Plasma nitriding without formation of compound layer for 38CrMoAl hydraulic plunger

In this study, low temperature plasma nitriding (LPN) was primarily used in 38CrMoAl hydraulic plunger to overcome the peeling problem of the compound layer in real application. The cross-sectional microstructures of the treated samples were observed by optical metallography, phase constituents were determined by X-ray diffraction (XRD), the microhardness profile and brittleness of surface were measured by microhardness tester. The results showed that no compound layer was formed while plasma nitriding at 450 °Cfor 6 h, and XRD also confirmed that there existed no γ′-Fe4N. Meanwhile, the brittleness was decreased at lower temperature plasma nitriding comparing with normal plasma nitriding (NPN), due to no brittle compound layer formed on the outmost layer.