放电参数对PCD表层材料微观结构影响的实验研究

通过调整电火花成形加工的主要放电参数,对聚晶金刚石(PCD)样品进行放电加工.进而对样品进行X射线衍射分析,并在扫描电子显微镜下观察其表层结构.弄清了放电加工后PCD表面变质层的主要成分及其产生的原因,分析了脉冲宽度和加工电流对PCD表面变质层深度、表面粗糙度的影响.为制定PCD放电加工工艺提供了重要的实验依据.     

聚晶金刚石电火花磨削试验的人工神经网络建模

聚晶金刚石(PCD)由于具有高硬度、高耐磨性和抗腐蚀性等优良的特性,其应用范围日益广泛,但是其成型加工非常困难。目前,聚晶金刚石常用的加工方法有机械研磨和电火花磨削,由于机械研磨效率低、金刚石层厚度不均匀等缺点,其应用受到很大限制。而电火花磨削工艺加工效率高,PCD平面度易于控制,近年来得到了迅速的发展。电火花磨削工艺主要参数如工件极性、脉冲宽度、脉冲间隔、峰值电压和峰值电流对工艺指标金刚石材料去除率(MRR)均有影响,而一般的方法难以确定工艺参数与工艺指标的关系,本文建立了电火花磨削参数和金刚石材料去除率的人工神经网络模型,该模型对未知工艺条件下的预测结果最大误差为14．29％,基本满足工程实际的需要。     

聚晶金刚石电火花磨削试验的灰色关联分析

聚晶金刚石(PCD)具有高硬度、高耐磨性和抗腐蚀性等优良的特性，但是其成型加工非常困难。目前，聚晶金刚石常用的加工方法有机械研磨和电火花磨削，由于机械研磨效率低、金刚石层厚度不均匀等缺点，其应用受到很大限制。本文采用BDDG-Ⅲ型聚晶金刚石电火花磨削专用机床对其加工规律进行了研究，并采用灰色关联分析理论阐述了聚晶金刚石电火花磨削试验的分析方法，对电火花磨削主要参数脉冲电源输出峰值电压、间隙电压和电容值对表面质量的影响程度进行了研究，给出了其算法并编制了相关的程序。结果表明，在影响聚晶金刚石加工表面质量的三个主要参数中，脉冲电源输出峰值电压为优势因素，其次为电容，间隙电压为次要因素。     

等离子堆焊Q235电解打壳锤头的组织和性能

采用等离子堆焊技术在Q235铝电解打壳锤头表面堆焊F40合金粉末熔覆层。利用扫描电镜、能谱仪和显微硬度计等分析等离子堆焊层的微观组织、微区成分和硬度分布。利用磨擦磨损仪对试样进行耐磨性测试,通过恒电位法评估堆焊层和基体的耐蚀性能。结果表明,堆焊层与基体形成了良好的冶金结合,堆焊层为典型的柱状晶组织。等离子堆焊层平均显微硬度为444HV0.1,为基体的2倍;耐磨性为基体的1.6倍;腐蚀速率Rcorr为3.524×10-4 mm/a,为基体的1/(4.2×104)。等离子堆焊后Q235钢材料的耐磨性、硬度和耐腐蚀性均有显著提高,有望提高电解铝打壳锤头的耐磨耐蚀性能。     

超声振动辅助电火花脉冲放电表面强化层性能研究

采用超声振动辅助电火花脉冲放电表面强化技术进行了65 Mn钢硅电极表面强化.研究了超声振动振幅和频率对表面强化层的厚度分布、显微硬度、表面粗糙度、耐磨性和耐腐蚀性的影响.研究表明,超声振动辅助电火花脉冲放电表面强化技术可改善表面强化层的厚度分布,提高强化层的显微硬度、表面粗糙度、耐磨性和耐腐蚀性.     

工作液对线电极电火花磨削陶瓷表面性能的影响

利用扫描电镜观察、比较碳化硼陶瓷加工表面弹性性能及加工表面变质层.采用不同工作液用线电极电火花放电磨削方法加工工件,得出采用添加铝粉的工作液加工所得工件表面力学性能较好.     

