INFLUENCE OF THE METAL UNDERLAYER ON THE CAVITATION RESISTANCE OF NITRIDED STEEL WITH Mo2N COATING

A complex modification of 25CrMoV steel has been carried out, which includes nitriding in arc-enhanced glow discharge plasma, deposition of metallic sublayer (Mo, Cr or Ti) and deposition of top layer of Mo2N coating. The structure studies showed that depending on the material and the thickness of the sublayer (1.5...6 µm), defects and delaminations could form at the interfaces, while no defects were observed in the absence of the metallic sublayer. The concentration of nitrogen in the complex modified layers depends on the composition of the metallic sublayer, but does not affect the total depth of nitriding of the hardened steel ~ 160 µm. The hardness of the nitrided layer is ~ 12 GPa, and the hardness of the Mo2N coating is ~ 30 GPa. The cavitation resistance of complex-modified 25CrMoV steel without the metal sublayer is 2 times higher than the initial steel.