Laser powder deposition of carbon nanotube reinforced nickel-based superalloy Inconel 718

Abstract

Electroless Ni-P coating was plated on the surface of multi-walled carbon nanotubes (MWCNTs). The Ni-P coated carbon nanotubes (NiPCNTs) were dispersed into Inconel 718 (IN718) powder by ball milling. Then the powder mixtures were deposited into the IN718/NiPCNTs composite coatings by laser powder deposition process. The survivability of MWCNTs, susceptibility to heat affected zone (HAZ) liquation cracking and tensile mechanical properties of the coatings were studied. The results showed that the MWCNTs were successfully incorporated into the IN718 coatings but most of them were transformed into the porous carbon nano ribbons (CNRs), graphene nano sheets (GNSs) and diamond-like nano particles (DNPs). The CNRs were resulted by the inter-welding of the MWCNTs and GNSs. Large thin CNRs bridging with the Laves particles and interdendritically bonded regions improved the stress transfer across the interdendritic regions. The stress localized on the last remaining liquation film could be depressed and the susceptibility to HAZ liquation cracking was suppressed. Furthermore, the tensile strength of the IN718/NiPCNTs coatings was increased significantly whereas the ductility of the coatings was somewhat reduced, which was attributed not only to the addition of the carbon nano allotropes but also the increased formation of the hard but brittle Laves phase.