Effects of additions of nickel nanoparticles on sintering response of PM hybrid low alloy steels

Abstract

Addition of pure elements to powder mixes can cause the formation of heterogeneous microstructures in powder metallurgy (PM) parts upon sintering. For instance, it has been shown that additions of nickel particles to an iron powder form nickel rich areas (NRAs), since nickel has low diffusivity in iron at conventional sintering temperature [∼1121°C (2050°F)]. Thus, the present work is aimed at determining if addition of a small quantity of carbon coated nickel nanoparticles to a PM hybrid low alloy steel premix could result in a more homogeneous distribution of nickel in sintered parts. It also characterises the effect of this addition on microstructures and mechanical properties. Grain boundary and volume diffusion coefficients of nickel nanoparticles have been determined using Suzuoka's equation and wavelength dispersive X-ray spectrometry maps. Results show that addition of nanoparticles initiates lattice diffusion at lower temperature and produces less NRA.