激光熔覆和电火花沉积复合涂层的组织和性能研究

研究了激光熔覆和电火花沉积处理后Q 235钢表面复合涂层的组成、硬度和耐磨性。结果表明:电火花沉积层中弥散分布着细小的硬质相颗粒,提高了涂层的显微硬度和耐磨性。复合涂层的耐磨性是Q 235钢基体的2.3倍。     

磨削深度对42CrMo钢磨削强化层的影响

研究了磨削深度对42CrMo钢强化层组织与硬度的影响。结果表明,在不同磨削深度条件下,强化层的马氏体粗细不均,表层显微硬度随磨削深度先增加后降低,完全强化层显微硬度在720～800 HV0.1之间,比基体硬度提高了2倍。随着磨削深度的增加,强化层厚度最小值也增加,在磨削深度为0.6 mm时强化层厚度可达1.8 mm。     

氧-乙炔热喷涂Ni基粉末对Q235钢组织性能的影响

在Q235钢表面采用氧乙炔喷枪热喷涂Ni基粉末,SEM检测发现,Ni粉和基体除了基本的机械结合外还存在少量的冶金结合.经热喷涂后表面显微硬度由基体的110HV提高到接近380 HV,显微硬度提高了至少2倍,沿纵向从改性层表面到基体显微硬度逐渐降低.     

硼铸铁等离子相变强化层的组织与性能

采用等离子束对硼铸铁进行了表面强化,对等离子强化层的显微组织、显微硬度和耐磨性进行了研究。结果表明:硼铸铁经等离子束淬火处理后,其强化层的组织为隐针马氏体+残余奥氏体+片状石墨+硼化物,硬度为未处理的2￣3倍,强化层的显微硬度随深度呈非线性关系,最高硬度达1 000 HV0.1。且随工作电流的增加,强化层的深度增加,表面硬度下降,次表层硬度增大且硬化层的耐磨性大幅度提高。     

聚晶金刚石电火花超声机械复合加工技术研究

聚晶金刚石具有优良的力、热、化学、声、光、电等性能,在现代工业、国防等领域中得到日益广泛的应用。但是,聚晶金刚石硬度高,耐磨性好,其成型加工非常困难,超声电火花机械复合加工技术是一种有效的加工方法。本研究在分析电火花超声机械复合加工原理的基础上,采用青铜结合剂金刚石砂轮实现了聚晶金刚石的超声电火花机械复合加工。实验分析了超声电火花机械复合加工过程工艺参数与加工效果之间的关系,结果表明,脉宽、脉间、峰值电流、超声振幅、开路电压等参数对复合加工过程工艺结果的影响程度较明显。     

Study on PCD machining

Polycrystalline diamond, PCD, is known for its superior characteristics such as hardness, toughness and wear resistance. However, due to these factors, manufacturing PCD tools is a difficult material removal process. Using quantitative analysis, this study compares the machining effect on a PCD V-cutter including EDM and grinding. The conclusions show that grinding is better than EDM for machining PCD, and with proper parameters, the PCD will be less damaged and retain its superiorities as a cutting tool. In addition, this study presents a beginning for research on understandings of principles in cutting PCD. It may be useful for toolmakers to produce a high quality and reusable PCD tools.     

Performance and Surface Integrity of Ti6Al4V After Sinking EDM with Special Graphite Electrodes

Titanium and its alloys have high chemical reactivity with most of the cutting tools. This makes it difficult to work with these alloys using conventional machining processes. Electrical discharge machining (EDM) emerges as an alternative technique to machining these materials. In this work, it is investigated the performance of three special grades of graphite as electrodes when ED-Machining Ti6Al4V samples under three different regimes. The main influences of electrical parameters are discussed for the samples material removal rate, volumetric relative wear and surface roughness. The samples surfaces were evaluated using SEM images, microhardness measurements, and x-ray diffraction. It was found that the best results for samples material removal rate, surface roughness, and volumetric relative wear were obtained for the graphite electrode with 10-μm particle size and negative polarity. For all samples machined by EDM and characterized by x-ray (XRD), it was identified the presence of titanium carbides. For the finish EDM regimes, the recast layer presents an increased amount of titanium carbides compared to semi-finish and rough regimes.     

The effect in EDM of a dielectric of a urea solution in water on modifying the surface of titanium

This study investigates the influence of the machining characteristics on pure titanium metals using an electrical discharge machining (EDM) with the addition of urea into distilled water. Additionally, the effects of urea addition on surface modification are also discussed. In the experiments, machining parameters such as the dielectric type, peak current and pulse duration were changed to explore their effects on machining performance, including the material removal rate, electrode wear rate and surface roughness. Moreover, the elemental distribution of nitrogen on the machined surface was qualitatively determined by EPMA to assess the effects on surface modification. Micro hardness and wear resistance tests were performed to evaluate the effects of the reinforced surface.Experimental results indicate that the nitrogen element decomposed from the dielectric that contained urea, migrated to the work piece, forming a TiN hard layer, resulting in good wear resistance of the machined surface after EDM.     

