Studies on Friction and Transfer Layer Using Inclined En8 Flat and Super Pure Aluminium Pin

Friction influences the nature of transfer layer formed at the interface between tool and metal during sliding. In the present investigation, basic studies were conducted using “Inclined Scratch Test” to understand the mechanism of transfer layer formation during sliding of super pure aluminium pins on EN8 steel flats of different surface roughness under both dry and lubricated conditions. The coefficient of friction, which has two components – the adhesion component and the plowing component, is controlled by the “nature of surface”. It is seen that on surfaces that promotes plan strain conditions near the surface the transfer of material takes place due to the plowing action of the asperities. But, on a surface that promotes plane stress conditions the transfer layer is more due to the adhesion component of friction. It is seen that the adhesion component increases for surfaces that are random in nature but is constant for the other surfaces. The plowing component of friction is highest for the surface that promotes plane strain conditions near the surface. INTRODUCTION Friction plays an important role during sliding and it depends on local contact conditions, such as surface roughness, contact stress, lubrication, and relative speed of the contacting surfaces [1-2]. The understanding of friction is crucial in metal forming operations and is also an important input in simulations [3-7]. Inclined scratch tests have been used to understand the effect of normal load on the failure point of lubricants [8]. The advantage of this test is that the failure load could be obtained from a single experiment. In the present studies inclined scratch is used to study the effect of normal load on the friction force and transfer layer formation during the sliding aluminium alloy pin over EN8 flats. The effect of the surface morphology and lubrication of the EN8 flats on the coefficient of friction and transfer layer formation is studied and the results of these studies are presented