Tribological behavior of borocarburized layer on low-carbon steel treated by double glow plasma surface alloying

Abstract

In this paper, the borocarburized layer was fabricated on the surface of low-carbon steel via double glow treatment to enhance the wear resistance. Benefited by the gradient structure of an outermost boride layer and inner carburized layer, the bonding strength of the protective coating was improved. The novel design improved the mechanical properties at the coating-substrate interface and extended the service life of the coating. The microstructure and composition of borocarburized layer were analyzed by SEM, XRD, XPS. The tribological properties of substrate and borocarburized layer under dry sliding against ZrO2 ball were investigated. The results indicated that borocarburized layer consisted of a 38 μm boride layer with main phase of Fe2B and a 75 μm carburized layer with main phase of Fe5C3. The microhardness of borocarburized layer emerged in gradient distribution attributed to the double glow plasma surface alloying technique, and the maximum value was around 1700 HV. In addition, the major wear mechanisms of low carbon steel were fatigue and abrasive wear, which transformed to abrasive and adhesive wear with the load increased. The wear mechanisms of borocarburized layer were abrasive and adhesive wear. During wear process, borocarburized layer with high hardness against ZrO2 ball due to the decreased real contact areas. Therefore, the borocarburized layer fabricated on low carbon steel enhanced the wear resistance effectively.