铝微粉对大气环境感应钎涂金刚石涂层性能影响

金刚石钎涂是材料表面修形提性的重要技术手段,由于金刚石的超硬特性使得钎涂涂层中金刚石与钎料的性能难以匹配. 在镍基钎料中加入铝微粉,研究Al对涂层组织及耐磨性的影响. 结果表明,Al的添加降低了金刚石钎涂层孔隙率,同时钎涂过程中在基体内原位生成Al₂O₃相,提高了金刚石钎涂层的耐磨性. 阐明了Al脱氧消减气孔及其脱氧产物Al₂O₃作为原位生成硬质相增强涂层硬度及耐磨性的机制.进一步揭示了原位生成Al₂O₃可细化、强化钎料组织,优化涂层形态、增加涂层厚度的机理.明确了感应钎涂中活性微粉的脱氧作用和原位生成氧化物陶瓷的耐磨作用.     

感应加热金刚石/镍基复合涂层微观组织与性能

采用感应加热的方式,在65Mn钢基体表面制备了金刚石质量分数为10%的复合镍基涂层,利用SEM、EPMA、XRD对钎涂接头的微观组织和相组成进行了分析,研究了感应钎涂中金刚石/钎料界面的元素扩散机制和形成机制。并利用干砂橡胶轮磨损试验机测试了涂层的耐磨性能,分析了金刚石/镍基涂层的耐磨增强机制。结果表明,钎涂层中钎料合金物相主要为Ni₄B₃、(Ni,Fe)固溶体、Ni₃Si₂、CrB;金刚石与钎料合金发生了冶金反应,金刚石/钎料合金界面的C元素分布促使金刚石表面出现了双层碳化物结构,分别为金刚石侧的Cr₃C₂和在Cr₃C₂表面生长的Cr₇C₃。金刚石复合涂层的耐磨性能显著优于钢基体,涂层60min磨损失重仅0.25g,为钢对比试样磨损失重的1/12,金刚石在磨损过程中起到了阻挡犁沟扩展的作用,涂层的失效机制为镍基合金磨损和金刚石的脱落。     

感应钎涂金刚石/镍基合金复合涂层的性能

以45钢为基体,采用感应钎涂工艺在其表面制备金刚石/镍基合金复合涂层,通过洛氏硬度计、磨粒磨损试验机对涂层进行硬度和耐磨性测试,采用超景深显微镜、扫描电子显微镜对涂层、钎料和金刚石形貌进行观察,采用EDS对金刚石表面微区进行成分分析,初步研究了复合涂层的微观形貌、磨损规律及机制. 结果表明,金刚石颗粒在镍基合金复合涂层中弥散分布,与钎料合金实现了良好的冶金结合. 随着金刚石含量增加,可显著提高复合涂层的硬度及耐磨性. 当金刚石质量分数为20%时,涂层的宏观硬度达到63 HRC,较纯钎料涂层提高1.5倍;在相同的磨损试验条件下,纯钎料涂层的磨损失重为0.335 4 g,金刚石含量为20%的复合涂层磨损失重为0.097 9 g,仅为纯钎料涂层的29.2%.     

Effects of environmental atmospheres on tribological behaviors of sintered polycrystalline diamond sliding against silicon nitride

To explore the effect of various atmosphere the tribological behaviors of the sintered polycrystalline diamond compacts (PDCs), the friction and wear behaviors of PDCs sliding against Si₃N₄ balls were evaluated by a ball-on-disk tribometer under nitrogen, argon, oxygen and air (10% relative humidity) environments, respectively. The energy dispersive X-ray spectrum (EDS), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscope (AFM) were conducted to investigate the microstructure evolution of worn surface. The results demonstrated that the low friction appeared in argon and nitrogen environment. The formations of consecutive carbonaceous transfer films on wear scars contributed to decrease the friction during sliding process. The wear of PDCs and Si₃N₄ balls were serious in argon and nitrogen environment, but slight in oxygen and air conditions. There is a direct relationship between material removal and running-in period. The passivation effect of dangling bond under oxygen and air conditions can shorten the running in period thus weaken the wear.     

