FORMATION OF AN ADHERENT LAYER ON A CUTTING-TOOL STUDIED BY MICROMACHINING AND FINITE-ELEMENT ANALYSIS

In order to clarify further the formation of an adherent layer on a cu tting tool when machining a calcium deoxidized low sulphur content aus tenitic free machining stainless steel, the deformation and crack prop agation around inclusions were monitored dynamically using a microcutt ing device in a scanning electron microscope. The temperature distribu tion field within a cutting tool under conditions of adherent layer fo rmation was determined using the finite element method. It was observe d that in the chip secondary shear zone, cracks around inclusions tend ed to propagate to the edge of the chip which allowed the inclusions t o extrude onto the cutting tool surface. These extended inclusions for med an adhered layer on the cutting tool surface which was analysed us ing energy-dispersive analysis of X-rays. It was found that the temper ature gradient in the cutting tool from the tool face at a position 0. 25 to 0.5 mm from the major cutting edge is much smaller in the presen ce of an adhered layer than without an adhered layer. A stable adhered layer formed on the tool was associated with a constant tool face tem perature in the region of 850 degrees C. The results of the present in vestigation support the mechanism of adherent layer formation proposed previously. (C) Elsevier Science S.A.