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Tchadja Kagnaya
Abstract
Identification of wear mechanisms of a WC-6%Co grade in machining by combining thermal and tribological approaches
Tchadja Kagnaya - 4 September 2009
The aim of this work is to study wear mechanisms of WC-6%Co cutting-tools in machining by turning. Damage modes are controlled by complex damage mechanisms. They combine abrasion, adhesion and diffusion. Furthermore, they are highly dependant of the temperature levels at tool/material interfaces. In the present study two mains approaches are considered: on the one hand machining by turning and on the other hand tribological tests. In both cases temperature measurements and temperature modelling have been performed. Complementary results have been obtained, resulting in a better understanding of wear behaviour between WC-6%Co and a C45 steel grade. Mains wear mechanisms were identified. They deal with:
- large modifications of the WC-6%Co microstructure due to critical mechanical loadings and to high temperature levels (up to 1200°C),
- mobility of WC grains due to the viscoplastic behaviour of the cobalt based binder phase at high temperature. Such a mobility leads to intergranular microcracking phenomena and to WC fragmentation and debonding mechanisms,
- intragranular microcracking and strain phenomena, that can lead to WC grain fragmentation, due to stress concentrations,
- abrasion due to extracted WC fragments and to hard particules extracted from the C45 steel too,
- adhesion, particularly at the end of the contact area between tool and chip.
Key words:
WC-6%Co, machining, turning, tribology, wear, temperature,
contact interfaces, microstructure, damage.