Laser Processing of Cast Iron for Enhanced Erosion Resistance
by
Chung-Hsin Chen
Department of Metallurgy and Mining Engineering
Abstract
The surfaces of nodular and pearlitic gray cast iron specimens have been modified by CO2 laser processing for enhanced hardness and erosion resistance. Control of the microstructure was primarily achieved by controlling the processing parameters of laser beam interaction time and power density. The typical laser beam interaction times and power densities used in these experiments were 1.5 sec, 500 kW/cm2 for focused beam laser processing.
Examination of the laser processed near-surface layer showed considerable increase in microhardness and a greatly refined microstructure. Microstructural and microchemical analyses were done using optical microscopy, scanning and x-ray diffraction. There are two kinds of microstructures in the laser hardened layer—a feathery microstructure with a higher hardness (DPH 945 to 1245) and a dendritic microstructure with a lower hardness (DPH 560 to 940).
Erosion testing was done by using a water slurry (Si02 or SiC) abrasive system. Weight loss measurements and erosion crater profiles were used to evaluate erosion resistance of the various microstructures. In general, both ductile and gray cast iron samples showed more quantitative improvement in erosion resistance after laser processing.
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