表面纳米化预处理对316L不锈钢渗氮层摩擦学性能的影响

为改善奥氏体不锈钢的表面硬度和耐磨性,采用超声滚压与离子渗氮复合工艺对316L不锈钢表面进行了表面强化处理。利用扫描电镜(SEM)、硬度计、X射线衍射仪(XRD)和能谱仪以及摩擦磨损试验机等测定了渗氮层的硬度、深度、含氮量和物相组成,研究了表面晶层组织结构对离子渗氮行为和渗氮层在润滑油条件下摩擦学性能的影响。结果表明:直接渗氮和超声滚压/渗氮试样表层组织均由S、γ'、ε和Cr N相组成,渗氮层厚度均为20μm,直接渗氮层以S相为主,超声滚压后渗氮层以ε和γ'相为主,组织结构较为致密;超声滚压/渗氮层的平均渗氮含量是直接渗氮层的2.88倍,摩擦系数降低了0.04,显微硬度和耐磨性是直接渗氮层的1.15倍和2.76倍;超声滚压处理诱使316L不锈钢表面形成的纳米晶层组织结构增强了渗氮试样表面的催渗效能和对渗氮层的支撑强度,超声滚压后渗氮试样的表面耐磨性能最好。     

3Cr2W8V盐浴铬钛复合渗层

本文选用3Cr2WaV在小型井式炉中进行铬钛复合渗实验,应用金相显微镜、扫描电镜、X射线衍射仪、显微硬度计和磨损试验机研究了3Cr2WaV的铬钛复合渗层的组织结构和性能.结果表明,复合渗层表面物相主要有TiN、CrN、(Cr,Fe)2N1-x、(Cr,Fe)7C3和(Cr,Fe)23C6;随渗Ti温度的升高,复合渗层表面显微硬度逐渐提高;复合渗层的耐磨性优于离子渗氮层和渗铬层,但其脆性较大.     

42CrMo钢空气离子氮氧共渗研究

采用不同空气流量对42Cr Mo钢进行离子氮氧共渗,并和常规离子渗氮进行对比。利用金相、显微硬度计、X射线衍射仪、电化学性能分析测试仪对复合渗层的显微组织、厚度、物相、表面硬度及耐蚀性进行了测试和分析。研究结果表明,普通空气可用作42Cr Mo钢离子氮氧共渗处理的氧气源;同样温度和时间条件下,离子氮氧共渗比常规离子渗氮的渗层厚,表面显微硬度提高,硬度梯度更加平缓。同时,渗层中物相含微量Fe3O4,起到提高耐蚀性的效果。同时,研究发现,空气流量0.3 L/min为最佳工艺参数。     

钛铝基合金离子碳氮共渗及其耐磨性的研究

为提高TiAl基合金的耐磨性及抗高温氧化性,利用渗氮在TiAl基合金表面形成氮化物,以提高耐磨性;渗碳形成致密且与基体结合牢固的碳化物层,提高抗高温、抗氧化性;将二者结合,采用辉光离子碳氮共渗的方法,研究了渗层的相结构组成、不同工艺参数对TiAl基合金离子碳氮共渗后渗层厚度以及表面硬度和耐磨性的影响.结果表明:TiAl基合金共渗层是由碳氮化合物层与过渡层组成的复合相结构;随共渗温度的升高和时间的延长,渗层厚度增加;与未经共渗处理的试样相比,表面硬度及耐磨性显著提高.X射线衍射结果显示,渗层主要由TiC,TiN,AlTi3,Al2O3等组成.     

硬化工艺对双辉渗银不锈钢膜层结构及性能的影响

不锈钢双辉渗银处理获得的渗银层硬度较低且不耐磨,因此设计硬化方案对渗银不锈钢进行硬化,以改善其耐磨性。采用等离子氮碳共渗技术进行渗银层的改性工作,对不同工艺下膜层的微观形貌、成分及物相构成进行了分析,并对比了其硬度及磨损性能。两种硬化工艺下测得的硬度及磨损试验数据如下:渗银处理(×3h)+渗氮碳处理(×10h)工艺制备的试样表面硬度值为283HV0.025,15s,平均摩擦系数为0.4287,磨损失重为12.9mg;渗氮碳处理(×10h)+渗银处理(×3h)工艺制备的硬度值为544HV0.025,15s,平均摩擦系数为0.4266,磨损失重为11.5mg。可以看出渗银处理(×3h)+渗氮碳处理(×10h)工艺未提升渗银不锈钢的表面硬度,渗氮碳处理(×10h)+渗银处理(×3h)工艺将渗银不锈钢的表面硬度提升了近1倍。两种硬化工艺对渗银不锈钢的耐磨性能略有改善。     

