Abstract The microstructures of the laser hardened layer on the gray cast iron HT20--40 af-ter laser melting processing were examined by optical microscopy, transmission electron microscopy(TEM) and scanning electron microscopy (SEM). Experimental results showed that a structurewith dendritic (M+A') and interdendriticly iaminal transformed ledeburite (M+A'+Fe_3C) wasproduced after laser melting processing. The martensite was a mixture of dislocation martensite andtwin martensite. Dislocation pile-ups and twins were found to exist in the residual austenite.Microsegregation of composition and heterogeneity of microstructure were also apparent after lasermelting processing.
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