Modelling compaction behaviour of nickel-phosphorus and nickel-boron electroless coated titanium powders

Electroless plating is used as an alternative approach to alloying the commercially pure titanium powders. Two types of irregularly shaped powders, which differ in particle size distribution, are coated with nickel-phosphorus (Ni-P) and nickel-boron (Ni-B). A novel method, combining aspects of the Kawakita and Alderbom approaches, has been employed in order to understand compaction behaviour. The overall consolidation is described by a Kawakita-Ludde relationship, and the transition pressures which demarcate the limits of rearrangement only and plastic deformation only are identified using a modification of the Alderborn relationship. A significant increase in green strength is achieved with the Ni-B coated powders, and this is attributed to a modification of friction conditions and the number of possible contacts, which lead to an increased contribution from plastic deformation. The Mohr-Coulomb model and Ohyane equations are used to describe the contribution of the number of contacts on green strength. (C) 2015 Elsevier B.V. All rights reserved