Wear Behavior of DLC Coated HSS with Hydraulic Fluids

Abstract

The worldwide rotary pump market was estimated at around $5000 million in 2020 and the market is supposed to increase by 20% toward the end of 2026, seeing a compounded annual growth rate of 3% over a period from 2022-2026. The scrapping of an engineered component made from non-renewable resources at an early stage in life due to wear goes against the ethics of the conservation of natural resources as the frictional processes lead to dissipation of a part of input energy. In this context many research works focused on analyzing wear behavior using various formulated and vegetable oils but no works investigated on using hydraulic oils as lubricant for wear preventative nature. The objective of the work was to obtain diamond-like carbon coating on high-speed steel samples and test them for better wear preventative behavior with different hydraulic fluids. The HSS ball sample of 12.7 mm diameter were used as a substrate on which the dlc coating was to be developed using then RF-PECVD technique. The developed DLC coating was characterized by conducting X-Ray diffraction which suggested the coating to be of amorphous structure, Raman spectroscopy which determined the content of graphite (sp2 ) to be 47% and that of diamond (sp3 ) to be 53%.Further nanoindentation was conducted to compare the hardness of the high-speed steel sample before and after coating which was 12.22GPa and 35.56GPa respectively. The four ball test was performed to investigate the anti-wear properties of lubricating oil at specific conditions such as higher load, controlled temperature and constant rotating speed of the ball as per the ASTM D4172. The four ball results show that the coefficient of friction for samples reduces by around 36% when test oil 3 is used in uncoated samples and 48% in coated samples. Also, the wear rate for the test oil 3 for coated samples was found to be 0.7381x10-6 mm/Nm, which is the lowest wear rate among the other test oils. The outcome of the project is the reduction of coefficient of friction by 84% with respect to dry condition when test oil 3 is used. Therefore, it can be deduced that test oil 3 stands out as the most effective lubricant among the trio of test oils.In this direction , further work can be carried out by carrying out four ball tests with lubricant oils in combination with additives to it so as to enhance the base oil property and suppress undesirable base oil properties. Fabrication and manufacturing of the vane model can be done to validate the result with the help of experimental work. Key Word: DLC; HSS; Raman Spectrograph; AFM; 4-Ball Test, Hydraulic Oil.