Study of the influence of a gradient gas flow as an alternative to improve the adhesion of Diamond-Like Carbon film in the wear and corrosion resistance on the nitrided AISI 4340 steel

Diamond-Like Carbon (DLC) films have been widely studied due to their interesting properties, but this film presents low adhesion on metal surfaces. Interlayers have been performed, between the substrate and the DLC film, combined with previous surface treatment as plasma nitriding to improve film adhesion on the surface. This work aims to develop a multilayer treatment of nitriding, gradient treatment, and DLC film deposition without organosilicon interlayer to determine the synergic influence of treatments on multilayer adhesion, wear, and corrosion resistance of the AISI 4340 steel. Plasma surface treatments such as simple nitriding, simple DLC film deposition, which consists of treatments performed individually, multilayer treatment of nitriding + DLC with and without an organosilicon interlayer, and multilayer treatment of nitriding + gradient treatment + DLC without interlayer using gas flow gradient were carried out using a pulsed-DC power supply. The highest wear and corrosion resistance was obtained by the multilayer treatment with organosilicon interlayer due to the synergic effect of this interlayer with the DLC film and nitriding treatment, but the multilayer treatment without organosilicon interlayer performed with gas flow gradient presents better corrosion and wear properties compared with simple treatment. Results have shown that it is possible to perform multilayer treatments with the presence and the absence of an organosilicon interlayer, keeping wear, corrosion, and adhesion properties of the DLC film on nitrided AISI 4340 steel deposition.