Laser Texturing as Substrate Preparation Technique for Improved Corrosion Performance on WC-Co HVOF Coatings on AZ91D

Abstract

Substrate preparation plays a vital role in the performance of thermal spray coatings. Adherence of the coating to the substrate depends on surface characteristics like; mechanical interlocking, physio-chemical properties of surface and metallurgical bonding. The surface characteristics depend to great extent on the method used for substrate preparation. In the present study, WC-12Co and WC-17Co coatings were deposited on AZ91D samples prepared using laser texturing as substrate preparation technique. Laser textured substrate was characterized using scanning electron microscopy and surface roughness tester. Bond strength of the coating was determined using ASTM 633C pull off test. SEM was used to study the morphology of the coating; XRD/EDAX techniques were used to study the structure of the coatings. Porosity and micro-hardness of the coatings were also measured. Corrosion performance of the coatings was determined using Potentiodynamic and EIS electrochemical corrosion testing techniques. The coatings are found to have good surface and mechanical properties. Both WC-12Co and WC-17Co demonstrated good corrosion performance during electrochemical testing. However, WC-12Co was found to better protect the AZ91D compared to WC-17Co.