Contact fatigue behavior of a-Al2O3-Ti(C,N) CVD coated WC-Co under dry and wet conditions

Abstract

The response to cycling contact fatigue load of a WC-6%Co carbide coated with a Ti(C,N)/a-Al2O3 CVD multilayer was investigated in dry and wet conditions. Imprints in dry conditions were characterized by small thin cracks forming a circumference at the maximum radii of the imprint. The damaged coating was totally present in the final imprint of the dry test. Wet indentations showcase an area in the imprint where the a-Al2O3 layer has been removed throughout a ring but was kept at the center of the indentation, suggesting that the coating damage under cycling contact load in wet conditions is dominated by a-Al2O3 degradation, associated with a fretting effect or tangential loads accelerating the fatigue-corrosion of the alumina layer.