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摘要: 对Fe–Ni–Cu–C–Mo粉末锻造材料的锻后热处理工艺进行了研究，通过动态连续冷却转变试验绘制出该材料的连续冷却转变（continuous cooling transformation，CCT）曲线，指导材料锻后冷却工艺的选取。对Fe–Ni–Cu–C–Mo淬火试样进行不同温度的低温回火试验，探究不同回火温度对该材料微观组织与力学性能的影响。结果表明，当锻后冷却速率大于7.0 ℃·s−1时，Fe–Ni–Cu–C–Mo粉锻材料组织全为马氏体，硬度趋于稳定；在150 ℃和175 ℃回火，碳化物均匀地分布在马氏体板条内部，起到析出强化的作用，材料表现出优异的抗拉性能。Abstract: The heat treatments of the powder forged Fe‒Ni‒Cu‒C‒Mo materials after forging were studied. The continuous cooling transformation diagram of the powder forged Fe‒Ni‒Cu‒C‒Mo alloys was constructed to guide the selection of cooling process after forging. The quenching Fe‒Ni‒Cu‒C‒Mo specimens were tempered at various temperatures in the low temperature tempering test, and the effects of tempering temperatures on the microstructure and mechanical properties of the Fe‒Ni‒Cu‒C‒Mo materials were investigated. The results show that, when the cooling rate of the Fe–Ni–Cu–C–Mo specimens after forging is more than 7.0 ℃·s−1, the microstructure is the martensite and the hardness tends to be stable. Tempering at 150 and 175 ℃, the carbide is evenly distributed inside the martensite lath, which acts as the precipitation strengthening, and the Fe–Ni–Cu–C–Mo specimens exhibit the excellent tensile properties.
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Key words:
- powder forging /
- gear materials /
- low tempering /
- microstructure /
- mechanical properties
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图 3 动态连续冷却转变试验
Figure 3. Operation scheme of the dynamic continuous cooling transformation test
图 4 升温速率0.1 ℃·s−1的试样膨胀曲线
Figure 4. Expansion curve of the samples with the temperature rising rate of 0.1 ℃·s−1
图 6 粉锻Q61材料不同冷却速率对应的维氏硬度和马氏体体积分数
Figure 6. Vickers hardness and the martensite volume fraction of the powder forged Q61 materials with different cooling rates
图 7 粉锻Q61材料的动态连续冷却转变曲线
Figure 7. Dynamic CCT curves of the powder forged Q61 materials
图 8 粉锻Q61材料不同温度回火后金相组织：（a）150 ℃；（b）175 ℃；（c）200 ℃；（d）225 ℃
Figure 8. Metallographic structures of the powder forged Q61 materials tempered at different temperatures: (a) 150 ℃; (b) 175 ℃; (c) 200 ℃; (d) 225 ℃
图 9 粉锻Q61材料不同温度回火后的扫描电子显微形貌：（a）150 ℃；（b）175 ℃；（c）200 ℃；（d）225 ℃
Figure 9. SEM morphology of the powder forged Q61 materials tempered at different temperatures: (a) 150 ℃; (b) 175 ℃; (c) 200 ℃; (d) 225 ℃
图 11 不同回火温度下粉锻Q61材料力学性能：（a）硬度；（b）强度
Figure 11. Mechanical properties of the powder forged Q61 materials at different tempering temperatures: (a) hardness; (b) strength
图 12 Q61粉锻标准块不同温度回火后的透射电子显微组织：（a）150 ℃；（b）175 ℃；（c）200 ℃；（d）225 ℃
Figure 12. TEM morphology of the powder forged Q61 materials at different tempering temperatures: (a) 150 ℃; (b) 175 ℃; (c) 200 ℃; (d) 225 ℃
表 1 Q61合金粉末化学成分（质量分数）
Table 1. Chemical composition of the Q61 ally powders
% Ni Cu C Mo Fe 1.756 1.00 0.60 0.552 余量 
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表 2 粉锻Q61材料不同冷却速率对应的相变点温度
Table 2. Temperatures at the phase transition points of the powder forged Q61 materials at different cooling rates
冷却速率 / (℃·s−1) A→P开始温度 / ℃ A→P结束温度 / ℃ A→M开始温度 / ℃ A→M结束温度 / ℃ 0.2 575 425 — — 0.5 571 404 — — 0.7 556 387 250 175 1.0 556 385 263 188 2.0 530 374 267 180 3.0 527 360 275 168 5.0 500 462 290 145 7.0 — — 295 157 15.0 — — 313 138 30.0 — — 324 130 50.0 — — 332 138
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