Corrosion behaviour of WC-Co coating on Ti6Al4V using Detonation Spray

Abstract

In this work, thermal barrier surface coatings were applied on Ti6Al4V substrate using high velocity oxy fuel (HVOF) to improve corrosion resistance. The ceramic coating (WC–Co) were deposited on Ti6Al4V substrate with different thicknesses such as 250µm, 350µm and 450µm. In the present investigation, hardness of both coated specimens and substrate were found by conducting Vickers hardness test. The cross sectional and surface morphology of substrate and coated system with varying thickness were made using SEM. In the present investigation, hardness of both coated specimens and substrate were found by conducting Vickers hardness test. The porosity of coated system was carried out by using SEM. The bonding strength of the coatings was examined by pull-off test using Instron tester (Model 1121) with a stretching rate of 2mm/min. XRD characterisation was performed for substrates and coated samples. The cross sectional and surface morphology of substrate and coated system with varying thickness were made using SEM.

Potentiodynamic polarization tests were conducted in Ringer’s solution (at 37°C and pH value was set to 5.7) to investigate the corrosion performance of coated samples and substrate. Finally the results reveal that 250 and 350µm thickness coated samples showed substantial improvement in corrosion resistance compared to bare substrate. However, the 450µm thickness coated samples showed poor corrosion resistance compared to substrate. The scale formed on the samples upon corrosion was characterized by using SEM analysis to understand the degradation mechanisms