热等静压氮化硅HIP-Si3N4试件断裂韧性测试方法

热等静压氮化硅(Hot Isostatic Pressured silicon nitided ceramics)，一种新型工程陶瓷，作为耐高温、抗腐蚀复合材料，这里简述了陶瓷材料的断裂理论及韧性测试的意义。介绍了直接压痕法、弯曲压痕强度法等几种韧性测试方法。     

热等静压氮化硅陶瓷、钴铬15及钼50钢摩擦学研究

介绍了国内外陶瓷材料研究现状及发展趋势。作为耐高温、耐腐蚀等复合摩擦副材料，介绍了热等静压烧结的氮化硅陶瓷、钴铬15及钼50高速合金钢的摩擦学性能。对陶瓷材料的润滑及摩擦化学反应对陶瓷材料摩擦学特性的影响进行了初步探讨。     

热等静压技术

热等静压工艺是将制品放置到密闭的容器中，向制品施加各向同等的压力，同时施以高温，在高温高压的作用下，制品得以烧结和致密化。已成为当今许多高性能材料生产中一项实用技术，也是新材料开发不可缺少的一种新技术。     

Si3 N4浸渍处理提高硬度的研究

用硅粉冷等静压成型和反应烧结氮化工艺制造的氮化硅样品不规则气孔且多大，硬度偏低。浸渍处理可以填充气孔，显著提高硬度和抗弯强度。     

国内外热等静压技术的发展及应用

本文介绍了近年来国内热等静压技术的发展及热等静压技术在粉末成型、制取复合材料、致密化处理和扩散连接等方面的应用情况。     

热等静压制备Ti(C,N)基金属陶瓷功能梯度材料

用热等静压（HIP）技术制备了Ti（C,N）基金属陶瓷功能梯度材料,对热等静压氮化处理前后的组织结构、硬度以及密度变化作了比较分析。结果表明：HIP技术能在金属陶瓷表面形成硬质薄膜,表面硬度提高,并且硬度由表及里逐渐减小,这是由于高温高压氮化处理使材料中的孔洞闭合,微裂纹和缺陷的减少使得材料性能显著提高。     

热等静压技术的发展及其对铸件性能的改善

本文综述了热等静压技术的发展状况及其对铸造铝合金、镁合金、钛合金、耐高温合金、钢和球墨铸铁性能的改善效果。     

Si3N4复合镀层胶辊制造新工艺

在现代社会中,香烟制造业发展迅速,已经成为我国主要利税产业。本产品就是应用于香烟生产线上的一个重要部件,主要用于对烟纸进行上胶处理。目前,生产线上所使用的胶辊容易磨损,造成精度降低。在无法保证正常使用时,就需要对胶辊     

几种常用添加剂对HIP-Si3N4/GCr15摩擦学性能影响的研究

采用MPX-2000型摩擦试验机，在六种常用添加剂的锂基脂润滑下，对HIP-Si3N4/GCr15（热等静压工程陶瓷/GCr15轴承钢）组成的摩擦副进行了定量试验研究，探讨了二硫化钼与膦之星两种添加剂的作用机理。     

浅析热等静压技术的发展及其设备应用

随着热等静压技术在国防民生领域的运用,热等静压技术开始进入人们的视野,促进生产工艺的提高,方便着人们的生活。     

Microstructure and abrasive wear in silicon nitride ceramics

It is well known that abrasive wear resistance is not strictly a materials property, but also depends upon the specific conditions of the wear environment. Nonetheless, characteristics of the ceramic microstructure do influence its hardness and fracture toughness and must, therefore, play an active role in determining how a ceramic will respond to the specific stress states imposed upon it by the wear environment. In this study, the ways in which composition and microstructure influence the abrasive wear behavior of six commercially-produced silicon nitride based ceramics are examined. Results indicate that microstructural parameters, such as matrix grain size and orientation, porosity, and grain boundary microstructure, and thermal expansion mismatch stresses created as the result of second phase formation, influence the wear rate through their effect on wear sheet formation and subsurface fracture. It is also noted that the potential impact of these variables on the wear rate may not be reflected in conventional fracture toughness measurements.     

