LAUSR

ABSTRACT In this research, the role of Si on the solidification behaviour of NiAl cladding produced by the GTAW process was studied. NiAl and Ni2AlSi compounds were synthesised by mechanical alloying. The produced powders were cladded on the surface of CK45 steel using the GTAW process. Phase evolutions, microstructural changes and fractography of the produced powders as well as the cladded layers were characterised by X-ray diffraction, optical microscopy and scanning electron microscopy methods. After cladding of Ni2AlSi powder mixture, in the first pass of this coating, only NiAl phase and in the second pass, only (Ni,Si)Al intermetallic compounds were formed. For ternary coating, a narrow area including cellular solidification mode was seen at fusion boundary which transformed to equiaxed dendritic solidification mode. Fractography analysis of the claddings revealed that by the addition of Si into NiAl lattice, brittle fracture changed to more ductile fracture with ‘eggcrate-type’ appearance, indicating solidification cracking.