The laser surface-alloying of iron with carbon

Observations are reported on the structure of iron, laser surface-alloyed with carbon. Repeated laser surface-melting of iron pre-coated with DAG graphite has produced layers containing up to 6 wt % C, showing fine-scale white iron structures. Eutectic regions (interlamellar spacing 0.5m) have been shown by transmission electron microscopy to consist of Fe₃C + ferrite, the latter having formed by decomposition of austenite during solid state cooling. Regions of fine pearlite (spacing 55 nm) have also been observed. Carbon diffusion into the substrate during alloying produces a zone containing austenite and martensite.