离子硫氮碳共渗层表层形貌与相结合研究

采用扫描电镜，能谱仪，Ｘ射线衍射仪等分析研究了离子硫氮碳共渗层表面与次表面形貌特征与相结构，探讨了其形成机制。结果表明：硫氮碳共渗表层为以硫化物颗粒组成的多层层状结构，其成分及层数随共渗气氛硫势的变化而豪华；次表层为致密的氮碳化物层和氮，碳扩散层。     

时间和电压对TC4合金表面等离子碳氮共渗层的影响

应用液相等离子电解碳氮共渗技术，在NI-GN03、乙醇和甘油组成的电解液体系下，短时间内在TC4合金表面制备高硬度渗层。探索了时间和电压对膜层的硬度、厚度、相组织和微观形貌的影响。结果表明：随着时间的延长和工作电压的提高，渗层的硬度、厚度均有明显的提高，表面粗糙度变大。并得出了TC4合金进行等离子碳氮共渗的理想电压应控制在280V左右。     

低温活性屏等离子氮碳共渗对3Cr13不锈钢组织和耐蚀性的影响

利用XRD、OM和SEM等试验方法,研究了氮碳共渗温度对3Cr13不锈钢渗层的组织结构及耐腐蚀性的影响。结果表明:当氮碳共渗温度为450℃时,渗层主要由α'N相、少量ε相和γ'相组成;处理温度高于480℃时,渗层中开始有Cr N相析出。氮碳共渗处理样品表面的显微硬度较未处理样品明显升高,且随处理温度升高,显微硬度逐渐增大;试样表面耐腐蚀性在处理温度为450℃时显著提高,随处理温度升高耐腐蚀性降低。     

离子硫氮磷共渗层表层形貌与相结构研究

采用扫描电镜、能谱仪、Ｘ射线衍射仪等分析研究了离子硫氮碳共渗层表面与次表面形貌特征与相结构，探讨了其形成机制．结果表明：硫氮碳共渗表层为以硫化物颗粒组成的多层层状结构，其成分及层数随共渗气氛硫势的变化而变化；次表层为致密的氮碳化物层和氮、碳扩散层，这种渗层结构是其具有良好减摩性、跑合性与耐磨性的原因．     

QPQ处理氮碳共渗温度对45钢组织与性能的影响

对用于制作高压开关构件的45钢进行了3 h盐浴氮碳共渗,抛光后再进行400℃×30 min氧化的QPQ处理。通过观察渗层表面形貌,测量渗层表面硬度及耐磨性,分析了渗层性能与QPQ工艺之间关系。研究结果表明,45号钢在不同QPQ氮碳共渗温度下得到了不同厚度的化合物层,具有很高的硬度和耐磨性。当620℃氮碳共渗时,氮碳共渗层的综合性能最佳。     

氮碳共渗对4Cr10Si2Mo钢渗层组织和表面粗糙度的影响

对4Cr10Si2Mo钢试样进行快速氮碳共渗,在560 ℃保温30 min渗层可达15μm.电子探针成分分析结果表明,氮浓度分布较为均匀,碳浓度在接近表面处最高,随后在渗层中迅速降低,而Cr、Si、Mo在距渗层的表面一定距离处产生聚集.样品共渗层的表面粗糙度受温度和时间两方面的影响,共渗温度提高到570℃或共渗时间超过35 min,样品表面粗糙度变差.     

渗硫参数对氮碳共渗表面形成FeS固体润滑层的影响

采用低温离子渗硫技术在CrMoCu合金铸铁离子氮碳共渗表面制备FeS固体润滑层。通过对FeS固体润滑层表面微观形貌的观察，初步分析了渗硫条件和氮碳共渗表面对其上FeS固体润滑层形成的影响。氮碳共渗表面细小的缺陷和凹坑为硫化物提供了形核的活性中心，利于形成以FeS相为主的较厚的FeS固体润滑层。渗硫温度对氮碳共渗表面形成FeS固体润滑层影响很大，当渗硫温度（硫罐温度／工件温度）为210℃／230℃时，FeS固体润滑层中S／Fe原子摩尔百分比值趋于1；当渗硫温度（硫罐温度／工件温度）小于或大于210℃／230℃时，FeS固体润滑层中S／Fe原子摩尔百分比值远小于1或远大于1，不利于FeS固体润滑层的形成。     

