Title: Effect of the microstructure on the tool/chip tribological contact in hard turning of 100Cr6 bearing steel

Authors: Malek Habak, Jean Lou Lebrun, Daniel Badie-Levet

Addresses: Universite de Picardie Jules Verne, LTI, EA 3899, IUT d'Amiens, Avenue des Facultes Le Bailly, Amiens Cedex 1 F-80001, France. ' LPMI/EPPM-EA 1427, ENSAM, 02, Bd du Ronceray, Angers Cedex 1 49035, France. ' LPMI/EPPM-EA 1427, ENSAM, 02, Bd du Ronceray, Angers Cedex 1 49035, France

Abstract: The aims of this study are to explain the phenomena of the primary (ZI) and secondary (ZII) shearing zones formation, generated during machining and to highlight the role of the microstructure of the hardened bearing steel 100Cr6, in frictional contact with a cBN cutting tool. To reproduce the loadings induced during the cutting, dynamic mechanical shearing and tribological tests were carried out: (1) the dynamic shear tests made it possible to reproduce the ZI using |hat-shaped specimens| and (2) the friction phenomenon has been studied using a thermotribometer, to simulate tool–chip contact. In addition, the cutting temperature in orthogonal cutting has also been analysed. Relationships for the microstructure and for the evolution of the friction coefficients as a function of the cutting temperature were obtained. The results show that the absence of carbide has a tendency to decrease the material resistance and the friction coefficient. These evolutions are explained respectively by the higher temperature generated on ZI and ZII.

Keywords: hard turning; machining; microstructure; friction; cutting temperature; tool–chip contact; dynamic shear tests; tribology; bearing steel; mechanical shearing; orthogonal cutting.

DOI: 10.1504/IJMMM.2009.026932

International Journal of Machining and Machinability of Materials, 2009 Vol.6 No.1/2, pp.120 - 138

Published online: 09 Jul 2009 *

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