Assessing the hardness and residual stress at the very edge of a TiAlN coated cutting insert

• A method for determining residual stresses through nanoindentation has been used in order to evaluate the local residual stress in a PVD Ti0.5Al0.5N coating. The influence of residual stress on the measured hardness is obtained by comparing the hardness of as deposited, residually stressed, coating and stress relieved pillars made in the very same coating. The technique offers high lateral resolution, and it can be applied on complex geometries where conventional stress measurements fall short. In this work, the method proved useful for estimating the residual stress at such a complex geometry as a sharp cutting edge. Edges with two different radii were analysed and it was concluded that the nominal residual compressive stress given to a coating can locally, on the very cutting edge, become significantly reduced by elastic relaxation .This effects the cohesion of the coating at that position which, together with the lift-off stress generated at the edge, make the coating in that region especially vulnerable to damage. The experimental results correlated very well with finite element simulations of the residual stress state around cutting edges with the same geometries.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Residual stress

PVD coating

Cutting edge

Nanoindentation

Teknisk fysik med inriktning mot tribomaterial

Engineering Science with specialization in Tribo Materials

Publikations- och innehållstyp

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