Scuffing and rolling contact fatigue resistance of discrete laser spot hardened austempered ductile iron

Abstract

This study determined the influence of discrete laser spot hardening on the scuffing wear and rolling contact fatigue resistance of Cu-Ni austempered ductile iron (ADI) specimens. The frequency of the single laser pulses were such so as to produce patterns of separated spots, adjacent spots or overlapping spots. Lubricated sliding wear tests were carried out to determine the behaviour of ADI under starved lubrication conditions, usually occurring during the start-up of gears. ADI specimens hardened with adjacent and separated laser spots displayed higher resistance to scuffing than the surfaces treated with overlapping laser spots and the control samples (those tested in the as-austempered condition). Results obtained also show that laser hardening increased the average rolling contact fatigue life over the as-austempered ductile iron specimens. This improved performance was attributed to the higher volume of martensite formed and hence higher surface hardness, and also the residual compressive stresses induced in the laser-treated surfaces. This benefit outweighed the negative effect of the slight roughness induced by the laser treatment.