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S390粉末高速钢经1180℃真空加热气冷(4×105Pa)、1230℃真空加热气冷(6×105Pa)后得到以下贝氏体为主的显微组织。结果表明,在片状下贝氏体中部析出成排碳化物是碳按下坡扩散机制和按dr/dt∝t-1/2方程长成260 nm×65 nm椭球状。在残留合金碳化物边缘析出纳米椭球状碳化物是按碳上坡扩散在离碳化物某处形成碳浓度峰,并处于最大过冷条件下进行析出的机制。
S390 powder high-speed steel was heated at 1180 ℃ under vacuum heating (4 × 105Pa), 1230 ℃ under vacuum heating (6 × 105Pa) to obtain the following bainite-based microstructure. The results show that in the middle of the sheet-like lower bainite, carbides are precipitated into rows of carbides, which are characterized by descending diffusion mechanism of carbon and 260 × 65 nm ellipsoids according to the equation dr / dtαt-1/2. The precipitation of nano-ellipsoidal carbides at the edge of the residual alloy carbides is a mechanism in which carbon is diffused up to a carbon concentration peak somewhere away from the carbide and is precipitated under the maximum supercooling conditions.