Enhanced Surface Properties of 1080 Eutectoid Steel by Cathodic Cage Plasma TiN Deposition

AISI-1080 eutectoid steel is a low-cost material, which is widely used in several industries, including machinery parts and tools. However, surface modifications are necessary to upgrade the mechanical and tribological properties. Common heat treatments for surface modification of eutectoid steel are reported in the literature. In this work, the cathodic cage plasma deposition (CCPD) technique consisting of a titanium cathodic cage is used to deposit a titanium nitride (TiN) coating on eutectoid steel, and noteworthy improvement in surface properties is obtained. The effect of sample biasing and gas composition (nitrogen–hydrogen) on surface properties is examined. The cathodic samples exhibit iron nitrides (Fe₂N, Fe₄N) with minor TiN phases, and, at floating potential, the sample contains iron nitrides (Fe₃N, Fe₄N) and TiN phases. The hardness is upgraded to 1100 HV_0.25 when the samples are treated at floating potential with higher hydrogen contents, much higher than the hardness reported by other treatments. The wear volume obtained by the micro-abrasive wear test is reduced after the coating deposition, and the lowest wear volume is obtained at floating potential with higher hydrogen contents (10^-2 mm³), whereas the untreated sample exhibits wear volume (42 × 10⁻² mm³). This study suggests that, instead of conventional heat treatments with a high temperature and extended treatment time, CCPD TiN deposition at floating potential with optimum gas composition is much more advantageous for eutectoid steel's hardness and wear resistance.