Surface initiated rolling/sliding contact fatigue in pearlitic and low/medium carbon bainitic steels

A study of surface initiated rolling/sliding contact fatigue (RCF) behavior of two pearlitic and four low/medium carbon bainitic steels has focused on three aspects; RCF performance as a function of contact pressure, failure mechanisms, and ratchetting strain behavior including the effect of slide/roll ratio.;A contact pressure range of 858 to 2300 MPa, water lubrication and a slide/roll ratio of 10% were used to establish RCF life. The relationship between rolling contact fatigue life and contact pressure is non-linear. The relative performance of the steels is consistent with their mechanical properties, with longer RCF life being associated with higher strength irrespective of microstructure. The six steels tested exhibited very similar RCF resistance as a function of normalized contact pressure, P;Two distinct crack growth modes have been identified. The shear band cracking mode, which is associated with the severely deformed surface layer, predominates above the theoretical shakedown limit of P;Ratchetting strain data of a pearlitic steel are a non-linear function of both contact pressure and the number of contact cycles. The most important feature of the non-linearity is its asymptotic strain rate behavior. A critical strain concept for crack initiation has been proposed. The variation in ratchetting strain consistently reflected the variation in tangential to normal traction ratios (T/N) at different slide/roll ratios, with a higher strain for higher (T/N) and convergence in strain rate corresponding to convergence in (T/N) ratios as contact cycles increased. The variation in TM values is partially attributed to the influence of sliding distance on the coefficient of friction through building up a stable contact interface, and a stick-slip phenomenon involved at slide/roll ratios...