Microstructure, microsegregation and nanohardness of CMT clad layers of Ni-base alloy on 16Mo3 steel

Highlights: • MX particles and Laves phases in Ni-based superalloy were investigated. • MX particles and Laves phases were located in the internedritic region. • MX consisting of a (Nb, Ti)C,N core surrounded by (Nb, Ti)N shell. • The strong segregation of Mo and Nb to the interdendritic region was found. • New solidification path is propose. Microstructure and properties of Inconel 625 coatings deposited by the Cold Metal Transfer technique on a 16Mo3 boiler tube were investigated. The clad layers were shown to have a typical cellular-dendritic structure with secondary phases in the interdendritic regions (e.g. Laves phases and complex nitrides/carbides (MX)). Nanohardness of the interdendritic regions was higher than of the matrix dendritic regions. Energy dispersive X-ray spectroscopy analysis revealed microsegregation of Ni, Cr, Fe to the dendritic regions, as well as interdendritic segregation of Nb and Mo. Based on the phase identifications performed, a new solidification path is proposed.