a b s t r a c tIn machining processes, surface roughness and dimensional accuracy of machined parts depend on tool wear. Cemented carbide based cutting tools remain widely used in machining processes for their wear resistance. The aim of this paper is to study wear mechanisms of a WC-Co cutting tool grade under tribological conditions. Dry friction experiments are carried out on a high-speed pin-on-disc tribometer considering WC-Co pins against steel discs made of an AISI 1045 grade. Furthermore, two type-K thermocouples are embedded in WC-Co pins in order to estimate the contact temperature during sliding tests. A large sliding speed range is considered: from 60 up to 600 m/min. Results deal with wear rate versus tribological conditions, evolution of friction coefficient and temperature versus sliding speed and evolution of wear mechanisms. WC-Co tribological pins exhibit different wear mechanisms: abrasion, adhesion, transgranular WC micro-cracking and WC/WC debonding. Circulation of debris in the friction contact depends on sliding speed and on test duration. The evolution of surface temperature versus friction coefficient is studied too. Furthermore, a particular attention is paid on the relationship between the thermal energy in the pin and the mechanical energy in the contact. The thermal energy is calculated from the temperature values of K-thermocouples and the mechanical energy dissipated in the pin is calculated from friction coefficient evolutions. Relationships are established through modelling approaches.

This original study investigates the damages of WC-6Co uncoated carbide tools during dry turning of AISI 1045 steel at mean and high speeds. The different wear micromechanisms are explained on the basis of different microstructural observations and analyses made by different techniques: (i) optical microscopy (OM) at macro-scale, (ii) scanning electron microscopy (SEM), with back-scattered electron imaging (BSE) at micro-scale, (iii) energy dispersive spectroscopy (EDS), X ray mapping with wavelength dispersive spectroscopy (WDS) for the chemical analyses and (iv) temperature evolution during machining. We noted that at conventional cutting speed Vc ≤ 250 m/min, normal cutting tool wear types (adhesion, abrasion and built up edge) are clearly observed. However, for cutting speed Vc N 250 m/min a severe wear is observed because the behavior of the WC-6Co grade completely changes due to a severe thermomechanical loading. Through all SEM micrographs, it is observed that this severe wear consists of several steps as: excessive deformation of WC-6Co bulk material and binder phase (Co), deformation and intragranular microcracking of WC, WC grain fragmentation and production of WC fragments in the tool/chip contact. Thus, the WC fragments accumulated at the tool/chip interface cause abrasion phenomena and pullout WC from tool surface. WC fragments contribute also to the microcutting and microploughing of chips, which lead to form a transferred layer at the tool rake face. Finally, based on the observations of the different wear micromechanisms, a scenario of WC-6Co damages is proposed through to a phenomenological model.

In machining, it is clearly noticed that the cutting tool wear influences the cutting process. However, it is difficult with experimental methods to study the effects of tool wear on several machining variables. Thus, in the literature, some earlier studies are performed separately on the effect of tool flank wear and crater wear on cutting process variables (such as cutting forces and temperature). Furthermore when the workpiece material adheres in cutting tool, it affects considerably the heat transfer phenomena. Accordingly, in this work the finite element analysis (FEA) is performed to investigate the influence of combination of tool flank and crater wear on the local or global variables such as cutting forces, tool temperature, chip formation on the one hand and the effects of the oxidized adhesion layer considered as oxide (Fe 2 O 3 /Fe 3 O 4 /FeO) on the heat transfer in cutting insert on the other hand. In this investigation, an uncoated cutting insert WC-6Co and medium carbon steel grade AISI 1045 are used. The factorial experimental design technique with three parameters (cutting speed Vc, flank wear land VB, crater wear depth KT) is used for the first investigation without adhesion layer. Then, only linear investigation is performed. The analysis has shown the influence of the different configurations of the tool wear geometry on the local or global cutting process variables, mainly on temperature and cutting. The simulation's results show also, the highly influence of the oxidized adhesion layer (oxide Fe 2 O 3 / Fe 3 O 4 /FeO) on the heat transfer.

Cemented carbide based cutting tools remain widely used in machining processes for their wear resistance. Knowledge and modelling of wear processes are of prior importance to get models to predict and increase the cutting tool service life. The present paper deals with some results of a research work that study relationships between wear and temperature in the case of pin-on-disc tribological experiments. Topic of the paper is focussed on the estimation of the pin/disc contact temperature by coupling experimental measurements and computational methods.Friction experiments are conducted with WC-6Co pins against steel discs made of an AISI 1045 grade. Furthermore, WC-6Co pins are instrumented with two type-K thermocouples. A large sliding velocity range is considered in the study: from 100m/min up to 600m/min. The present paper is focussed on the 600m/min velocity. During these tribological tests, tangential forces and thermocouple temperatures are measured and monitored. From these values, the heat flux in the WC-6Co pin is estimated by two different ways. On one hand by considering the unidirectional Fourier law, on the other hand by estimating the heat partition coefficient [1] between the disc and the pin. The heat partition coefficient is determined from a physical approach based on the consideration of the mechanical power dissipated in the contact. In both cases, the heat transfer in the pin is then modelled by finite element methods. It is necessary to perform numerical analysis to estimate the pin/disc interface temperature because of the impossibility to measure it directly during friction tests. Results of experiments and of numerical simulations are compared.142 Friction at high sliding speed of WC-6Co pin versus steel disc AISI 1045: estimation of the contact temperature