Effects of hBN Content on Thermal Shock Resistance and Oxidation Properties of NiCr/Cr_3C_2-hBN Composite Coatings

In order to improve the tribological properties of the NiCr/Cr3C2 composite coatings,the hBN was added into the coatings as lubrication.The effects of hBN content on the thermal shock resistance and oxidation properties of the coatings were investigated.The NiCr/Cr3C2-hBN composite coatings with 0%,2.5%,5%,10% and 20% of hBN content were prepared by atmospheric plasma spray(APS)technology.The thermal shock resistance at 700,800,and 850℃and the oxidation kinetic curve at 850℃ of the APS sprayed NiCr/Cr3C2-hBN composite coatings were investigated by muffle furnace.The results show that:the NiCr/Cr3C2-hBN composite coatings consist of elongated lamellae and exhibit excellent tensile strength.The cracks and spallings are not observed after water quenching ten times at 700,800 and 850 ℃.All the composite coatings exhibit excellent thermal shock resistance property at 700,800 and 850℃.The weight gain of the coatings increase with the increase of hBN content.The NiCr/Cr3C2-20%hBN coatings are seriously oxidized after96 h.At 850 ℃,the oxidation kinetics curves of the coatings all basically follow the parabola law.