Tribological study on cast iron based, graphite and CNT enriched hybrid HVOF coating from room temperature to 300°C

Abstract

ABSTRACT In this article, eco-friendly graphite has been produced from the carbonised rice husk, an environmental waste. Graphite, carbon nanotube (CNT) and cast iron powder were blended to produce the hybrid coating material. This hybrid coating material was deposited over the cast iron substrate using HVOF thermal spray. The microhardness of the coated sample increased by 42% as compared to the substrate. The morphological and elemental analysis was carried out using SEM, XRD and raman spectroscopy. The residual stresses developed in the coated sample were measured using an X-ray analyzer and found to be compressive, indicating a stable coating. A tribological investigation was carried out on a Pin-on-disc tribometer at ambient, 150°C, and 300°C temperatures. The coefficient of friction and specific wear rate reduced by ≈ 62% and ≈ 47% respectively. The SEM investigation showed evidence of free graphite as a solid lubricant over the coated samples.