Internal diameter HVOAF thermal spray of carbon nanotubes reinforced WC-Co composite coatings

Abstract

A novel process, relatively fast and scalable compared to existing ones, has been used to incorporate carbon nanotubes (CNT) 0.5 wt% onto commercial WC-Co thermal spray powder. Nano enabled WC-Co/CNT coatings were obtained by internal diameter HVOAF thermal spray at three different spray powers (48, 41 and 34 kW). A general increase in microhardness and decrease in fracture toughness has been found when adding CNT. Also, carbide retention index upon spray was improved by lowering the process temperature and adding CNT, reaching 99% in the low power case with CNT. The interplay of these features has shown an overall better wear performance in the medium power case without CNT; in fact, the addition of CNT has improved the wear performance at high power conditions (reduction of coefficient of friction by half) while reducing the wear performance in medium and low power. A tailored choice of CNT concentration can offer enhanced mechanical or tribological properties according to the needs for different applications. This novel process for nanoparticles incorporation opens the way for the production of large batches of readily usable nano-enabled powder.

Keywords

• HVOAF thermal spray
• Internal diameter spray
• Wear-resistant coatings
• WC-Co
• Carbon nanotubes