Surface modifications of Al–Zn–Mg alloy using combined EDM with ultrasonic machining and addition of TiC particles into the dielectric

This study proposes a novel combined process that integrates electrical discharge machining (EDM) and ultrasonic machining (USM) to investigate the machining performance and surface modification on Al–Zn–Mg alloy. In the experiment, TiC particles were added into the dielectric to explore the influence of the combined process on the material removal rate (MRR), the relative electrode wear ratio (REWR), the surface roughness and the expansion of the machined hole. The elemental distributions of titanium and carbon on the cross-section were quantitatively determined using an electron probe micro-analyzer (EPMA). Microhardness and wear resistance tests were conducted to evaluate the modifications on the machined surface caused by the combined process. The experimental results show that the combined process was associated with improved machining performance. The combination of EDM with USM yielded an alloyed layer that improved the hardness and wear resistance of the machined surface.     

Surface modification of Al–Zn–Mg alloy by combined electrical discharge machining with ball burnish machining

The study investigated the feasibility of modifying the surface of Al–Zn–Mg alloy by a combined process of electric discharge machining (EDM) with ball burnish machining (BBM). A novel process that integrates EDM and BBM is also developed to conduct experiments on an electric discharge machine. Machining parameters of the combined process, including machining polarity, peak current, power supply voltage, and the protruding of ZrO₂, are chosen to determine their effects on material removal rate, surface roughness and the improvement ratio of surface roughness. In addition, the extent to which the combined process affects surface modification is also evaluated by microhardness and corrosion resistance tests. Experimental results indicate that the combined process of EDM with BBM can effectively improve the surface roughness to obtain a fine-finishing and flat surface. The micropores and cracks caused from EDM are eliminated during the process as well. Furthermore, such a process can reinforce and increase the corrosion resistance of the machined surface after machining.     

GT35钢结硬质合金电火花加工工艺试验

研究了GT35电火花加工时,峰值电流、脉冲宽度、放电时间等参数对工件加工效率、加工面粗糙度和电极耗损速度等的影响规律,并分析了其作用机理,优化了GT35钢结硬质合金电火花加工工艺参数,为加工复杂型腔GT35钢结硬质合金模具提供了试验依据。     

大面积PCD复合片电火花加工高效节能脉冲电源的研究

本文通过对大面积PCD复合片材料物理特性的分析及电火花放电加工PCD表面放电机理的研究，分析了电火花加工大面积PCD复合片时影响加工速度及表面质量的重要因素。提出了用于加工大面积PCD复合片的理想电源模型，其特点为：大能量、高峰值电压、高峰值电流、窄脉冲、等脉冲能量输出。根据理想电源模型开发出一种高效、节能、环保型大面积PCD复合片电火花专用脉冲电源。与普通电火花脉冲电源比较，该电源加工效率高、加工表面质量好，电能利用率高，是大面积PCD复合片电火花加工的有效工具。     

PCD、PCBN复合片的电火花线切割加工质量

选取几种典型的PCD、PCBN复合片,在慢走丝电火花线切割机床上对其进行了多次加工工艺试验;运用三维表面轮廓仪、超景深三维显微镜对线切割加工后的表面粗糙度、富钴界面层加工质量、刃口加工质量等进行测量。结果表明:超硬颗粒直径大小及含量对加工质量影响较大,PCD、PCBN复合片经多次电火花线切割加工,能够得到较好的加工质量;经WEDM加工后的PCD复合片刃磨量可控制在4～15μm左右,PCBN复合片BNX20刃磨量可控制在10μm以内,而BZN6000则需较大的刃磨量。     

陶瓷金刚石砂轮在YG10X顶锤磨削加工中的应用

采用自行设计的陶瓷结合剂金刚石砂轮加工硬质合金顶锤,用低浓度金刚石砂轮加工其平面,用高浓度金刚石砂轮加工其外圆,并与树脂金刚石砂轮的磨削加工进行对比。实验结果表明:同等条件下陶瓷金刚石砂轮的锋利度要高于树脂金刚石砂轮的锋利度,其加工速度更快,且磨削产生的热要远低于树脂砂轮的;平面磨削中,陶瓷金刚石砂轮通过调整工艺参数或调细金刚石粒度能够获得更好的表面粗糙度;外圆磨削中,陶瓷砂轮较树脂砂轮加工效率提升约50%,当陶瓷金刚石砂轮浓度达到200%时,砂轮性价比最高。