Abstract
Cobalt based Stellite 21 hardfacing layers produced by coaxial CO2 and off-axis HPDL cladding were compared. Properties studied include the temperature of the workpiece, thickness of the heat affected zone (HAZ), dilution, microstructure, hardness and powder catchment efficiency. Both CO2 and HPDL cladding were found to give pore and crack-free coating layers strongly bonded to the substrate. Some inter-run porosity was found from the coating/substrate interface of coating laser-clad with CO2-laser, where as unmelted particle clusters were found in the coating laser-clad with HPDL. Energy dispersive spectroscopy (EDS) studies indicated that only a limited amount of dilution took place in all the coatings. Microhardness values (HV1) were observed to be in the range of 360 - 390 HV1. Due to shorter wavelength of HPDL (808 and 940 nm) beam and used off-axis powder feeding technique in comparison with CO2 laser beam (10.6 um) and coaxial powder feeding technique, heat input into the work piece was higher in HPDL cladding. Coaxial CO2-laser cladding produced excellent, smooth and low roughness, surface quality. HPDL processing parameters need still adjustment to improve coating surface. However, off-axis HPDL cladding showed great potential being 3 - 5 times faster than coaxial CO2-laser cladding depending on the achieved coating thickness.Cobalt based Stellite 21 hardfacing layers produced by coaxial CO2 and off-axis HPDL cladding were compared. Properties studied include the temperature of the workpiece, thickness of the heat affected zone (HAZ), dilution, microstructure, hardness and powder catchment efficiency. Both CO2 and HPDL cladding were found to give pore and crack-free coating layers strongly bonded to the substrate. Some inter-run porosity was found from the coating/substrate interface of coating laser-clad with CO2-laser, where as unmelted particle clusters were found in the coating laser-clad with HPDL. Energy dispersive spectroscopy (EDS) studies indicated that only a limited amount of dilution took place in all the coatings. Microhardness values (HV1) were observed to be in the range of 360 - 390 HV1. Due to shorter wavelength of HPDL (808 and 940 nm) beam and used off-axis powder feeding technique in comparison ...
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