Wear Behavior of Laser Surface-Hardened Gray and Ductile Cast Irons. Part 2—Erosive Wear

Abstract

A 1.2-kW, continuous wave, CO2 -gas laser was used to transformation harden or melt the surface of gray and ductile cast irons. Effects of surface-hardened layers on solid particle erosion showed that the erosion rate decreased with an increase in surface hardness and case depth. The order of matrix microstructures that increased the erosion rate were ledeburite, tempered martensite, and pearlite. These results were opposite to those observed in bulk-hardened alloys. Erosion mechanisms of brittle, gray iron included micromachining in the untreated condition and grain boundary cracking in the laser-treated condition. In contrast, erosion modes of ductile iron were plastic flow followed by cracking in the untreated condition and platelet formation and fatigue in the laser-treated conditions. The beneficial effects of surface hardening on erosion were examined and discussed.