the properties of WC-Co HVOF coatings through the use of nanostructured and microstructured feedstock powders

Abstract

Three coatings have been obtained using nanostructured, bimodal and conventional WC-Co cermet powders by means of High Velocity Oxygen-Fuel (HVOF) technique. Propylene has been used as fuel gas. All the powders have been sprayed under the same spraying parameters. These powders and the coatings obtained have been characterized using XRD and SEM. The friction wear resistance of the coatings has been studied by Ball-on-Disk test (ASTM G99-90), and the abrasive wear resistance has been quantified by Rubber-Wheel test (ASTM G65-91). Finally, the corrosion resistance has been studied by electrochemical techniques and salt fog spray test. The nanostructured coating shows more hardness than the other ones, but the bimodal coating have showed better abrasive and friction wear resistance. Both nanostructured and bimodal coatings have showed good corrosion resistance, better than the conventional coating of WC-Co. The bimodal powder has the advantage of being less expensive than the nanostructured powder, and even providing better properties.