Study on the element segregation and crystal growth behavior of carbon nanotube reinforced IN718 alloy fabricated by laser cladding

Abstract

Electroless plating of Ni was pre-treated on the surface of carbon nanotubes (CNTs). And then, laser cladding of CNTs reinforced nickel-based superalloy IN718 was manufactured. The structural evolution of CNTs was studied and the results showed that, attributed to the high energy laser beam irradiation and high-temperature molten pool heat effect, the tubular structure of CNTs can be opened up, forming the granene nanosheets (GNSs); the tubular structure of CNTs can also be collapsed and inter-bonded with the neighbouring CNTs and GNSs, forming the large scale of carbon nanoribbons; and the GNSs can also be curled up, forming the diamond-like nanoparticles. It is found that with the increase of the Ni deposition thickness on the CNTs surface, the structural integrity of CNTs can be improved. The effect of CNTs addition on the element segregation and dendritic crystal growth behavior of IN718 superalloy was further studied. The results showed that with the addition of Ni0.5CNTs (i.e. Ni-coated CNTs with 99.5 wt. % Ni thickness), the element segregation of IN718 superalloy can be depressed dramatically and as a result, the interdendritic low melting Laves phase formation can be suppressed.