Khagendra Tripathi

Synergy Effect of Ultrasonic Nanocrystalline Surface Modification and Laser Surface Texturing on Friction and Wear Behavior of Graphite Cast Iron

ABSTRACT Laser surface texturing (LST) followed by an ultrasonic nanocrystalline surface modification (UNSM) process was applied to graphite cast iron to improve the friction and wear behavior. The surface hardness of the UNSM-treated and UNSM + LST-treated specimens was increased significantly compared to the polished and LST-treated specimens. The friction and wear behavior of the specimens was assessed using a ball-on-disk friction tester at an applied load of 10 N and a speed of 5 cm/s in both dry and lubrication conditions. The friction coefficient of the UNSM-, LST-, and UNSM + LST-treated specimens reduced in both dry and lubrication conditions compared to the polished specimen by 64, 30, and 64% and 63, 67, and 75%, respectively. In lubrication condition, the friction coefficient of the UNSM- and LST-treated specimens was further reduced by about 30 and 25% by UNSM + LST processes. In dry condition, the UNSM + LST-treated specimen exhibited a reduction in the friction coefficient of 46% compared to the LST-treated specimen, whereas no reduction in friction coefficient was found compared to the UNSM-treated specimen. The wear resistance of the UNSM-, LST-, and the UNSM + LST-treated specimens was enhanced by 22, 11, and 37% in the dry condition, respectively, whereas minuscule wear was observed in the lubrication condition that was difficult to quantify in our experiment. UNSM and LST processes were effectively combined to improve the friction and wear behavior of graphite cast iron.

Graphene Coating via Chemical Vapor Deposition for Improving Friction and Wear of Gray Cast Iron at Interfaces

This study reports the influence of CVD-graphene on the tribological performance of gray cast iron (GCI) from the internal combustion engine (ICE) cylinder liners by performing a ball-on-disk friction tests. The graphene-coated specimen exhibited a significant reduction (∼53%) of friction as compared to that of the uncoated specimen, whereas wear resistance increased by 2- and 5-fold regarding the wear of specimen and ball, respectively. Extremely low shear strength and highly lubricating nature of graphene contribute to the formation of a lubricative film between the sliding surfaces and decreases the interaction between surfaces in the dry environment. Under the applied load, a uniform film of iron oxides such as Fe2O3, Fe3O4, and FeOOH is found to be formed between the surfaces. It is proposed that the graphene encapsulation with the metal debris and oxides formed between the specimens increases the lubricity and decreases the shear force. The transformation of graphene/graphite into nanocrystalline graphites across the contact interfaces following the amorphization trajectory further increases the lubricity of the film that ultimately reduces friction and wear of the material.

Improved Tribological Behavior of Grey Cast Iron Under Low and High Viscous Lubricants by Laser Surface Texturing

The main objective of this paper was to investigate the effect of laser surface texturing (LST) on the friction and wear behavior of gray cast iron in lubricated conditions. The dimples with a diameter of 54 μm and depth of about 10 μm were produced with various dimple densities in the range from 5 to 35 %. Ball-on-disc friction tests were carried out for all the specimens in low and high viscous oils. The friction coefficient was reduced by about 35 % after the LST compared with the untextured specimen at a load of 5 N and speed of 5 cm/s. The textured specimen with a dimple density of 10 % possessed the lowest friction coefficient of all the dimpled specimens in both low and high viscous oils. However, the high viscous oil was found to be more effective to achieve a lower friction coefficient compared to the low viscous oil. The friction coefficient reduced by about 46 % in high viscous oil compared to the low viscous oil. Similarly, the lower wear was noticed for the specimen with a dimple density of 10 % and 5 % among all the specimens in both low and high viscous oils. The resistance to wear of the specimens was also found to be enhanced in high viscous oil compared to those in low viscous oil.