Thick Co-based coating on cast iron by side laser cladding: Analysis of processing conditions and coating properties

Abstract

The objective of this work was to create Co-based coatings (compositionally close to Stellite 6) on compacted graphite and gray cast iron substrates with a high power laser (2 kW continuous Nd:YAG) cladding process. The relationships between the relevant laser cladding parameters (i.e. laser beam scanning speed, laser power and powder feeding rate) and the main geometrical characteristics of a single laser track (height, width, dilution, etc.) were examined. A gradual variation of a single processing parameter was used for an appropriate experimental analysis and statistical correlations study between main processing parameters and geometrical characteristics of an individual laser track. These relations lead to the design of a laser cladding processing map that can be used as a guideline for the selection and further tuning of proper processing parameters for laser cladding of extensive layer. The coatings with thickness from 1.0 to 3.3 mm were created on flat substrates without cracks and other major defects. The microstructural features of these coatings were studied using optical microscopy, scanning electron microscopy (Philips XL30 FEG), EDS (EDAX) and XRD. Mechanical properties were determined using microhardness measurement, scratch test (CSM Revetest) analysis at room temperature and using the tribotesting (CSM HT Tribometer) at room and elevated (up to 525 °C) temperatures.