马氏体轴承钢碳氮共渗滚动接触疲劳失效机理EI北大核心CSCD

碳氮共渗工艺应用广泛,但对碳氮共渗后零部件的滚动接触疲劳失效机理研究较少。采用气体碳氮共渗对马氏体轴承钢进行表面改性处理,对碳氮共渗试样进行滚动接触疲劳试验,研究碳氮共渗对轴承钢滚动接触疲劳性能的影响及其失效机理。研究结果表明:碳氮共渗试样表面硬度、残余应力和残余奥氏体含量显著提高,使得其接触疲劳寿命明显高于常规试样。疲劳裂纹萌生于表面和亚表面,其中大量表面平行裂纹主要由表面白色蚀刻层硬度梯度变化而导致,表面材料受到严重微观塑性变形产生晶粒细化;亚表面裂纹萌生位置受最大应力的分布和渗层厚度的影响。表面和亚表面疲劳裂纹的扩展和连接最终导致碳氮共渗试样出现浅层剥落和分层剥落的失效形貌。     

离子硬化工艺在316L不锈钢阀内件中的应用

对316L奥氏体不锈钢进行离子渗氮(PN)和离子碳氮共渗(PNC)处理,利用光学显微镜、显微硬度计、电化学工作站、粗糙度检测仪和三坐标测量仪对试样渗层厚度、显微硬度、耐腐蚀性、表面粗糙度和变形量进行讨论分析。结果表明:316L钢经离子碳氮共渗处理后的渗层硬度分布较好,可提高耐腐蚀性能。离子碳氮共渗技术可应用于阀内件(包括球芯和阀座)的表面硬化处理,在保证零件尺寸配合公差的条件下,大幅提高阀内件的表面硬度。     

38CrMoAl钢轴向柱塞C.N.S.三元共渗后的组织和性能

用金相显微镜和扫描电镜观察和分析了38CrMoAl钢轴向柱塞经气体氮碳共渗和液体碳氮硫共渗后的组织形貌，并且用能谱分析的方法定性地测定了渗层的化学成分。结果表明，三元共渗所用的盐浴成分具有脱氧作用，38CrMoAl钢盐浴碳氮硫共渗的渗层深度为0．38mm、表面硬度为840HV0．2，符合技术要求。     

Effect of plastic side flow on surface roughness in micro-turning process

Kinematic roughness-based surface finish prediction is known to often under-predict the measured surface roughness in turning process, especially at small (micron level) feed rates. It has also been observed that the surface roughness in micro-turning decreases with feed, reaches a minimum, and then increases with further reduction in feed. This paper presents a model for predicting the surface roughness in micro-turning of Al5083-H116 alloy that takes into account the effects of plastic side flow, tool geometry, and process parameters. The model combines these effects with more accurate estimation of the average flow stress of Al5083-H116 at micron scale of deformation with the help of a previously reported strain gradient-based finite element model. The surface roughness model is evaluated through a series of micro-turning experiments. The results show that the model can predict the surface roughness in micro-turning quite well. It is shown that the commonly observed discrepancy between the theoretical and measured surface roughness in micro-turning is mainly due to surface roughening caused by plastic side flow. Further, it is shown that the increase in roughness at low feed can be attributed to the increased side flow caused by strain gradient-induced strengthening of the material directly ahead of the tool.     