Parametric analysis on electrochemical discharge machining of silicon nitride ceramics

The electrochemical discharge machining (ECDM) process has a potential in the machining of silicon nitride ceramics. This paper describes the development of a second order, non-linear mathematical model for establishing the relationship among machining parameters, such as applied voltage, electrolyte concentration and inter-electrode gap, with the dominant machining process criteria, namely material removal rate (MRR), radial overcut (ROC) and thickness of heat affected zone (HAZ), during an ECDM operation on silicon nitride. The model is developed based on response surface methodology (RSM) using the relevant experimental data, which are obtained during an ECDM micro-drilling operation on silicon nitride ceramics. We also offer an analysis of variance (ANOVA) and a confirmation test to verify the fit and adequacy of the developed mathematical models. From the parametric analyses based on mathematical modelling, it can be recommended that applied voltage has more significant effects on MRR, ROC and HAZ thickness during ECDM micro-drilling operation as compared to other machining parameters such as electrolyte concentration and inter-electrode gap.     

氮化硅陶瓷回转曲面零件化学机械抛光工艺实验研究

在数控坐标磨床上应用化学机械抛光(Chemo-mechanical polishing,CMP)技术,对氮化硅陶瓷回转曲面零件进行超精密加工工艺实验研究.分析了氮化硅陶瓷化学机械抛光原理,并搭建化学机械抛光实验平台.通过实验研究了水基CeO2抛光液浓度、抛光液流量、抛光轮转速等主要工艺参数对氮化硅陶瓷零件抛光的表面质量的影响规律,根据实验结果对抛光工艺参数进行了优选.结果表明:在抛光液浓度为20%,抛光液流量为0.6 L/min,抛光轮转速为6 000 r/min的条件下,能获得较好的抛光表面质量,其表面粗糙度Rα达12 nm.     

Wear mechanisms in oil-lubricated and dry fretting of silicon nitride against bearing steel contacts

The wear and friction behaviour of silicon nitride against bearing steel was investigated under lubricated and dry fretting conditions as a function of amplitude and test duration. Tests were performed on a high frequency fretting tester. Silicon nitride bearing balls were used as the upper oscillating specimens while the lower stationary flats were standard specimens of bearing steel. Amplitudes in the intermediate 5 to 50 μm range and a test duration from 10 to 360 min were studied. In lubricated conditions a commercial lubricant. ISO VG 220, was used. Light microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Auger spectroscopy (AES) and transmission electron microscopy (TEM) were employed to determine the wear mechanisms.

Under lubricated conditions transition from high to low wear volumes was recognised with increasing amplitude. At lower amplitudes and in the early stage of fretting tests at moderate amplitudes, mechanical wear dominated. Cracks on the stick-slip boundary and spalling of a thin tribolayer was observed. Under these conditions the highest wear in lubricated fretting was obtained. In the final stage of fretting tests at moderate amplitudes, and from the beginning at higher amplitude, tribochemical wear is suggested as the dominant wear form. A 0.2 μm thick tribolayer was observed on the contact, containing inclusions with different Fe and Si contents. A very high concentration of carbon, formed by oil degradation, was also determined in this layer, confirming the critical influence of oil on the wear behaviour.

Quite a different wear mechanism is proposed for dry fretting conditions. Results of AES analysis showed a layer an order of magnitude thicker than in lubricated fretting, also having a remarkably different chemical composition. TEM analysis confirmed that the reaction layer consisted of a silica-rich amorphous phase containing small inclusions of Fe₂O₃ and Fe₃O₄. In contrast to lubricated conditions, where the layer created was ductile, in the case of dry fretting the layer was brittle. The continuous process of forming and spalling the brittle tribolayer caused much higher wear rates and wear losses than under lubricated fretting conditions. No transition in wear behaviour was observed as was the case in lubricated fretting.     

