THE EFFECT OF THE PARTICLE SIZE FRACTION OF CR3C2-NICR POWDER ON THE STRUCTURE AND PROPERTIES OF COATINGS DEPOSITED BY THE HVOF METHOD

Аңдатпа

This study investigates the effect of the particle size fraction of Cr₃C₂-NiCr powder and of the spraying distance on the structure, porosity, and hardness of coatings deposited onto a 12Kh1MF steel substrate by high-velocity oxygen fuel (HVOF) spraying. Five samples were prepared: B1 (powder particle size 0–20 μm, spraying distance 300 mm), B2 (20–32 μm, 300 mm), B3 (32–40 μm, 300 mm), B4 (32–40 μm, 250 mm), and B5 (32–40 μm, 200 mm). The microstructure of the coatings was examined by scanning electron microscopy (SEM); porosity was determined from SEM images using ImageJ software; the elemental distribution was assessed by EDS mapping; and hardness was measured with a FISCHERSCOPE HM2000 instrumented indentation system in accordance with DIN EN ISO 14577-1. Increasing the powder particle size at a spraying distance of 300 mm was found to increase the coating thickness, but it may also increase porosity. The greatest coating thickness, 253.14 ± 8.63 μm, was obtained for sample B5, although its porosity reached 6.569%. The lowest porosity (2.909%) and the highest hardness were recorded for sample B4: HM = 8063.2 ± 619.5 N/mm², HV = 1251.5 ± 107.1. The results show that, among the conditions studied, the optimal regime is the spraying of 32–40 μm powder at a distance of 250 mm, which ensures the formation of a denser and more uniform Cr3C2-NiCr coating.