Influence of the base preheating on cracking of the laser-cladded coatings

摘要

Coatings of stellite SF6 are prepared on the chromium steel base by means of a direct laser cladding. A 1.2 kW CO2 laser is applied and the original material is delivered into the processing zone coaxially with the laser beam. The samples are produced with and without a controlled preheating of the substrate and are investigated by means of metallographic techniques. It is found that the observed micro-cracking susceptibility decreases markedly with increase of the base preheating temperature up to 750 K and the crack-free coatings are produced for preheating around 950 K. The substrate-coating interface reveals a metallic bond and the microstructure is characterized by a fine-grained, dendritic structure. The nearly constant concentration dependence of Fe, Co, Cr and Ni on the distance from interface indicates on homogeneous chemical composition of the produced coatings.