碳素结构钢高效盐浴渗氮技术研究
发布时间：2019-02-09 20:46
【摘要】：碳素结构钢在工业生产中被广泛应用于制造各种机械零件。但是碳素结构钢硬度低,耐蚀性差,所以需要对碳素结构钢机械零件进行表面处理。目前,盐浴渗氮技术可以显著提高碳素结构钢机械零件的表面硬度,耐磨性和耐蚀性。但是在常规盐浴渗氮温度条件下,渗氮盐浴中分解产生活性氮原子的速率较慢。为了使盐浴渗氮后的零部件获得有效的渗层厚度,就需要显著的增加保温时间,所以常规盐浴渗氮的效率较低。本文采用调质态35钢和45钢为实验材料,探索研究了高温盐浴渗氮、稀土盐浴渗氮和盐浴预氧化的催渗效果和机理。采用金相显微镜(OM)、扫描电子显微镜(SEM)、维氏硬度计、X射线衍射仪(XRD)和电化学工作站等分析仪器对盐浴渗氮处理后试样的截面组织、硬度、物相结构和耐蚀性进行了测试和分析。高温快速盐浴渗氮研究表明,适当提高渗氮温度可以显著缩短盐浴渗氮的保温时间,提高渗氮速度。经660℃×20 min高温盐浴渗氮工艺处理后化合物层厚度与560℃×140 min常规盐浴渗氮基本相同。同时高温盐浴渗氮后化合层与扩散层之间还形成了残余奥氏体层,增加了高温盐浴渗氮处理后样品的耐蚀性。此外,高温盐浴渗氮处理后渗层中还含有γ'-Fe4N相,可以进一步提高渗层的硬度。通过动力学分析,660℃高温盐浴渗氮工艺处理过程中氮原子的扩散系数为27.63×10-14 m2·s-1,是560℃常规盐浴渗氮的10倍以上。同时,相比于常规盐浴渗氮工艺,高温盐浴渗氮工艺处理后活性氮原子的扩散激活能显著降低。稀土盐浴渗氮研究表明,在5 wt.%最佳的稀土添加量条件下,经560℃×120 min稀土盐浴渗氮处理后化合物层厚度为18.5μm,比相同温度和时间的常规盐浴渗氮提高约40%。同时具有更高的截面硬度和耐蚀性。通过XRD和EDS分析表明,稀土盐浴渗氮处理后稀土La原子会渗入到试样表层。此外,EDS分析表明,稀土盐浴渗氮处理后渗层中活性氮原子浓度和扩散的距离均要高于常规盐浴渗氮。盐浴预氧化研究表明,在预氧化温度和时间均为350℃×45 min时,盐浴预氧化+盐浴渗氮处理后的化合物层厚度从空气预氧化+盐浴渗氮的13.2μm增加到20.8μm。同时在相同的预氧化和渗氮工艺参数条件下,盐浴预氧化+盐浴渗氮处理后表面硬度要小于空气预氧化+盐浴渗氮。但是有效硬化层更厚,同时耐蚀性也得到了进一步提高。在相同的预氧化温度和时间的条件下,盐浴预氧化处理后样品表面可以生成更多的Fe3O4相。动力学分析表明,盐浴预氧化工艺处理后的活性氮原子扩散系数提高约2倍。同时,扩散激活能从空气预氧化盐浴渗氮工艺的216 kJ/mol降低到158 kJ/mol。
[Abstract]:Carbon structural steel is widely used in manufacturing various mechanical parts in industrial production. But the hardness of carbon structural steel is low and the corrosion resistance is poor, so it is necessary to treat the mechanical parts of carbon structure steel. At present, salt bath nitriding technology can significantly improve the surface hardness, wear resistance and corrosion resistance of carbon structural steel mechanical parts. However, the rate of decomposition of active nitrogen atoms in nitriding salt bath is slower under conventional salt bath nitriding temperature. In order to obtain effective thickness of nitriding layer after salt bath nitriding, it is necessary to increase the holding time significantly, so the efficiency of conventional salt bath nitriding is low. In this paper, the effect and mechanism of high temperature salt bath nitriding, rare earth salt bath nitriding and salt bath preoxidation were studied by using tempered 35 steel and 45 steel as experimental materials. (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD) and electrochemical workstation were used to analyze the microstructure and hardness of the samples after nitriding in salt bath. The phase structure and corrosion resistance were tested and analyzed. The research of high temperature and fast salt bath nitriding shows that proper increase of nitriding temperature can significantly shorten the holding time of salt bath nitriding and increase the nitriding speed. The thickness of compound layer treated by high temperature salt bath nitriding at 660 鈩，
本文编号：2419377
[Abstract]:Carbon structural steel is widely used in manufacturing various mechanical parts in industrial production. But the hardness of carbon structural steel is low and the corrosion resistance is poor, so it is necessary to treat the mechanical parts of carbon structure steel. At present, salt bath nitriding technology can significantly improve the surface hardness, wear resistance and corrosion resistance of carbon structural steel mechanical parts. However, the rate of decomposition of active nitrogen atoms in nitriding salt bath is slower under conventional salt bath nitriding temperature. In order to obtain effective thickness of nitriding layer after salt bath nitriding, it is necessary to increase the holding time significantly, so the efficiency of conventional salt bath nitriding is low. In this paper, the effect and mechanism of high temperature salt bath nitriding, rare earth salt bath nitriding and salt bath preoxidation were studied by using tempered 35 steel and 45 steel as experimental materials. (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD) and electrochemical workstation were used to analyze the microstructure and hardness of the samples after nitriding in salt bath. The phase structure and corrosion resistance were tested and analyzed. The research of high temperature and fast salt bath nitriding shows that proper increase of nitriding temperature can significantly shorten the holding time of salt bath nitriding and increase the nitriding speed. The thickness of compound layer treated by high temperature salt bath nitriding at 660 鈩，
本文编号：2419377
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