20钢铸铁浴渗碳渗层组织的分析

本文探讨了20钢在铸铁浴中经不同温度及时间渗碳的渗层组织。结果表明，试样在1270℃的铸铁浴中保留30秒，距表面130－150μm处，其渗层组织为渗碳体＋珠光体＋铁素体；试样在1300℃的铸铁浴中保留30秒，距表面0－120μm处，其渗层组织为渗碳体＋珠光体，且在基体上形成棒条状的碳化物。     

Application of the method of thermo-EMF for checking the carburized layer in steel

The physicochemical processes entailed in carburization are distinguished by their complexity and instability. When such treatment is to be carried out under industrial conditions, it requires operative information on the distribution of the diffusing element across the metallic layer that is being saturated. This information is particularly important in automated technological processes. Timely correction of the technological parameters of carburization helps attain a stabler level of the strength properties of the treated components. The article suggests a method of checking the distribution of carbon across the carburized layer in steel by measurement of the thermo-emf. It presents the results of investigations of the steels 12KhN3A, 20Kh2N4A, 18KhGT after different kinds of heat treatment. The accuracy of determining the carbon content of the layer is not poorer than 0.08%.Donbass Mining and Metallurgical Institute. Stakhanov Engineering Works. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3. pp. 12–15, March, 1994.     

23Si2MnCrNiMoV钢固体渗碳层的影响因素

研究了渗碳温度、渗碳时间、扩散时间、深冷处理参数对23Si2Mn Cr Ni Mo V钢渗碳层的碳浓度梯度、表层低硬度区深度、有效渗硬层深度(550 HV0.3)、碳扩散距离、微观组织形貌等影响,实验研究的渗碳温度区间为890~970℃,渗碳时间为4~10 h,扩散时间为0~4 h。结果表明,较多的残留奥氏体存在是造成渗碳表层高C低硬度的主要原因,控制C浓度为0.72%~0.86%时,可获得最大硬度,若进一步增加C含量,会形成大量的残留奥氏体,反而降低渗透层的硬度;深冷处理对有效渗硬层深度几乎没有影响,但可使表层低硬度区域从距表面0.7 mm缩至0.3 mm。     

On the formation of the structure of a carburized layer during cementation of a low-carbon martensitic steel 12Kh2G2NMFT

The process of production and subsequent strengthening of a gradient carburized layer on a low-carbon martensitic steel 12Kh2G2NMFT has been investigated. It has been shown that the structure and properties of the carburized layer and of the base of the steel can be optimized by quenching from the intercritical temperature range after a preheating or high-temperature tempering. In the carburized layer, reverted austenite with a high hardness equal to or even exceeding the hardness of martensite has been obtained. The strengthening of the austenite occurs due to the precipitation of dispersed carbides during heat treatment following cementation.     

A model of diffusion growth of carbide-phase particles in the carburized layer of heat-resistant steels

A mathematical model of carburization of a complexly alloyed heat-resistant steel is suggested for predicting the chemical and phase composition and structure of diffusion layers that allows for formation of particles of the excess carbide phase in the carburization process. A computer-aided solution of the set of nonlinear equations makes it possible to compute the distribution of the carbon concentration, the volume fraction of the carbide phase, and the distribution of its particles over the thickness of the diffusion layer. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 26–30, September, 1998.     

TA2钛板掺杂钒离子渗碳层的耐腐蚀性能

为提高钛基双极板的耐腐蚀性能和导电性,在TA2纯钛的表面进行双辉离子渗碳,另外为降低渗碳温度,在渗碳过程中掺杂钒。使用扫描电镜和能谱分析、X射线衍射对改性层的组织结构、化学成分、物相组成进行研究,并测得改性层的界面接触电阻率、耐腐蚀性能。结果表明,在优化的制备工艺参数下,在TA2表面生成结构致密的TiC改性层、钒掺杂渗碳改性层。当压实力为140 N/cm²时,730℃下制备的钒掺杂渗碳改性层、850℃下制备的TiC改性层、TA2基体的界面接触电阻率分别是1.17、3.66、14.71 mΩ/cm²。在模拟双极板的工作环境中,测得730℃下制备的钒掺杂渗碳改性层、850℃下制备的TiC改性层的自腐蚀电流密度分别是5.238、7.563μA/cm²,均比TA2基体的腐蚀电流密度低1个数量级。在离子渗碳的过程中掺杂钒可以有效降低渗碳的工艺温度,并且提高TA2基体的导电性和耐腐蚀性能。     

预渗氮处理对20CrMnTi钢真空渗碳层耐蚀性能的影响

在真空渗碳前预先对20CrMnTi钢进行真空渗氮处理,采用OM、SEM和XRD研究了预渗氮处理对渗碳层显微组织及腐蚀形貌的影响,通过电化学测试和浸泡腐蚀质量损失来评价其耐蚀性能。结果表明,经过预渗氮处理的渗碳试样的渗层马氏体更加细小并且有大量渗碳体析出,耐腐蚀性明显提高,自腐蚀电流密度从1.3608×10^-5 mA·cm^-2下降到2.9817×10^-6 mA·cm^-2,自腐蚀电位由-0.7741 V提高到了-0.6672 V,其腐蚀速率和发生腐蚀的倾向大大降低,并且由质量损失得出的腐蚀速率仅为渗碳试样的一半。这主要是由于预渗氮+渗碳处理试样渗层细小的马氏体组织和渗碳体在腐蚀时会阻碍孔蚀的扩展从而降低腐蚀速率,并且渗层的氮原子会与溶液发生化学反应生成NH⁺₄及NO^-₂或NO^-₃,降低Cl^-对材料的腐蚀作用。     

渗碳方式对18CrNi4A钢齿轮渗层的影响

对18CrNi4A钢齿轮试件分别采取可控气氛和低压真空两种方式进行渗碳,研究了渗碳方式对齿轮渗碳层组织的影响。结果表明,在齿高中部有效硬化层深度相近的情况下,与可控气氛渗碳相比,低压真空渗碳处理的齿根圆角处有效硬化层深度显著增加。采取低压真空渗碳处理的齿轮,渗层中碳化物呈细小、弥散分布,而传统可控气氛渗碳处理的齿轮碳化物较粗大。     

沉淀硬化不锈钢表面低温等离子渗碳层组织结构和性能

本研究对15-5PH和17-4PH沉淀硬化不锈钢进行了460 ℃等离子体渗碳处理。利用金相观察、X射线衍射分析对渗碳层组织和相结构进行表征,采用显微硬度计测量渗碳层的硬度,通过极化曲线研究渗碳层在3.5 wt% NaCl溶液中的耐蚀性能。结果表明,经等离子渗碳后,15-5PH和17-4PH不锈钢表面均形成了“双层”组织,渗层主要由含碳“膨胀”马氏体α′_C和少量Fe₃C相组成,渗碳后不锈钢硬度均显著提高。在本试验条件下,渗碳后不锈钢试样的耐蚀性均略有下降,其中15-5PH和17-4PH不锈钢,随着渗碳时间增加,耐蚀性均没有明显变化,而随着渗层深度的增加,15-5PH不锈钢表面渗碳层的耐蚀性逐渐变差;而17-4PH不锈钢表面渗碳层的耐蚀性先增加后降低。