Analysis of tool wear and residual stress of CVD diamond coated cemented carbide tools in the machining of aluminium silicon alloys

Aluminium alloys have found increasing applications in the automotive and aeronautical industries in recent years. Due to their extraordinary properties however, the machining of these alloys still poses difficulties, and requires the optimized combination of cutting tool material and geometry. The potential of CVD diamond coated carbide tools has been demonstrated in recent years, however tool wear and short tool life remain as issues to be resolved. Key to increasing the tool life of CVD diamond coated tools is the further development of the coating process to optimize the coating adhesion. An understanding of the substrate and coating residual stress profiles must be gained in order to achieve this. Compressive residual stresses in cutting tools can lead to a higher crack resistance, but also to early coating delamination and tool failure. To analyze the influence of residual stresses on the coating quality and tool life, the residual stress profiles of tungsten carbide substrates and CVD diamond coatings were measured using X-ray and synchrotron radiation. The influence of the tungsten carbide substrate type and the CVD diamond coating process on the residual stress profiles was thus determined. In order to analyze the performance of the coated tools and the influence of the residual stresses on the tool lifetime, machining tests were performed with two aluminium silicon alloys. The tool wear, tool lifetime and workpiece quality were examined. Finally, many of the commonly used wear tests used to analyze the wear resistance of tool coatings cannot be implemented for CVD diamond coatings due to their high hardness. An impact test was therefore constructed to allow the determination of the wear resistance of CVD diamond tools.     

Co含量对金刚石–WC–Co复合材料耐磨性的影响

随着采矿和城市基建等行业的发展,对矿用WC–Co采掘工具的耐磨性提出了更高的要求。通过添加金刚石增强WC–Co矿用工具的耐磨性是一种可行的新思路。在烧结制备金刚石–WC–Co复合材料的过程中钴相作为催化剂会加速金刚石向石墨转变。为研究Co对复合材料中金刚石石墨化程度的影响,采用放电等离子体烧结技术(SPS)制备金刚石–WC–Co复合材料,分析了复合材料中金刚石石墨化程度并采用砂轮法研究了复合材料的磨损性能和磨损机理。结果表明：金刚石–WC–Co复合材料中金刚石可以起到增韧效果;Co含量增加会促进复合材料致密化进程,同时也会降低复合材料的硬度;随着Co含量增加,复合材料材料耐磨性变差。磨损过程中 WC–Co基体率先被磨损去除,金刚石后被磨损,金刚石会增强材料的耐磨性能。     

Wear characteristics of Fe-based diamond composites with cerium oxide (CeO2) reinforcements

To obtain better wear resistance for the metal bond diamond grinding tools, cerium oxide (CeO₂) with different contents were introduced into Fe-based diamond composites. A pin-on-disc wear test was performed to assess the wear properties of the fabricated specimens, and the morphological properties of the worn surface and corresponding wear debris were evaluated to examine the wear mechanism. Results show that the Fe-based diamond composites with CeO₂ addition exhibited an improvement in the densification, mechanical properties and wear resistance. The original long rod-shaped CeO₂ particles converted into the spherical particles <1 μm, dispersing in the Sn phase. The cerium oxide acted as a sintering aid, promoting the diffusion of Fe in the Sn phase during the sintering process. The dominant wear mechanism of the specimen with CeO₂ addition was the adhesive wear, compared with the abrasive wear in the specimen without CeO₂. With the increase in CeO₂ addition amount, the wear rate decreased. But an excessive amount of CeO₂ was detrimental to mechanical and wear performances. The optimal amount of cerium oxide to achieve the best wear resistance was investigated to be 0.8 wt%.     

Determination of wear parameters and mechanisms of diamond/copper tools in marble stones cutting

In this paper, a type of soft metal binder of diamond tools (diamond segments) that was consisted of 78% Brass (Cu-10Zn) +16% Bronze (Cu–10Sn) + %6Co was investigated. The first, it was approved that the binder is a soft metal binder by a hardness test for diamond tools in natural stones cutting. Then, the effective factors on grinding efficiency such as specific energy (SE), Cutting force (FC), metal binder removal rate (MRR), grinding ratio (G-ratio), wear resistance and Mean free path (MFP) were evaluated by different formula and equations. On the other hand, the effect of different wear mechanisms on the metal binder and diamond grits of the tool was evaluated by the cutting of a type of very hard marble stone that calls Cappochino Beige Marble (CBM). The existence of wears of abrasive, surface fatigue, impact and erosive were confirmed by scanning electron microscopic observations. According to hardness 73 HRB (hardness of the binder) and the wears, there is a short tools life for the diamond tool due to low wear resistance of the metal binder but, the cutting rate was high.Novelty statementThe rising price of decorative stones will increase the final price of the stones and will overshadow the global market of decorative stones. The presence of cobalt, iron, chromium and nickel powders increases the price of diamond tools because of their high price. On the other hand, due to the higher temperature and time of hot press to produce these tools by the mentioned powders, it will also increase the price. Therefore, in this paper, brass and bronze alloy powders, which are much cheaper than cobalt, iron, chromium and nickel powders, have been used as main metal binder powders to reduce raw material prices and manufacturing process costs. On the other side, due to the creation of a softer metal binder compared with the more expensive and harder binder of cobalt, iron, chromium and nickel powders, it can be affected to increase the cutting speed because of increasing wear of the binder. Therefore, mathematical calculations are essential for the efficiency of the tools' cutting.     

