Materials Science and Engineering, 78 (1986) 127-134 127 Abrasion Mechanisms of White Cast Iron II: Influence of the Metallurgical Structure of V-Cr White Cast Irons J. D. B. DE MELLO* and M. DURAND-CHARRE Institut Polytechnique de Grenoble, Ecole Nationale Sup~rieure d'Electrochimie et d'Electromdtallurgie de Grenoble, Laboratoire de Thermodynamique et Physico-chimie M~tallurgiques, Laboratoire associ~ au CNRS 29, B.P. 75, Domaine Universitaire, 38402 Saint Martin D'Hdres (France) T. MATHIA Ecole Centrale de Lyon, Laboratoire de Technologie des Surfaces, Unit~e associ~e au CNRS 855, B.P. 163, 69130 Ecully C~dex (France) (Received July 31, 1984; in revised form July 16, 1985) ABSTRACT A series of five alloys containing up to 10 wt. % Cr and 6 wt. % V was investigated. The metallurgical structure was determined and the amounts of the carbides M7Cs and V8C5 were measured. Three-body abrasion experi- ments were carried out in order to determine the wear rate. The topographical states of the abraded surfaces were then characterized at different stages of the abrasive process. It was established that, when the size of the vana- dium carbides was taken into account, these carbides provide a better protection against wear than do the chromium MTCz carbides. In addition, the role of the coarseness of the metallurgical structure is discussed. 1. INTRODUCTION The object of the study in Part I [1] was the abrasion behaviour of Cr-Mo white cast iron. These alloys have a good wear resistance essentially on account of the presence of so- lidification hard carbides. A correlation was established [ 1 ] between the wear resistance and the global carbide content. The results are summarized in Fig. 1. It appears that the high- est wear resistance occurs with a composition close to the eutectic composition with about 30 vol.% of carbides. Usually a linear [1] rela- *Present address: Departamento Fisica e Materiai's, Universidade Federal de Uberlandia, Campus Santa Monica, Uberlandia MG, Brazil. tion between abrasion resistance and the amount of carbides is involved. In Fig. 1, the correlation is not so straightforward. In effect, for hypoeutectic compositions the wear rate decreases as the amount of carbides increases. However, the wear rate again increases with the amount of carbides for hypereutectic com- Au(r 8oi 60. 40. Ig h'lcm -2) L-- \ / 1 g 5 T o lb 2'o 3'o ~o K(%~ Fig. 1. Main characteristic features of Cr-Mo white cast iron (wear rate AU; volumetric amount K of car- bide; Pearson's coefficient ~2; Fisher's coefficient 71) [1]: alloy 1, 3.12 ~2 ~< 6.34, 1.03 < 71 < 0.86; atloy 9, 3.30 </~2 ~ 5.23, 0.63 < 71 < 0.31;alloy 5, 3.39 < ~2 < 5.34, 0.60 < 71 < 0.44. 0025-5416/86/$3.50 © Elsevier Sequoia/Printed in The Netherlands