Analysis of electrochemical machining-textured surfaces under point contacts in rolling tribo-test.

Abstract

Purpose: The need for the right textured surface and selecting the right material in tribology is critical to friction reduction and energy savings in machine elements under full film lubrication rolling point contacts. This study provides a guide to proper material selection and the right surface texturing technique to enable machine elements to carry heavy loads at different speeds under the fully-flooded EHL regime.

Design/Methodology/Approach: A lapped GCr15 ball bearing, cast iron (HT 500) plates, GCr15 tempered plates and GCr15 plates without tempering were used. The electrochemical machining (ECM) technique was used to manufacture Micro-texture surfaces on the plates. The ECM micro-textured surfaces and lapped plain surfaces of the same material were subjected to friction and wear behaviour between a ball and a plate test in a fully-flooded EHL point contact rolling condition. The tribological test was conducted under different rolling speeds and pressure. The topographical characteristics of the lapped plain surfaces and the Electrochemical Machining (ECM) textures surfaces were analysed by both optical and scanning electron microscopy.

Findings: The outcome of the study showed that the geometry characteristics (micro-textured and lapped untextured) and the densities of the micro-texture impact was critical to the film formation in the tribological behaviour test against the lapped GCr 15 steel bearing balls. Significantly, low friction and wear were observed for the micro-textured surfaces as compared to the lapped untextured surfaces.

Research Limitation/Implications: The research was on rolling point contact in fully-flooded EHL tribo-test using lapped untextured and micro-textured surfaces in contact with ball bearing. The study did not consider line contact and sliding force. The rolling point contact is the predominant phenomenon in gears, cams, tractions and balls in energy transmission.

Practical Implication: The outcome of this research increase the knowledge base of this area, it informs technologies and tribologies to select and design machine elements with energy-saving criteria in mind. In addition, this work has opened other opportunities for research to harness the full potentials of the micro-texturing.

Social Implication: This paper also guides to industrial and manufacturing sectors using machine elements as moving systems to generate and transmit energy in adopting energy-saving systems and policies that is based on the outcome of such studies.

Originality/Value: The innovation of this research is centered on the tribological performance of GCr15 undergoing Micro-texturing by Electrochemical Machining which demonstrates better film thickness formation within EHL regime over HT 500 counterpart material. This outcome is a good starting point for further research and development.