Fabrication of coatings and powders of refractory metals by carbonyl method and their properties

Papers on Cr, Mo, W carbonyl coating deposition on powders with particle sizes from ∼ 1 μm to hundreds of microns from different materials reviewed. The best results are obtained during the fluidized bed processes. The coatings are uniform following the shape of particles. It is established that refractory coatings, obtaned as a result of thermal dissociation of W and Mo carbonyls at temperatures close to the onset of decomposition, consist of metastable carbides with fcc lattice. The process of refractory metal powder fabrication with the help of installation designed by the authors is described. It is marked that carbonyl powder properties take essentially effect on the following characteristics: temperature of decomposition instrument, quantity of carbonyl vapor applied, the origin and flow rate of gas-carrier. Mo, Cr carbonyl powders even highly dispersed are not pyrophoric. The conclusion about serious advantages and great practical applicabilities of the carbonyl method for gas-phase obtaining coatings and powders of refractory metals in some fields of industry has been made