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从热力学和扩散理论上探究了低碳钢气体渗氮氮化势对渗氮化合物层的影响。采用光学显微镜、扫描电镜、X射线衍射仪、电子探针、显微硬度计和电化学分析仪对渗氮层进行表征。结果表明:气体渗氮气氛中的氮化势对化合物层的影响规律随渗氮温度的改变有所不同。当渗氮温度不高于550℃时,高氮化势显著增加化合物层厚度;当渗氮温度不低于580℃时,尽管低氮化势延迟化合物层的形成,但化合物层一旦形成就快速增厚,且其厚度达到甚至超过高氮化势下化合物层的厚度。高氮化势渗氮化合物层中N浓度随深度降低,其最外层N浓度高达10 mass%;低氮化势渗氮化合物层中N浓度分布均匀,大约为5 mass%~6 mass%。高氮化势渗氮化合物层的耐蚀性较好,韧性和致密性较差。低氮化势渗氮化合物层缺陷较少,韧性较高。
From the theory of thermodynamics and diffusion, the influence of gas nitriding potential on the nitriding layer of low carbon steel was explored. The nitrided layer was characterized by optical microscope, scanning electron microscopy, X-ray diffraction, electron probe, microhardness tester and electrochemical analyzer. The results show that the influence of nitriding potential on the compound layer varies with the nitriding temperature. When the nitriding temperature is not higher than 550 ° C, the high nitriding potential significantly increases the thickness of the compound layer; while the nitriding temperature is not lower than 580 ° C, although the low nitriding potential delays the formation of the compound layer, the compound layer once formed rapidly Thickening, and its thickness reaches or exceeds the thickness of the compound layer under high nitriding potential. The concentration of N in the high nitrided potential nitrided compound layer decreases with the depth, and its outermost N concentration is as high as 10 mass%. The N concentration in the low nitrided potential nitrided compound layer is uniformly distributed, ranging from 5 mass% to 6 mass%. High nitride potential nitrided compound layer corrosion resistance is better, less toughness and compactness. Low nitride potential nitriding compound layer less defects, higher toughness.