Experimental observations of contact fatigue crack mechanisms for austempered ductile iron (ADI) discs

Collected from several twin-disc contact fatigue tests, images concerning crack development at ADI surfaces and sub-surfaces are presented. Several auxiliary surface analysis techniques were used (electronic scanning microscopy, video imaging and perfilometry). Defects found at these ADI samples are characterised and related to operating conditions. Elastohydrodinamic theory was used to evaluate surface tribological performance, involving parameters such as lubrication, roughness and general operating conditions. Results concerning a quick procedure to allow the evaluation of fatigue resistance properties among different ADI sample discs are also presented.