The influence of reinforcement of carbon nanotubes (CNTs) on microstructural features and mechanical properties of thermally sprayed Al2O3–3[Formula: see text]wt.%TiO2 and WC–20[Formula: see text]wt.%Co coatings was investigated. Alumina–Titania coatings were deposited by Air Plasma Spraying (APS) and Tungsten Carbide–Cobalt coatings were deposited by High-Velocity Oxy-Fuel (HVOF) spraying process. The coatings obtained with reinforcement of CNTs were characterized to interpret the microstructural changes and also to evaluate the variation in their mechanical properties. The percentage composition of CNTs in both APS and HVOF coatings systems were varied in the order of 2, 4, and 6[Formula: see text]wt.%. It has been found that homogenous dispersion of carbon nanotubes in the coating systems results in increased microhardness and reduced surface roughness. Also, the microstructural features of the coating systems clearly showed that the coatings are denser with fewer pores due to the presence of CNTs.
Tungsten Carbide-20 weight % Cobalt (WC-20 wt% Co) coatings were extensively used material to achieve a combination of extreme hardness and excellent strength. Hence, an effort has been made to improve the toughening properties of WC-Co coatings through reinforcement of Carbon Nano-Tubes (CNTs) using High-Velocity Oxy-Fuel (HVOF) spraying process. In this work, 2 wt%, 4 wt%, and 6 wt% of CNTs were blended by the ball milling process with WC-Co powders. These composed powders were deposited by HVOF process on to the plain mild steel substrates. The scratch test analysis on as-sprayed coatings showed that due to the addition of CNTs on WC-Co coatings, the resistance to penetrate the coating surface increased. Also, by varying the percentage of CNTs in the coating system, the pores were reduced. This phenomenon is attributed to the toughening mechanism by forming a CNT bridge which avoids the formation of internal cracks.
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