改进的单向磨料流加工效果及轴向力测量研究

由合金材料制成的结构复杂工件内通道及相交部位的毛刺难以有效去除,而采用磨料流(AFM)加工工艺可以有效抛光零件复杂表面、提高工件加工质量。基于此,对不同工作压力的单向磨料流作用下,工件的表面粗糙度和扩展直径进行研究,介绍一种适用于单向AFM轴向力在线测量的装置,分析了不同加工压力和流体通道长度对轴向力和体积流量的影响。研究结果表明:4.0 MPa加工压力下的AFM加工可以有效降低工件表面粗糙度,同时使工件获得更均匀的表面粗糙度,但是4.0 MPa条件下的加工时长远大于7.0 MPa;流体通道长度越短,体积流量相对于轴向力来说随着加工压力的增加而明显增加;而对于最长的流体通道,加工压力的增加导致轴向力的增加更为显著。     

有机氟硅烷对玻璃表面的浸润改性

为研究有机氟硅烷对玻璃表面润湿性的影响,利用1H,1H,2H,2H-全氟癸基三乙氧基硅烷对普通玻璃表面进行化学修饰,在玻璃基体表面形成含有-CF3的强疏水性基团。通过控制试验温度和处理时间,研究了不同处理条件下玻璃表面的疏水效果的变化趋势。通过对玻璃表面进行不同程度的打磨处理,研究了玻璃表面粗糙度对表面接触角的影响。利用扫描电子显微镜(SEM)、表面粗糙度测试仪和红外光谱(FTIR)对玻璃表面处理后形貌、粗糙度和化学结构进行了观察和表征,利用表面接触角仪测定了不同处理条件后玻璃表面的接触角。结果表明,浸润时间与温度的增加在一定范围内均可提高玻璃表面疏水性,且表面粗糙度的增加有利于疏水性能的提高。最终通过将表面粗糙化与表面化学修饰相结合,使玻璃表面获得优异疏水性能,表面接触角最高可达到127.9°。     

Simulation for the prediction of surface roughness in magnetic abrasive flow finishing (MAFF)

The final machining (or finishing) of precision parts with high level of surface finish and close tolerance is making the application of magnetic abrasive finishing technology increasingly important. Magnetic abrasive flow finishing (MAFF) is a new abrasive finishing process combining the features of abrasive flow finishing (AFF) and magnetic abrasive finishing (MAF). MAFF provides a high level of surface finish and close tolerances for wide range of industrial application. This paper focuses on the modeling and simulation for the prediction of surface roughness on the workpiece surface finished by MAFF process. A finite element model is developed to find the magnetic potential distribution in the magnetic abrasive brush formed during finishing action and then it is used to evaluate machining pressure, surface finish and material removal. The simulation results are compared with the experimental results available in the literature. The simulated workpiece surface roughness shows features similar in nature to the experimental results.     

Investigation of the effects of electrode orientation and fluid flow rate in near-dry EDM milling

This research investigates the effects of electrode lead and tilt angles and dielectric fluid flow rate on material removal rate, tool electrode wear ratio, and surface roughness in near-dry electrical discharge machining (EDM) milling process. Computational fluid dynamics (CFD) model is developed to predict the dielectric fluid flow rate and qualitatively compare with the experimentally measured EDM material removal rate. The optimum lead angle, which maximized material removal rate and minimized tool electrode wear ratio, was found. The decrease in the lead angle has a negative effect on the roughness of machined surface. The increase in tilt angle reduces the material removal rate and increases the tool electrode wear ratio. The change in tilt angle does not have a significant effect on the surface roughness and can be used to prevent gouging in finishing EDM milling. This study shows that the material removal rate is linearly proportional to the mass flow rate of air and kerosene mixture, the tool electrode wear ratio is inversely related to the mass flow rate of air and kerosene mixture, and the average surface roughness does not have a good correlation with the flow rate of the mixture.     

中厚板氧化铁皮对冷却过程的影响

热轧钢板在轧制时除鳞方式不同,即使采用相同的控冷工艺参数,其终冷温度差异较大,这是由于钢板表面氧化铁皮的厚度和形态不同导致的。为此,研究了氧化铁皮对钢板冷却过程的影响。结果表明:较厚的氧化铁皮使钢板表面粗糙增大,使传热过程中的流动边界层发生变化并对冷却过程中核态沸腾汽泡的产生具有较大影响,从而提高了冷却强度且使钢板冷却不均,出现浪形。同时分析得出:钢板表面麻点缺陷、氧化铁皮破碎、FeO的结构易使其表面粗糙度增大。因此,通过调整加热及热轧过程工艺参数,减少氧化铁皮的形成或避免产生粗糙表面都可以有效避免对钢板造成不均匀冷却,使板形得到明显改善。     

