Rolling Contact Fatigue of Upper and Lower Bainitic Spheroidal Graphite Cast Iron

Abstract

  Spheroidal graphite cast iron containing 3.61%C, 2.21%Si, 0.4%Mn and 0.045%Mg were austempered at 375°C and 235°C for 2hr. The rolling contact fatigue strength of austempered cast iron was investigated by using a Nishihara-type rolling contact testing machine under a light oil lubricant, and the effects of bainite structures and relative sliding ratio on the rolling contact fatigue limit (F^*) were studied. F^* of lower bainitic spheroidal graphite cast iron was larger than that of upper bainitic iron, though the former worn and the surface rougher during rolling contact test. F^* of the both lower and upper bainitic irons became smaller as the relative sliding ratio increased.