| The role of Si on the coarsening behaviors of complex carbide particles precipitated in Cr and Cr-Si steels has been investigated using various quantitative metallographic techniques after spheroidizing over the holding time range 300 to 1800 hours at three different temperatures 650, 680 and 710℃. Most of M₃C type complex carbides precipitated in Cr-Si steel are shown to form along grain boundaries and their average particle sizes appear to be smaller in finer ferrite grains, as compared to those in Cr steel. The value for the slope of each straight line obtained from the relation between the log of average particle size find spheroidizing time is approximately 1/3, which is in agreement with diffusion-controlled growth mechanism. The addition of Si to Cr steel does not change the mode of growth equation for M₃C type complex carbide precipitates Activation energes of 195 KJ mol^(-1) for Cr steel and 227 KJ mol^(-1) for Cr-Si steel are found to give rise to the interdiffusion mechanism of Fe, C, Cr and Si involved in each steel. The experimentally determied particle size distributions approach the steady-state distribution curve as spheroidizing treatment proceeds. The shape of curves, however, shows 3 tendency that the range of particle size distribution is wide with a lowered height of the distribution curve. |
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