Failure of cemented carbide tools in intermittent cutting

Some observations on wear and damages in cemented carbide tools

“…The result is a lower percentage reduction in tool temperature during the idle period, which leads to a reduction in the number of thermal cracks. These findings, however, disagree with those of Bhatia et al (1979), who observed an increase in ∆T when the feed rate was increased during interrupted cutting. Melo (2001) explains that thermal stresses generated at the cutting edges of the tools are more severe when higher feed rates are used due to the increase of the temperature ∆T.…”

“…Melo (2001) explains that thermal stresses generated at the cutting edges of the tools are more severe when higher feed rates are used due to the increase of the temperature ∆T. An explanation for cases where an increase in feed rate did not conspicuously increase the number of thermal cracks is that an increase in the feed rate increases ∆T (Bhatia et al, 1979) but also reduces the number of thermo-mechanical cycles (number of idle and cutting periods) for the same cutting length, thus reducing the risk of thermal cracking. Thus, the system must be evaluated considering both these effects.…”

Evolution of residual stress in Ti–Al–Ta–N coatings on hard metal milling inserts

“…This local plastic deformation is introduced by thermal stress amplitudes, induced by frictional heating [7], which initiate the nucleation and growth of combcracks [2,7]. At the present cutting temperature a combination of thermal stresses and sufficiently high load stresses can exceed the flow stress of a tool material and provoke the buildup of tensile residual stress close to the cutting edge upon cooling.…”

The performance of polycrystalline cubic boron nitride tools in continuous, semi-interrupted, and interrupted hard machining

“…[2,8]. Research to date on interrupted cutting has focused on a number of areas such as brittle fracture [9], interrupt geometry [10][11][12] and cutting speed, interrupt frequency, and workpiece microstructural effects [13,14]. It has been found that low-CBN grades exhibit increased flank wear when higher interrupt frequencies are used, while high-CBN grades are less sensitive to the interrupts but wear rapidly at higher cutting speeds [13,14].…”