CONTACT FATIGUE BEHAVIOR OF AN AUSTENITIC BAINITIC DUCTILE IRON

A Cu-Mo ductile iron was austempered to obtain an austenitic-bainitic matrix. The contact fatigue behaviour of the material with and without laser hardening was tested and compared with that of an induction har dened AISI 1045 steel. The results show that the contact fatigue limit s as obtained from the load-life plot for the ductile iron specimens a re all higher than for steel: those for the laser hardened ductile iro n are 15.9% higher; those for the plain austenitic-bainitic iron are 4 .7% higher. The contact fatigue failure of the austenitic-bainitic iro n was studied. It was found that strain-induced martensite transformat ion occurred during the test. Spherical debris was observed to exist p rior to the failure. It is proposed that the spherical debris was form ed by local melting.