Metallic laser clad coatings: on the processing-microstructure-property relationships

摘要

A thick metallic coating that is resistant against high loading impact, severe wear and corrosion at high temperatures can be produced through the laser clad method. This work introduces the Orientation Imagining Microscopy based on electron backscatter diffraction in a scanning electron microscope as a very powerful instrument for studying relationships between processing parameters and the microstructure of individual laser tracks and final coatings formed by overlap. The study has been performed on thick (～1mm) Co-based coatings prepared by a 2 kW CW Nd:YAG laser cladding on 42CrMo4 steel substrate using substantially different laser beam scanning speeds. OIM provides new insights into the microstructure of laser clad coatings and yields very useful information concerning the directional grow of individual grains, the solidification texture and the shape of solidification front during laser cladding. Strong correlations between these parameters and laser cladding speed as well as the presence of internal interfaces with the sharp microstructural and mechanical properties changes are presented and discussed.