Hardening HT20-40 gray cast iron with CO

2

laser

the structures characteristics and forming principle of hardened layer were studied. The results reveal that the laser-hardened zone of HT20-40 gray cast iron is consisted of three layers:(1)melting-chilling layer with whitening structure-refined ledeburite;(2)localized melting layer-graphite part is melted

island structure has the characteristics of casting and martensite;(3)solid transformation layer-very fine martensite

the original pattern of lamellar graphite remains basically. Meanwhile

localized melting layer disappears by proper technology control

and there only exists melting-chilling layer and solid transformation layer.