Improvement in Microscratch Resistance of Graphite by Surface Modification for Molding Applications

Abstract

This paper deals with the improvement in surface properties and microscratch resistance of graphites by means of an ultrasonic nanocrystalline surface modification (UNSM) technique. The surface roughness and surface hardness of the untreated and UNSM-treated graphites were investigated using an atomic force microscopy (AFM) and a microhardness tester, respectively. The scratch resistance was assessed using a microscratch tester at a progressive load. Moreover, a Raman spectroscopy was employed to characterize the microstructure of graphites before and after UNSM treatment. The scratch test results revealed that the resistance to scratch of both UNSM-treated graphites was found to be better in comparison with the untreated graphites. The increase in scratch resistance of both UNSM-treated graphites may be mainly attributed to the reduced surface roughness and increased surface hardness by UNSM treatment. The graphite produced by Poco exhibited a higher resistance to scratch compared to that of the graphite produced by Mersen. The objective of this study is to extend the service life of three-dimensional (3D) cover glass moldings made of graphite by the application of UNSM treatment through the understanding the effects of surface roughness and surface hardness on the scratch defect generation behavior during glass molding process.

A review of recent advances in tribology

“…It is considered that the UNSM treatment can generate large compressive residual stress, refine grain sizes in the subsurface, and increase surface hardness, resulting in a higher wear and micropitting resistance [282−285]. The technique has been applied to bearing raceway [282], ball screws made of SCM445H, NF42CD4, and SAE4150 [283], and even graphite used in cover glass moldings [284]. The UNSM treatment was also combined with surface texturing to improve the wear resistance of spherical plain bearings used in aircrafts [285].…”