Microstructure evolution of grey cast iron powder by high pressure gas atomization

The grey cast iron powders were prepared by high pressure gas atomization. Calculation results show that the cooling rates of droplets of grey cast iron reach to 104 to 106 K s−1 in the experiments. Microstructures of atomized grey cast iron powders with different diameters were characterized by X-ray diffraction, optical microscopy and scanning electron microscopy. Microstructures of powders under 38 μm in diameter are mainly γ-Fe and a little α-Fe. With the increase of powder diameter, content of γ-Fe phase gradually decreases, while content of α-Fe phase increases. When the diameter is over 150 μm, powders are completely composed of α-Fe phase. By measuring the spatial variation in microstructural scales within powders, the results show the lamellar spacing increases with the increase of powder diameter. As the powder size is larger than 106 μm, the increase trend of the lamellar spacing becomes smaller.