Single layer (specimen) and multi-layer (work piece) coatings, made of CoNiCrAlY alloy powder, deposited by laser cladding
with synchronous feeder on Ni-based superalloy were introduced. Coatings were examined to reveal their
microstructure, phase composition, microhardness and
oxidation resistance using microscope, XRD, micro-hardness tester and high temperature furnace, respectively. The results show that γ-Co, Ni 2Y and Cr 3Ni 2SiC exist in the coatings, and the oxidation products are CoAl 2O 4, Al 2O 3, CoNiO 2, NiCr 2O 4 and CoCr 2O 4. The microstructure is fine in single layer coatings, whereas coarsened structures are observed at the bonding of two tracks and muti-layer coatings because of pre-heating. At the interface, the drendrite growth direction of rapid solidification is found to be perpendicular to the interface. Equiaxed dendritic growth is observed at the remelted bonding area of multi-tracks of single layer and interlayer of multi-layer coatings. The microhardness of coatings is higher than that of the substrate. The oxidation resistance is improved by adding rare earth (Y) that strengthens adhesive force of oxidation products on coating surface. Below 1100 ℃, the oxidation resistance of the coatings is excellent.