SURFACE LASER TREATMENT OF DUCTILE IRONS

The effect of the laser surface treatment of three types of ductile iron (Grades 60-40 1 8, 80-55-06 and 100-70 03) was studied. Using a continuous CO2 laser with a square 10 mm x 10 mm beam and uniform power density, the effect of beam scan rate at 2.5 and 5 kW power output was investigated. At each power rate, a range of scan rates was used to produce treatments with and without surface melting. The microstructure and hardness of the different zones of the treated material were analysed. It was found that layers of white iron of the same depth were produced in the three test irons when the operating conditions melted the surface material. Surface porosity can be eliminated by melting, although transverse cracks appeared on the surface with this treatment. Surface martensitic hardening produced a layer of uniform hardness only in the case of the grade 1 00-70-03 ductile iron with a perlitic matrix.