Effects of support method and mechanical property of 300 mm silicon wafer on sori measurement

This paper describes the effects of support methods and mechanical properties of 300 mm silicon wafer on sori measurement. A new supporting method, named three-point-support method, used in the sori measurement of a large diameter silicon wafer was proposed in this study to obtain a more stable measuring process. The wafer was supported horizontally by three steel balls on the vertexes of a regular triangle at the wafer edge. The measuring repeatability and anti-disturbance ability were compared between the proposed method and the conventional one-point-support method, in which the wafer is supported with a small-area chuck at the wafer center. The effects of friction between the supports and wafer surface for the three-point-support were also estimated. Finally, the influences of different mechanical characteristics at the front and back surfaces and the crystal orientation on sori measurement were investigated.     

A comparison of the microstructure of silicon nitride-silicon carbide composites made with and without deoxidized starting material

Two different types of silicon carbide (SiC) matrix composites, with either 10 wt% or 20 wt% silicon nitride (Si₃N₄) reinforcement, were fabricated to investigate the effect of pretreatment on the resulting composite micro-structure. The first type of composite was prepared from as-received α-SiC and α-Si₃N₄ powders, while the second type was prepared from powder compacts that had been deoxidized to eliminate surface silica on the powder particles. The composites were hot isostatically pressed in tantalum cans at 2373 K for 1h under a pressure of 200 MPa. Density measurements showed that full theoretical density was achieved for the composites prepared from the as-received powders, while much lower densities were obtained for the composites prepared from the deoxidized green compacts. Almost all of the α-SiC transformed into β-SiC, and almost all the α-Si₃N₄ transformed into α-Si₃N₄ in the composites made from the as-received powders, while in the composites made from the deoxidized material the α-SiC remained untransformed and both α-Si₃N₄ and β-Si₃N₄ phases were present in significant quantities. High-resolution transmission electron microscopy and Fresnel fringe imaging were used to identify the grain boundary and interphase boundary structure. Most interfaces were found to be covered with ? 1 nm thick amorphous intergranular films in the composites prepared from as-received powders, whereas most interfaces were found to be free of such amorphous intergranular films in the composites prepared from the deoxidized material. Taken together, the presence of intergranular films at the interfaces and the results from density measurements are consistent with the densification and reverse α → β-SiC transformation taking place in the composites made from as-received powders by a liquid-phase sintering route. An incomplete liquid-phase sintering mechanism is also able to explain the microstructure observed in the composites made from the deoxidized material.     

Surface strength of silicon nitride in relation to rolling contact performance measured on ball-on-rod and modified four-ball tests

Silicon nitride (Si₃N₄) has been used in various rolling contact applications in turbomachinery, automotive and power industry. It is favoured to replace conventional steel due to its low density, low friction, corrosion resistance and good performance under extreme condition. However, a major limitation of its wider application is its high material and machining cost, especially the cost associated with the finishing process. In the present study, a low cost sintered and reaction bonded silicon nitride (SRBSN) is used to study the surface machining effects on its rolling contact performance. Attempt has been made to link the surface strengths of Si₃N₄ derived from half-rod and C-sphere flexure strength specimens to the rolling contact lifetimes of Si₃N₄ rod and ball specimens. The rolling contact fatigue tests are carried out on ball-on-rod and modified four ball machines. Three types of surfaces with coarse, fine and conventional finishing conditions are examined. Flexure strength tests on half-rod and C-sphere show an increasing surface strength from specimens with coarse, fine to conventionally machined conditions. During rolling contact fatigue test of as-machined specimens, there are no failures observed on both ball-on-rod and four ball tests after 100 million stress cycles. However, there is a trend of decreasing wear volumes measured on the contact path of rods and balls with coarse, fine and conventional conditions. In four ball test, spall failures are observed on pre-crack specimens. There is a trend of increasing rolling contact fatigue lifetime from pre-cracked specimens with coarse, fine to conventional machining conditions.     

发动机热试台架的组成及应用

发动机的热试为发动机制造过程中的一项重要环节,主要对发动机的性能、排放、可靠性及耐久性等方面进行测试。描述了热试台架的组成及其实际应用,从台架构造、测试系统、电气控制系统及公用系统等方面论述了一个高效、环保及低成本的热试系统。通过实际生产应用,说明了该热试系统在小排量发动机测试方面的实用性及经济性等。