Dry Reciprocating Sliding Friction and Wear Response of WC–Ni Cemented Carbides

A number of WC–Ni based cemented carbide grades with distinctive binder contents were tested with the goal to evaluate their dry reciprocating sliding friction and wear behaviour against WC–6 wt.%Co cemented carbide using a Plint TE77 tribometer and distinctive normal contact loads. The generated wear tracks were analysed by scanning electron microscopy and quantified volumetrically using surface scanning topography. The experimental results revealed one WC–Ni grade with superior wear performance.     

WC-10Co-MoS2@Ni自润滑硬质合金与钛合金的摩擦学性能研究

为探究WC-10Co-MoS2@Ni自润滑硬质合金与TC4钛合金的摩擦学性能，通过热压烧结制备不同含量MoS2@Ni的硬质合金试样，采用扫描电子显微镜、三维轮廓仪、维氏硬度计等分析自润滑硬质合金的组织结构和力学性能，利用往复式摩擦试验机研究干摩擦、切削液环境和深冷环境下硬质合金与钛合金的摩擦学性能。结果表明：随着硬质合金中MoS2@Ni含量的增加，表面孔隙减少，力学性能缓慢下降；在干摩擦、切削液环境和深冷环境下，摩擦因数均随MoS2@Ni含量的增加而降低；钛合金和硬质合金在干摩擦时由于钛合金的黏附，阻碍了MoS2发挥润滑作用，磨损形式以黏着和氧化为主；在切削液环境中磨损形式以磨粒磨损和黏着磨损为主，而在深冷环境下减少了氧化和黏着，其磨损形式主要为磨粒磨损，并伴有分层磨损现象。     

Impact of Cr3C2/VC addition on the dry sliding friction and wear response of WC–Co cemented carbides

Two grades of WC–10 wt.%Co cemented carbide with or without addition of Cr₃C₂/VC grain growth inhibitor during liquid phase sintering were produced with the goal to investigate their reciprocating sliding friction and wear behaviour against WC–6 wt.%Co cemented carbide under unlubricated conditions. The tribological characteristics were obtained on a Plint TE77 tribometer using distinctive normal contact loads. The generated wear tracks were analyzed by scanning electron microscopy and quantified topographically using surface scanning equipment. The post-mortem obtained wear volumes were compared to the online assessed wear. Correlations between wear volume, wear rate and coefficient of friction on the one hand and sliding distance and microstructural properties on the other hand were determined, revealing a significant influence of Cr₃C₂/VC on the friction characteristics and wear performance.     

Ti6Al4V/WC-Co干摩擦性能研究

利用Optimal SRV高温摩擦磨损试验机,研究干摩擦条件下钛合金(Ti6Al4V)对硬质合金(WC-Co)的摩擦学性能.研究了载荷、温度与滑动速度对摩擦过程的影响,通过磨损区微观形貌表征分析了磨损机理.结果表明:Ti6Al4V与WC-Co的摩擦系数波动剧烈,产生了严重的黏滑摩擦,且随着载荷、温度与滑动速度的增加,黏...     

ZrN涂层刀具的滑动磨损特性研究

山东大学摘要:采用电弧离子镀法在硬质合金刀具表面制备了厚度为2.19~5.23μm的ZrN系列涂层,测定了涂层的显微硬度,并通过划痕试验和摩擦磨损试验考察了涂层与基体的结合强度及其摩擦磨损性能。在扫描电镜下观察磨损表面形貌,结果表明:ZrN系列涂层能够显著提高硬质合金刀具的表面硬度;涂层与基体的结合强度较高,划痕临界载荷高于60N;与此同时,电弧离子镀法ZrN系列涂层可以显著改善硬质合金刀具的耐磨性能。磨损机理主要是磨粒磨损和涂层的微剥落。     

Edge chipping mechanism and failure time prediction on carbide cemented tool during drilling of CFRP/Ti stack

To investigate the edge chipping during drilling of the CFRP/Ti stack with carbide cemented tools, a drilling experiment was carried out and a tool failure model was proposed. Thrust force, drilling temperature, and tool wear were analyzed. A tool stressing model and a tool failure model of edge chipping were constructed respectively. On the basis of these, the prediction model on the edge chipping was established to forecast the failure time. Drilling temperature, Vickers hardness, and cutting speed were considered during the prediction model building. The results demonstrate that adhesive wear has a great influence on the edge chipping. The damage of adhesive wear for tool rake face leads to the load variation on rake face and the initial crack. Under the action of shear stress, the crack starts at rake face and then expands to the flank face, resulting in tool edge chipping. The affinity interaction (between titanium alloy with carbide cemented) and the thermal residual stress are two critical factors for tool edge chipping. Tear easily occurs inside the binding phase or at the boundary between hard phase and binder phase. As the drilling temperature increases, the hardness of the carbide cemented will gradually decrease. The prediction result of failure time is similar to the experimental result, and the effectiveness of the prediction model is verified.     

