Structural characterization of laser-treated Cr3C2-NiCr coatings

The interconnected porosity of the Cr3C2-NiCr coatings obtained by high-vel ocity oxy fuel spraying is detrimental in corrosion and wear resistance app lications. Laser treatments allow sealing of their surfaces through melting and resolidification of a thin superficial laver. A Nd:YAG laser beam was used to irradiate Cr3C2-NiCr coatings either in the continuous wave mode or at different repetition rates in the pulsed one. Results indicated that hi gh peak and low mean laser irradiances are not good, since samples presente d deep grooves and an extensive crack network. At low peak and higher mean laser irradiances the surface was molten, and only a few shallow cracks wer e observed. The interconnected porosity was completely eliminated in a laye r up to 80 mum thick, formed by large Cr7C3 grains imbedded in a NiCr matri x.