不锈钢低压真空渗氮组织与性能研究

本文以304奥氏体不锈钢样件为试验研究对象,在8h、400℃、不同气压条件下对样件进行了低压真空离子渗氮试验,研究分析了不同气压下低压真空离子渗氮组织与其性能(离子渗氮后的组织、渗氮层厚度、硬度、耐磨性)的变化,并得出了相应的结论。     

40Cr钢离子氮化与离子镀TiN复合涂层与苜蓿草粉之间的摩擦学特性

在橡胶轮磨料磨损实验机上考察了40Cr钢基体上离子氮化与离子镀TiN复合涂层在苜蓿草粉软磨料下的摩擦学特性。采用划痕法测定了涂层的结合力,利用XRD分析了涂层的相结构,应用扫描电子显微镜观察分析了涂层磨损表面形貌和磨损机理。结果表明:离子氮化与离子镀TiN复合涂层的膜基结合力和硬度均高于TiN涂层;其对于苜蓿草粉软磨料的耐磨性也高于TiN涂层和渗氮层;离子氮化过渡层能显著提高TiN涂层的膜基结合力并改善薄膜的韧性;涂层能有效限制硬质颗粒对基体的压嵌和切削。涂层在苜蓿草粉软磨料下的磨损机制既包括硬质颗粒磨料条件下的切削磨损,也包括软磨料条件下的多次塑性变形和周期疲劳磨损。涂层硬度和韧性的共增可以提高其对软磨料的耐磨性。     

氮势对奥氏体不锈钢离子渗氮性能的影响

对AIS1304奥氏体不锈钢进行了不同氮势的离子渗氮,利用金相显微镜、轮廓仪、摩擦磨损试验机、X射线衍射仪和显微硬度计测试了经渗氮处理后试样改性层的截面形貌、微观结构、相组成和力学性能,并与未渗氮的试样进行了比较。结果表明：随着氮势的增加,试样表面的渗层深度、磨损程度、显微硬度呈规律性变化;X射线衍射分析表明：低氮势容易形成S相,高氮势有利于氮化物的形成。     

TC4钛合金低压真空渗氮处理

为了改善表面性能,对TC4钛合金在不同温度下进行低压真空渗氮处理。采用扫描电子显微镜和X射线衍射分析了渗氮层的组织结构,测试了渗氮层的显微硬度和耐磨性。结果表明,TC4钛合金经低压真空渗氮处理后,可获得由表层Ti N和次表层Ti2Al N组成的改性层。温度较低时,表面形成氮化物数量较少,渗层较薄,硬度较低。随温度升高,氮化物数量增多,渗层厚度增加,硬度及耐磨性也随之增加,温度达820℃时,表面硬度可达1000~1100 HV,硬化层深度为50~60μm。温度继续增加,氮化物聚集长大,渗氮层开始变得疏松,硬度及耐磨性下降。     

20CrMnTi钢碳氮复合强化层的组织与性能北大核心CSCD

为减少氮化时间,降低渗氮层脆性,提高20CrMnTi钢表面的耐磨性能。采用真空脉冲渗碳+(真空脉冲渗氮、真空感应渗氮、离子渗氮)三种方法在20CrMnTi钢表面制备碳氮复合强化层,利用X射线衍射仪、光学显微镜、扫描电镜、能谱仪、EBSD、显微硬度计和微观划痕测试仪等分析了渗层的物相、组织结构、截面元素分布、物相分布、致密性、显微硬度梯度和渗层脆性。结果表明组织从表及里依次为:Fe4N→含氮铁素体→回火索氏体;真空脉冲渗碳+离子渗氮工艺能获得30μm左右硬度值高、致密性好、脆性小的渗氮层,具有良好的耐磨性能;渗层截面中发现次表层含有残留奥氏体呈颗粒状或者细条状弥散的分布在马氏体基体上,奥氏体为软质相,可以较好的吸收外界的冲击力,防止产生和扩展裂纹,有效的降低渗氮层的脆性。先渗碳淬火形成的马氏体在随后的渗氮过程中转变为回火索氏体,碳化物从α-Fe中析出形成的空位,有利于氮原子的吸附和扩散,有效地缩短渗氮时间;先渗碳后渗氮能够有效地降低氮化层的脆性。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。