Influence of Elements in Steel With Anode Plasma Electrolytic Boriding on Hardness Gradient and Tribological Properties

The influence of elements in steel on anode plasma electrolytic boriding has been studied. The modified layers and surfaces on steel samples were analyzed by a scanning electron microscope, an X-ray diffractometer, a surface profiler, a microhardness tester, and a ball-disc tribometer. With 1045 steel as the control group, the same treatment parameters (treatment with 5 min, 200 V of voltage, 5% boric acid, and 10% ammonium chloride) were implemented on various steel substrates. It was found that a low content of carbon would hinder the penetration of boron, and other metallic elements can improve the mircrohardness gradient and decrease the wear-rate. Chromium and manganese can increase the maximum microhardness than treated 1045 by about 15%, but have a detrimental effect on surface flatness. Nevertheless, manganese has the ability to rapidly create a layer of oxide that enhances the tribological characteristics, leading to a remarkably low average friction coefficient of 0.26 for 1046 steel. The presence of molybdenum in the element composition of 4140 steel results in a notable enhancement of surface properties, namely in terms of wear resistance, with a minimum wear-rate 2.1 × 10−6 g/Nm for 4140 steel. Nickel does not appear to have a notable impact on the surface characteristics of the modified samples.