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。     

Ti(CN)/TiC/Al2O3/TiN多层涂层的结构和界面结合力研究

采用中温、高温复合化学气相沉积技术(MHCVD)在WC- (6％wt)Co硬质合金基体表面制备了Ti(CN)/TiC/Al2O3/TiN 多层陶瓷涂层.通过光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)和数显显微硬度计等手段分析多层陶瓷涂层的表面及断面形貌、物相组成、显微硬度;采用表面划痕实验,结合形貌观察及X射线能谱分析(EDS)研究多层陶瓷涂层/硬质合金基体的界面结合力及其影响因素.结果表明:Ti(CN)/TiC/Al2O3/TiN 多层陶瓷涂层结构均匀致密,涂层后硬质合金的显微硬度明显提高,约2600 HV,多层陶瓷涂层与基体界面结合良好,划痕实验显示临界载荷高达105 N,多层陶瓷涂层界面间的原子扩散作用对涂层/基体界面附着力有较大贡献,而涂层内部少量Ti2O3、W6Co6C 等物相的存在对提高界面结合力也有帮助.     

合理使用划痕法及显微法测定TiN薄膜与基体结合力

采用反应磁控溅射的方法在TC4钛合金基板上制备了TiN薄膜,利用划痕法测试了TiN薄膜与基体之间的结合力,并结合薄膜硬度与显微法判断的临界载荷进行了对比分析。结果表明:单纯依靠划痕法判断临界载荷较为局限,结合显微法同时考虑硬度等力学性能共同判断临界载荷,是更为科学合理的办法。     

电弧离子镀与磁控溅射复合技术制备Ti/TiN/TiAlN复合涂层的组织结构与力学性能

采用磁控溅射和电弧离子镀技术,在高速钢基体上制备了Ti/TiN/TiAlN复合涂层。采用扫描电子显微镜、X射线衍射仪、显微硬度计、微米划痕仪等方法研究了镀覆条件对复合涂层的形貌、组织结构和力学性能的影响。结果表明,离子镀镀覆的过渡层对磁控溅射涂层的显微组织和力学性能有重要影响。例如,新开发的AIP+MS技术制备的复合膜比AIP或MS技术制备的薄膜具有更高的硬度、更好的耐磨性能、更光滑的表面和更强的膜基结合力(大于30N)。由于电弧离子镀TiN过渡层表面的"大颗粒"在磁控溅射沉积TiAlN薄膜时也会结晶长大,组织形貌与膜上的TiAlN相似,提高了其与周围薄膜的结合,电弧离子镀TiN过渡层表面的"大颗粒"负面效应大大弱化。     

基于划痕法的高强钢多层氧化皮结合力测试研究

为了测得高强钢多层氧化皮间的结合力,运用划痕试验法对一种高强钢氧化皮进行了划痕试验。基于声发射法和显微观察法获得不同层间剥离的临界载荷,并通过纳米压痕试验获得了不同氧化层及基体的显微硬度。根据上述试验结果计算了氧化层间的结合力以及氧化层与基体基间的结合力,并用拉伸试验法与划痕试验法进行了对比。结果表明:划痕试验法获得的结合力数据具有较高的准确性,高强钢内外氧化层间的结合力约为70MPa,内层氧化层与基体间的结合力约为38 MPa。     

过渡层对TiAlSiN涂层性能的影响

研究不同的过渡层对TiAlSiN涂层结合力和高温抗氧化性的影响。利用划痕仪测定临界载荷,用体视显微镜观察划痕形貌;利用高温热处理炉对试样进行800℃高温抗氧化实验和1200℃淬火实验,并观察宏观形貌;利用X射线衍射仪对涂层进行物相分析。结果表明:基材进行氮化处理对涂层膜基结合力的提升和高温抗氧化性能的提高有一定的加强作用,Cr过渡涂层对涂层膜基结合力和高温抗氧化性能的提高较大,其氧化速率远低于经过氮化处理的锆合金表面涂层的氧化速率,膜基结合力大约33N;通过物相分析,涂层均生成了对应的物相,当氮化剂量达到一定值后,会生成硬度较高的Zr N物相。     

硬质涂层的硬度及结合力的测试方法

本文描述了测定硬质涂层与基体间的结合力和显微硬度的方法和原理,用四点弯曲法、扭转法、划痕法和压痕技术对硬质涂层(TiN和TiC)的结合力进行测定和评价,对显微硬度(也是涂层的重要性能指标)进行评述。     

15-5PH不锈钢基体上硬质膜层制备及性能研究

对比不同的表面处理工艺,选择多弧离子镀方法在15-5 PH不锈钢基材表面制备TiN硬质涂层.分析制备工艺对膜层的表面硬度、膜/基结合强度、膜层结构等基本物理性能的影响,进行工艺优化.结果显示在预热温度高于200℃后,TiN膜层结晶效果较好;负偏压达到600V后,膜／基间“伪扩散”层出现,膜／基结合性能明显提高;工作气压升高,膜层表面硬度、膜／基结合力和沉积速率先升高后下降,分别在4.0,3.0和2.5Pa达到峰值.最终获得的TiN硬质膜层表面硬度大于2000HV0.05,膜／基结合力最小临界载荷高于70N.镀膜处理后,工件的各种性能测试均能满足具体使用要求.     

钛合金表面TiN/CrN纳米多层薄膜的制备及耐磨、耐腐蚀性能

纳米多层涂层在钛合金磨蚀防护领域具有重要应用。本实验采用电弧离子镀膜技术,在TC4钛合金表面制备TiN、CrN及TiN/CrN纳米多层涂层,分别对涂层的微观形貌、相结构、硬度、膜基结合力、摩擦磨损性能和电化学腐蚀性能进行了系统研究。结果表明,TiN/CrN纳米多层涂层沿(111)面择优取向生长,结构致密,调制周期为25 nm,硬度为24 GPa,多层结构打断柱状晶生长,有效阻断腐蚀介质扩散到基体的通道。相较于TiN、CrN涂层,TiN/CrN膜基结合力有显著提高。TiN/CrN涂层磨损率为3.44×10~(-7)mm~3·N~(-1)·m~(-1),自腐蚀电流密度(i_(corr))为3.16×10~(-8)A/cm~2,显著低于TC4及TiN、CrN涂层,说明TiN/CrN纳米多层涂层的耐磨/耐腐蚀性能优于TiN、CrN单层涂层,并能对TC4基体在摩擦腐蚀环境下提供更好的防护。     

真空阴极离子镀法制备Ti/TiN/Zr/ZrN多层膜

过去,在不锈钢上沉积10μm以上多元多层软硬交替Ti/TiN/Zr/ZrN厚膜用以提高材料耐腐蚀性能的报道不多.采用阴极电弧离子镀结合脉冲偏压的方法制备了厚度选15 μm的Ti/TiN/Zr/ZrN多层膜.运用扫描电镜(SEM)、X射线衍射(XRD)、显微硬度计、划痕仪等考察了多层膜的形貌、厚度、相组成、硬度以及膜/基结合力,并利用电化学方法评价了基体、单层TiN薄膜以及多层膜的电化学腐蚀性能.结果表明:制备的Ti/TiN/Zr/ZrN多层膜界面明晰、结构致密、晶粒细小;膜/基结合力大于70 N,显微硬度达28 GPa;多层膜比单层TiN膜在提高1Cr11Ni2W2MOV基体的抗腐蚀能力方面具有更显著的作用.     

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.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

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.     

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.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.