DLC/a-Si:H multilayers films to improve wear resistance of components of common rail injection system

Abstract

The Common Rail Injection System (CRIS) is diesel engines' main fuel injection system. Due to market needs, such as replacing fuel from diesel to biodiesel, several mechanical problems were observed, including the wear of the metallic components. This paper proposed improving the wear resistance of steel SAE 1045, which can be used in some elements of injection systems, by depositing DLC multilayer films using a plasma Duplex treatment. Firstly, the samples were nitrided in atmospheric plasma and then coated with thin films of DLC/a-Si:H multilayers using a modified pulsed-DC PECVD system. The duplex treatment may reduce friction and consequently facilitate sliding contact. The tribological tests were performed in a cylinder-disc tribometer designed and constructed exclusively to simulate the real contact of components under pressure and movement conditions in the CRIS. The results showed a considerable increase in surface hardness due to the formation of iron nitrides. The DLC/a-Si:H coating reduced the surface roughness because of the plastic deformation of this layer after the tribological tests. Also, this mechanism contributed to the decrease in wear and improved performance of the studied component.