Cu-Fe基金刚石锯片刀头真空液相烧结性能研究

采用真空液相烧结的方法,设计了Cu-n基刀头基体配方,以低熔点铜基预合金粉末为粘结相,并添加Ti、Cr等活性金属粉末改善基体与金刚石的结合力,通过组织观察及性能分析,讨论了粘结相．骨架相及活性金属含量对基体及刀头性能的影响。随Ti含量的增加,粘结相对骨架相的润湿能力增强,基体的硬度增加,基体对金刚石的结合力提高,刀头的耐磨性增加。随粘结相含量的增加,基体的合金化及致密性提高、硬度增加．刀头的耐磨性增加;硬质颗粒含量较少时对基体的增强作用是弥散强化,当硬质颗粒形成连续骨架时形成颗粒增强。     

Wear resistance and thermal stability enhancement of PDC sintered with Ti-coated diamond and cBN

Ti-coated diamond with different particle sizes and proper amounts of cubic boron nitride (cBN) was used to fabricate polycrystalline diamond composite (PDC) with improved wear resistance and thermal stability under high temperature and high pressure (5.5–6.5GPa, 1500–1650 °C). The ratio of Ti-coated diamond powder, cBN powder and normal diamond powder was W_30–50: W_4–8: W_0–1 = 70: 15: 15. Cobalt (Co) was used as a binder, and cemented tungsten carbide was used as a substrate to sinter a new high-performance PDC. Ti and TiC on the surface of Ti-coated diamond reacted with cBN under high temperature and high pressure to generate new ceramic phases such as TiB₂, TiN and TiN_0.3, which have high hardness and good wear resistance. Compared with the conventional PDC, the impact toughness and wear resistance of PDC with Ti-coated diamond and cBN addition were enhanced by 19% and 28%, respectively. The ceramic phase acts as a protective barrier, which enhances the initial graphitization and oxidizing temperature to 942–950 °C, which were 162–170 °C higher than the conventional PDC. The new ceramic barrier wrapped around the surface of the diamond and Co after the formation of the D-D (diamond-diamond) bonding will give priority to the oxidation reaction of Co and diamond with oxygen, which prohibits cobalt-catalytic graphitization of diamond, meeting the needs of PDC thermal stability and wear resistance in the field of drilling.     

The effect of operational parameters on diamond tools of frame sawing system: Wear characteristics and optimization in stone processing

A series of sawing experiments was carried out to investigate the effect of operational parameters on the wear characteristics of diamond segment. And the wear mechanism of diamond segment was studied through micro-morphology. The analysis presented that the wear mechanisms of segment metal matrix are mainly attributed to abrasive wear and erosion wear, the wear mechanism of diamond particles mainly includes cleavage fracture caused by the impact load and abrasion caused by scratching. The effect of sawing parameters on the wear rate of segment matrix is consistent with that of diamond particles. The wear resistance of segment matrix increases with the increase of the proportion of diamond particles with micro-fractured and complete crystalline shape, and decreases with the increase of the proportion of diamond particles with macro-fractured and pulled-out. Furthermore, the predicted model was established to evaluate the segment wear per unit by using Design Expert software, and the optimum sawing parameters obtained as a result of the optimization was investigated to provide some guidance for the processing of the enterprise.     

