XPS analysis on tribofilm formation study for metal sliding surface

• Main Author: Md Yasser, Mona Alis
• Format: Thesis
• Language: English; English; English
• Published: 2022
• Subjects: T Technology (General)
• Online Access: http://eprints.uthm.edu.my/8282/1/24p%20MONA%20ALIS%20MD%20YASSER.pdf; http://eprints.uthm.edu.my/8282/2/MONA%20ALIS%20MD%20YASSER%20COPYRIGHT%20DECLARATION.pdf; http://eprints.uthm.edu.my/8282/3/MONA%20ALIS%20MD%20YASSER%20WATERMARK.pdf; http://eprints.uthm.edu.my/8282/
• Institution: Universiti Tun Hussein Onn Malaysia

Mineral oils and Synthetic Ester (SE) are widely used as lubricants in manufacturing industry. However, the resources depletion and environmental pollution effects of these two lubricants occur and this research presents the significance of Modified Jatropha Oils (MJO) (vegetable oil) used as bio-based lubricants for machining lubrication. MJO was enhanced with Ammonium Ionic Liquid (AIL) and Phosponium Ionic Liquid (PIL) additives under selected nominal percentage weight; 1%, 10% for AIL and 1% for PIL. The difference in nominal percentage weight determined from the machining performance. This led to various results on thin film; also known as tribofilm where it is formed at the tool-chip contact region due to the friction occurred during sliding contact of two bodies in the presence of lubricants. Throughout the literature review, previous researches are aware regarding bio-based lubricants application to reduce pollution and formation of tribofilm built up by oxide layers at the tool-chip contact region. The mixtures of MJO, MJO+AIL1%, MJO+AIL10%, MJO+PIL1%, and SE samples undergone a physicochemical test under American Standard for Testing Materials (ASTM) D6751). Fourier Transform Infrared (FTIR) used to determine functional groups in the bio-based lubricant mixtures. X-ray Photoelectron Spectroscopy (XPS) was employed to study the characteristics of tribofilm formed and its composition in weight percentage. Physicochemical test and FTIR bandwidth vibration showed all lubricants satisfied the ASTM D6751 standard the fingerprints of alkane, alkene, and hydroxide from all samples tested. From the XPS findings, W4f curve represents the contribution of Tungsten. Narrow scan of W4f photoelectron peak showed no presence of WS2 compound for the non-lubricated tool-chip contact region. However, the percentage concentration of the WS2 compound has increased from the value of 9.27% for MJO+AIL 1% and 32.43% for MJO+AIL 10%. In conclusion, WO2 is agreed as a sacrificial layer that its decrement correspond to the increment of WS2 where the thermodynamic is the factor to the breaking of the chemical bonding, led to the chemisorption between W4+ ion from the cutting tool and the S2- from the lubricants.