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The softening of cemented carbide at the elevated temperature of MTCVD processes results in significant reduction of their strength, and thus, high coating deformation during cutting. In this way, at interrupted cutting loads, as during turning cast iron, the cutting performance of MTCVD coated cemented carbide inserts degrades due to premature coating fatigue fracture. To overcome this problem, appropriate heat treatments of MTCVD coated inserts were conducted. The related temperatures and durations for improving the substrate properties were optimized considering obtained strength data of uncoated inserts variously heat treated and the turning performance of coated ones correspondingly heat treated. [ABSTRACT FROM AUTHOR]

Coated cemented carbide inserts with diverse compressive residual stresses in the film structure were manufactured applying different substrate bias voltages. Moreover, a portion of the coated specimens was annealed for eliminating compressive residual stresses. Residual stress measurements, nanoindentations, nano- and inclined-impact tests, as well as FEM-supported calculations were performed for assessing the coating's mechanical properties, cohesion, brittleness and adhesion. Furthermore, the cutting performance of the coated inserts was investigated in turning AISI 1045. According to the attained results, coating residual stresses affect significantly the film properties and wear behavior. Hereupon, a certain residual stress level can be considered as optimum. [ABSTRACT FROM AUTHOR]

Abstract: The wear behaviour of PM-HSS milling inserts is investigated experimentally. Cutting inserts with different cutting edge radii tested in industrial conditions were examined. The radii have been obtained either by micro-sandblasting or by honing. The initiation and progress of the tool wear was analysed with scanning electron microscopy (SEM) of the cutting edges. The experimental results exhibit quantitatively the effect of tool radius on the performance of milling inserts. A radius on the cutting edge prevents fast and unpredictable wear. Moreover, the existence of an optimum value of the radius has been revealed experimentally. In parallel, 2D finite element cutting simulations based on Lagrangian thermo-viscoplastic formulation are used to analyse the tool-stress distributions within the tool coating and substrate. The results obtained from this study provide a fundamental understanding of the cutting mechanics for the coated tool used and can assist in the optimisation of tool edge design. Particularly, the results obtained from the simulations have confirmed that there exists an optimum cutting edge radius that minimizes tool stresses, especially within the coating layer, which seems to be a key factor in the case of milling in dry high speed conditions. [Copyright &y& Elsevier]