A study on surface roughness in abrasive waterjet machining process using artificial neural networks and regression analysis method

In the present study, artificial neural network (ANN) and regression model were developed to predict surface roughness in abrasive waterjet machining (AWJ) process. In the development of predictive models, machining parameters of traverse speed, waterjet pressure, standoff distance, abrasive grit size and abrasive flow rate were considered as model variables. For this purpose, Taguchi's design of experiments was carried out in order to collect surface roughness values. A feed forward neural network based on back propagation was made up of 13 input neurons, 22 hidden neurons and one output neuron. The 13 sets of data were randomly selected from orthogonal array for training and residuals were used to check the performance. Analysis of variance (ANOVA) and F-test were used to check the validity of regression model and to determine the significant parameter affecting the surface roughness. The statistical analysis showed that the waterjet pressure was an utmost parameter on surface roughness. The microstructures of machined surfaces were also studied by scanning electron microscopy (SEM). The SEM investigations revealed that AWJ machining produced three distinct zones along the cut surface of AA 7075 aluminium alloy and surface striations and waviness were increased significantly with jet pressure.     

阳极氧化处理对钛表面粗糙度和亲水性的影响

本文通过阳极氧化处理技术在钛表面制备出具有不同粗糙度和亲水性的纳米表面。采用扫描电镜观察表面特征,原子力显微镜检测表面粗糙度,接触角仪测量亲水性。实验结果表明,表面形貌随着氧化电压和时间的改变有较大变化。在优化的电解液和氧化条件下,可以在钛表面制备规则排列的纳米管阵列。粗糙度随着氧化时间的延长而增大,在几十到几百纳米之间变化,而氧化电压对粗糙度的影响不大。表面亲水性随着氧化时间的延长先增加,再降低。钛表面结构形貌、粗糙度与亲水性的变化可用阳极氧化过程中表面发生的反应进行解释。     

Influences of chip serration on micro-topography of machined surface in high-speed cutting

Saw-tooth chip changes from macroscopically continuous ribbon to separated segments with the increase of cutting speed. The aim of this study is to find the correlations between chip morphology and machined surface micro-topography at different chip serration stages encountered in high speed cutting. High strength alloy steel AerMet100 was employed in orthogonal cutting experiments to obtain chips at different serration stages and corresponding machined surfaces. The chips and machined surfaces obtained were then examined with optical microscope (OM), scanning electron microscope (SEM), and white light interferometer (WLI). The result shows that chip serration causes micro-waves on machined surface, which increases machined surface roughness. However, wave amplitudes (surface roughness) at different serration stages are different. The principal factor influencing wave amplitude is the thickness of the sawed segment (tooth) of saw-tooth chip. With cutting parameters in this study, surface roughness contributed by chip serration ranges from 0.39 μm to 1.85 μm. This may bring on serious problems in the case of trying to replace grinding with high-speed cutting in rough machining. Some suggestions have been proposed to control the chip serration-caused surface roughness in high-speed cutting based on the results of the current study.     

表面微结构对冰粘附强度的影响

目的研究试片表面粗糙度及分形维数对冰粘附强度的影响。方法通过对裸铝表面进行化学刻蚀及氟硅烷修饰,制备不同表面试片,测试试片表面的粗糙度和分形维数,应用冰粘附强度实验装置测试不同试片表面的冰粘附强度。结果粗糙度(x)与粘附强度(y)的关联式为:y=1.0966x+51.816(亲水表面),y=-0.67x+74.98(疏水表面)。分形维数(z)与粘附强度(y)的关联式为:y=-146.6z+493.5(亲水表面),y=95.45z-209.9(疏水表面)。结论亲水表面试片冰粘附强度随粗糙度的增加而增加,随分形维数的增加而减小,疏水表面试片的变化趋势则相反。冰粘附强度与粗糙度及分形维数之间存在较强的线性关系。表面粗糙度相同的试片经氟硅烷修饰后,冰粘附强度降低,且表面粗糙度越大,冰粘附强度下降越多。