Exploring the mechanics of adhesion in metal cutting

Exploring the mechanics of adhesion in metal cutting

Production cost and productivity depend on the relationship between the achieved tool life and the cutting data. It is readily accepted that adhesion is one of the man wear mechanisms in metal cutting, besides, adhesive wear can exist during the whole cutting process. In addition to shortening the tool life, it can devastate the machined surface quality. Deposits adhere onto the rake, and the clearance tends to end on the workpiece surfaces. Worn cutting edges affect the surface finish, integrity, fatness, and cutting forces. Changes in cutting forces during the life of the edge give undesired measure deviations.

The demands of surface integrity are often one of the main reasons for using coolant and lubrication of the cutting zone. In the workpiece material, non-metallic inclusions like MnS, SiO2, and cerium oxide sulfide are present to improve machinability but can have the opposite effect, so they often contribute to the process of adhesion. Adhesive wear often occurs in the shape of a cavity near the edge line. The cavity undermines the edge and causes chipping. Chipping reduces the tool life and is challenging to predict, complicating unmanned production and leading to a negative economic output. The negative effect of adhesion can be reduced by providing lubrication, oil, or other coolant droplets, between the cutting tool and the chip or work. Cutting speed significantly affects wear and tool life, while topography and textures on the tool can also affect wear and wear rate.

Experimental tests found that a smooth surface generates less adhesive wear and fewer deposits on the cutting tool and the workpiece. This part of the adhesion is not fully understood, a rough surface gives rise to a more powerful adhesion, and the surface created after an adhesive “rip off” is more attractive than the surface nearby.

A typical adhesive wear pattern is one or more cavities’ looking like caries in a tooth. Three-body adhesive wear occurs when two solids slide with a semi-liquid substance in between. The strong bonding between the semi-liquid substances and the cutting tool is central to the adhesion process. Later, this bond will be ripped apart, taking a piece of the cutting tool. The bond is regarded as a result of a chemical reaction and not as a welding zone with melted parts joined together.

Read the complete article on ResearchGate (open access) here. => (PDF) Exploring the mechanics of adhesion in metal cutting (researchgate.net)

This article was produced by Kourosh Tatar and Inge Svenningsson.