We investigated arc ion-plated Al70Cr30N and Al80Cr20N thin films deposited with three\ndifferent bias voltages (50 V, 100 V, and 150 V) to study crystal phase stabilities, residual stresses,\nand mechanical properties. Commercial compositions of AlxCr100-xN coatings typically range from x\n=50 to 70 where the cubic face centered crystal phase occurs. The present study focuses on films near\nthe solubility limit of Al in the cubic Cr(Al)N lattice around 70 at.%, above which hexagonal AlN\n(h-AlN) starts to form in significant amounts. Residual stress values are obtained by two methods:\ngrazing incidence diffraction with the whole pattern fitting and the conventional side inclination\nmethod (sin2Y method). When multiple phases are present in the film, whole pattern fitting turns\nout to be particularly effective and a comparison of both measurement methods will be discussed.\nThe Al70Cr30N films consist of the cubic phase with crystallite sizes of about 70 nm for all bias\nvoltages. Compressive stress increased with bias voltage from about 3 to almost 6 GPa and coatings\nbecome brittle. Al80Cr20N films showed a different dependence on bias voltage. Using 50 V bias\nvoltage in deposition, the major phase is h-AlN phase with a crystallite grain size of < 30 nm and\n(0002) preferred orientation. With increasing bias the cubic phase is stabilized also reaching about\n70 nm crystallite size. In general, the compressive residual stress was significantly lower than for\nAl70Cr30N films for the same bias voltages which may be a result of the presence of the hexagonal\nphase. Wear and scratch tests confirmed higher ductility of the Al80Cr20N variants but reduced\nresistance of the films in impact wear testing.
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