Sintered composite materials on the basis of Fe/FePO4-coated powders

Composite materials with a network microstructure of -Fe areas surrounded by continuous layer of iron phosphate compounds were prepared on the basis of Fe/FePO4 precipitation coated powder. Spherically shaped particles of this powder were compacted and sintered at 912, 930, 980, 1075 and 1130 degrees C for 3min in air. Sufficiently fast heating rate, rapid formation of a liquid phase and fast cooling suppress the development of diffusion processes and consequently the formation of Fe-Fe metallic connections. Microscopic observations showed that, after appropriate processing conditions, an even and continuous layer, comprising a mixture of ferrous orthophosphate and iron oxide compounds, was achieved. Sintering at 1130 degrees C and fast cooling at similar to 25000 degrees C/min resulted in the formation of a phosphate layer consisting of very fine lamellar structure - graftonite. The phase composition of the phosphate layer was correlated with processing conditions. Corrosion resistance of the sintered composites was measured and related to microstructure and processing technique variants. Copyright (c) 2014 John Wiley & Sons, Ltd.