Effect of Surface Texture-Active Screen Plasma Nitriding Duplex Treatment on Tribological Behavior of 38CrMoAl Steel

Abstract

Purposes 38CrMoAl steel is often used as pistons in a hydraulic pump, its surface performance is especially important for long-life safe working. Wear is the main failure mode of pistons in a hydraulic pump. With surface strengthening treatment, it is able to break through its performance limit and realize high performance and reliable operation of a hydraulic pump. Methods In this work, the pattern and performance on the surface of 38CrMoAl steel has been regulated by a duplex treatment of surface texturing (ST) and active screen plasma nitriding (ASPN), aiming to achieve strengthening on its surface. Dimple texture with different shapes were first prepared on 38CrMoAl steel surface by laser processing technology. 38CrMoAl steel samples with and without textured surface have been treated by ASPN. A ball-on-disc friction and wear testing machine was employed to investigate the effect of surface texture-active screen plasma nitriding duplex treatment on the tribological behavior of 38CrMoAl steel. Findings The results show that ASPN layer is mainly built up by the phases of ε-Fe2-3N, γ′-Fe4N and CrN. The ASPN layer is compact, and free of obvious cracks and holes. Meanwhile, it is found that the uniform and continuous ASPN layer consists of a white bright layer and a diffusion layer. The hardness across surface to the inside of the ASPN layer has demonstrated a gradient distribution, where the highest hardness value is detected on the surface, and the hardness decreases as the distance from the surface increases. According to the dry sliding friction results of 38CrMoAl steel related samples against Al2O3 balls, the coefficients of friction of 38CrMoAl steel and ST＋ASPN-38CrMoAl steel are 0.40 and 0.36, respectively. The ST＋ASPN-38CrMoAl steel presents a 92.5% reduction in mass loss, as compared with 38CrMoAl steel. It can be concluded that surface texturing-active screen plasma nitriding duplex treatment endows the working surface of 38CrMoAl steel with enhanced tribological performance.

Keywords

• surface texture
• active screen plasma nitriding
• duplex treatment
• 38crmoal steel
• tribological performance