Effect of vacuum annealing temperature on tribological behaviors of sintered polycrystalline diamond compact

The sintered polycrystalline diamond compacts (PDCs) were annealed at 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, and 800 °C under vacuum environment. The friction and wear behaviors of the annealed PDCs sliding against Si₃N₄ balls were evaluated by a ball-on-disc tribometer in ambient atmosphere. The compositions, microstructures and surface morphologies of PDC discs and wear scars on Si₃N₄ balls were characterized by energy dispersive spectroscopy (EDS), Raman spectroscopy, and scanning electron microscopy (SEM), respectively. The experimental results demonstrated that the steady friction coefficient decreased at the annealing temperature of 200 °C and increased with annealing temperature increasing. While, the wear rate of PDCs and Si₃N₄ balls increased at 200 °C, and sharply decreased from 300 to 800 °C. The surface morphologies and Raman spectra revealed that the variation law of friction coefficient curves at different annealing temperatures was attributed to carbonaceous transfer films formed on Si₃N₄ balls. The residual stress on PDC surface was reduced after the annealing treatment, thus fine diamond grains were easily extracted from PDC surface onto the contact area during the tribotest which led to the wear of PDC and abrasive wear for both counter parts. These results revealed that the friction and wear behaviors of PDC were significantly affected by the vacuum annealing temperature.     

冲击能量对 Fe-C-Mo-V 堆焊合金抗磨粒磨损性能的影响

采用含Fe-C-Mo-V的气体保护药芯焊丝堆焊制备磨损试样,并对其进行不同冲击能量下的动载冲击磨粒磨损试验. 通过扫描电子显微镜配合能谱分析、磨损失重测试和激光扫描共聚焦显微镜观察等测试方法,对熔敷金属的显微组织及磨痕特征进行分析及表征,研究了熔敷金属在不同冲击能量下的磨粒磨损行为. 结果表明,熔敷金属的显微组织主要由奥氏体基体、层片状共晶组织及团块状的VC硬质相构成. 熔敷金属的磨损失重、磨痕粗糙度以及磨痕深度均随冲击能量的增加而逐渐减小. 磨损机制为磨粒对奥氏体基体的微观切削以及塑性变形. 随着冲击能量的增加,熔敷金属产生加工硬化,磨痕亚表面出现形变马氏体组织,且VC硬质相与层片状共晶组织相互作用,共同提高堆焊层的硬度,从而提高基体的耐磨性,增强抗冲击性能.     

纳米金刚石在摩擦副界面的减摩耐磨机理探讨

本文根据纳米金刚石在摩擦学领域的一些应用结果,初步探讨了纳米金刚石在摩擦副界面的减摩耐磨机理,指出了该应用领域有待深入研究的问题。纳米金刚石加入润滑油中,可以在摩擦副界面起到显著的耐磨减摩作用。纳米金刚石颗粒在摩擦副之间的作用包括纳米金刚石对摩擦界面表面抛光,形成一层摩擦系数极低的金刚石固体边界润滑膜以及在黑色金属摩擦副中纳米金刚石表面石墨化等。     

微波诱发热爆法制备钛铝碳结合剂金刚石复合材料

采用Ti、Al、石墨和金刚石粉体为原料,通过微波诱发热爆法制备钛铝碳结合剂/金刚石复合材料,研究金刚石质量分数和颗粒平均尺寸对复合材料物相组成、显微形貌及磨耗比的影响.结果表明:在N2气氛下,原料粉末发生热爆反应,可生成Ti2AlC、Ti3AlC2、TiC、TiN、AlN和Al3Ti相.当采用较低的金刚石质量分数或较大...     

Investigation and improvement of wear nonuniformity of diamond tools in sawing granite

Sawing experiments were accomplished to discuss the wear characteristics at different parts of diamond tools in the process of sawing granite in this paper. Optical microscopy, scanning electron microscopy and 3D laser microscope were main detection means for the morphology of diamond tools. Synthetic investigation on the abrasion performance of segments was developed from aspects of the wear appearance of diamond particle and metal bond, the particle protrusion height and the residual height of segments. The results indicated that smaller residual height and larger proportion of macro-fractured and pull out crystal were exhibited at the front end of traditional diamond segment compared with the rear end. Morphology characteristics of diamond tools demonstrated different abrasion mechanism, flush erosion and cavitation was the main wear mechanism for the front end, while abrasive wear was the main wear mechanism for the rear end. Maximum undeformed chip thickness per diamond particle for the front end was larger than that of the rear end due to the existence of slot, the same was true for the load of single diamond particle. By reasonably matching of diamond particles and matrix bond, the abnormal failure efficiency of the diamond particles at the front of the segment was effectively reduced and the wear uniformity of the saw tooth surface was greatly improved. Suggestions on the design of diamond tools and test verification were put forward in the end.     

Micro-Raman and X-ray diffraction stress analysis of residual stresses in fatigue loaded leached polycrystalline diamond discs

Polycrystalline diamond (PCD) cylindrical tool-bits used in oil well drilling are susceptible to fracture due to the hostile environment of randomly occurring high impact loads. These tool-bits generally comprise of a PCD layer sintered onto a Co-cemented tungsten carbide substrate. The cobalt metallic phase primarily aids the formation of the diamond to diamond bonds, however during application the same cobalt expands much quicker than the diamond, breaking the very same bonds it helped to form in the first place, leading to premature failure of the tool bits. As the PCD is virtually a two-phase material comprised of cobalt and diamond, substantial volumes of the metallic phase can be removed through a leaching process without compromising the cohesiveness of the diamond matrix, with reported improved wear resistance and thermal stability. X-ray diffraction and Raman spectroscopy techniques were used to investigate residual stresses in leached polycrystalline diamond disc samples. A systematic investigation and evaluation of the average in-plane residual stress fields using the Raman technique showed a progressive shift of the residual stress state from a compressive stress state to an average tensile stress state as a function of increasing number of loading cycles. In contrast the X-ray diffraction method recorded compressive stresses for all the measurements even at the highest number of loading cycles. The apparent disagreement between the two sets of results were satisfactorily explained by considering the probing beam size and sampling depth for the two different but complementary techniques.     

Abrasive wear behaviour of laser clad and flame sprayed-melted NiCrBSi coatings

In this work, the influence of the processing conditions on the microstructure and abrasive wear behaviour of a NiCrBSi hardfacing alloy is analysed. The hardfacing alloy was applied in the form of coatings onto a mild steel substrate (Fe–0.15%C) by different techniques: laser cladding (LC) and flame spraying (FS) combined with surface flame melting (SFM). In both cases, the appropriate selection of the process parameters enabled high-quality, defect-free NiCrBSi coatings to be obtained. The microstructure of the coatings was analysed by scanning electron microscopy (SEM), with attached energy dispersive spectroscopy (EDS) microprobe, and by X-ray diffraction (XRD). Their tribological properties were evaluated by micro-scale ball cratering abrasive wear tests using different abrasives: diamond, SiC and WC. Microstructural characterisation showed that both coatings exhibit similar phases in their microstructure, but the phases present differ in morphology, size distribution and relative proportions from one coating to another. Wear tests showed that in three-body abrasive conditions, despite these microstructural differences, the wear behaviour is comparable for both coatings. Conversely, in two-body wear conditions with diamond particles as the abrasive, it was observed that the specific wear rate of the material is sensitive to microstructural changes. This fact is particularly apparent in LC coatings, in which the zones of the layers with higher proportions of very small hard particles present a lower wear resistance. These results indicate that it is important to have good microstructural control of this material, in order to obtain coatings with an optimized and homogeneous tribological behaviour.     

喷射共沉积技术在金属结合剂金刚石工具制备中的应用研究

喷射共沉积技术在颗粒增强金属基复合材料的制备中已经有了较为成熟的应用，本文在分析了金属结合剂金刚石工具和颗粒增强金属基复合材料的相似性基础上，研究了利用喷射共沉积技术制备金属结合剂金刚石工具制备的可行性。并通过试验对比分析，探讨了该工艺在金刚石工具生产中的适用性。发现用该工艺试制的试样有金刚石热损耗低、金刚石分布均匀、基体金属对金刚石有较高的把持力、较高的耐磨性和磨削效率等特点。该工艺在大规格、高厚度的金刚石工具制造中会有较高的使用价值。     

M7C3的形态分布对铁基复合层耐磨性能的影响

研究了在电磁搅拌的作用下,硬质相M7C3(主要是(Fe, Cr)7C3和Cr7C3)的数量和形态分布对堆焊层金属耐磨性的影响规律.对堆焊试件进行耐磨、硬度试验,并采用SEM,XRD对堆焊进行显微组织和成分分析.发现随着磁场参数的改变,硬质相M7C3由杂乱无章的分布逐渐转变为较规则的六方块状分布,堆焊层金属的耐磨性也随之增强;当磁场电流为3A,磁场频率为10Hz时,堆焊层金属的性能达到最佳状态,此时堆焊层中硬质相(M7C3)均成较规则的六方块状分布.结果表明,在适当的磁场参数作用下,硬质相(M7C3)成较规则的六方块状分布可以显著的提高堆焊层金属的耐磨性.