Comparison of two test methods for evaluation of forming tool materials

Two test methods often used to simulate the tribological performance of forming tool materials are compared in this investigation through an evaluation of the friction and wear properties of four tool steels in dry sliding. One test (slider‐on‐flat‐surface (SOFS)) utilises a vertical disc sliding on a horizontal flat test surface, and the other (load scanner (LS) tests) utilises two crossed cylindrical rods. The test conditions were selected as equal as possible for the two tests, and the following conclusions are made. Somewhat unexpectedly, the friction and wear results differed substantially between the two tests. The SOFS test showed a better potential to evaluate wear resistance since one test sample is in continuous contact with the other. The LS test can generate higher contact pressures since the two rods contact each other in an unworn condition throughout the whole test stroke. LS indicate that two hard and smooth tool steels tested against each other generally give low friction and good galling resistance. The two hard couples tested sustained the highest loads without any detectable surface damage. For the same combinations of hard steels, SOFS gave a higher friction due to the wear of the disc. The carbides in the disc material resist wear better than the matrix and will consequently wear the disc by abrasion, which adds to the friction. The above conclusions are drawn from a rather limited examination using only one set of test parameters. In fact, the two tests are both very flexible as to the way they can be used, and they both have advantages and limitations in tribological studies. They should rather be considered complementary than competitive. Copyright © 2008 John Wiley & Sons, Ltd.     

Cavitation Erosion and Sliding Wear to Assess Carbide Integrity in AISI D2 Tool Steel

Ultrasonic cavitation and ball-on-disk wear tests were conducted in order to assess the carbide integrity in AISI D2 steel specimens with different heat treatments and carbide orientations on the exposed surface. The response of the tested materials under cavitation erosion was clearly distinguishable for each carbide orientation and heat treatment. Particularly, carbide predominant orientation can be successfully associated with the incubation period of cavitation damage. Validity of the cavitation erosion tests as a useful characterization technique in materials with reinforcement phases is discussed based on the small contact areas associated with the microjets generated in the ultrasonic cavitation test. On the other hand, ball-on-disk tests in conjunction with conventional wear analysis (coefficient of friction graph, wear volume) did not provide a clear relationship between research variables. However, by using discrete Fourier analysis from friction coefficient data, it was possible to establish a correlation between integrity of primary carbide, its orientation and matrix hardness.     

纳米硬质合金刀具切削Al/SiCp复合材料实验

SiC颗粒具有较高的硬度,使Al/SiCp复合材料在切削时刀具磨损剧烈。纳米硬质合金具有较高的硬度、韧性及良好的抗磨损能力。制备了纳米硬质合金刀具WC-7Co,对Al/SiCp复合材料进行了切削实验,研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损,Al/SiCp复合材料的切削实质是断续切削;Al/SiCp复合材料去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%~50%。     

Friction and wear in silicon nitride-steel and cemented carbide-steel pairs in lubricated sliding

Friction and wear tests between a stationary block and a rotating ring under high contact pressure of about 200 MPa were carried out at room temperature under lubrication with a light mineral oil at a sliding distance of 500 m. The block was silicon nitride and cemented carbide, and the ring was bearing steel. The effect of phosphorus and sulphur contained in the mineral oil on the friction, the roughness of the worn surface and the wear of the steel ring is discussed in relation to both pairs. Sulphur was effective in reducing the coefficient of friction of the cemented carbide block-steel ring pair, while phosphorus was successful in decreasing the wear of the steel ring paired with the silicon nitride block. The surface analysis of the steel ring using X-ray photoelectron spectroscopy (XPS) shows that the peak intensities of sulphur or phosphorus beneath the surface depend upon the material of the counterpart, silicon nitride or cemented carbide blocks.     

纳米硬质合金刀具切削Al/SiC_p复合材料的实验

针对SiC颗粒硬度高,切削Al/SiCp复合材料时刀具磨损剧烈,本文提出用具有较高硬度、韧性及良好抗磨损能力的WC-7Co制备纳米硬质合金刀具,并对Al/SiCp复合材料进行了切削实验。研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损;Al/SiCp复合材料的切削实质是断续切削;去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%～50%。实验表明,纳米硬质合金较普通硬质合金更适于加工Al/SiCp复合材料。     

The Role of Atmospheric Oxidation in High Speed Sliding Phenomena—II

An experimental study of the role of oxidation due to frictional heating in unlubricated high speed (13000 ft/min) sliding of metals is discussed. Detailed results for steel on steel have been described in another paper (1). This paper discusses a general picture correlating the results for several metal combinations and also a bonded metal carbide. The results indicate that the oxidation gives considerable protection against surface damage. With copper on copper (previously run-in), copper on steel, and bonded tungsten carbide on bonded carbide relatively little tearing of the metal (or carbide) is observed at light loads. The oxidation should increase with increasing load, and these combinations behave like steel on steel in that on at least one of the surfaces there is, if anything, even less metallic tearing at high load. At low loads wear is mild, in harmony with the oxide protection, but at higher loads severe wear is attributed to disintegration within the oxide itself. With nickel on nickel the oxidation fails to prevent fairly severe metallic tearing even at high loads. Some consequences of these phenomena in the variation of friction, wear and surface damage with load, speed and sample geometry are described.     

基于 STFT 的织构涂层硬质合金表面振动解析方法

针对织构涂层复合工艺对硬质合金表面改性时存在消极振动的问题,提出一种基于织构涂层表面摩擦振动行为的解析 方法来探索织构涂层复合工艺改性效果。 因此,搭建了微织构 AlSiTiN 涂层硬质合金-钛合金磨盘摩擦磨损试验平台,基于短 时傅里叶变换(STFT)与灰度算法对摩擦振动变化规律性映射和振动行为平稳时段进行了获取,进而分析了微织构 AlSiTiN 涂 层工艺参数对硬质合金的改性效果。 试验研究得出了微织构及 AlSiTiN 涂层对硬质合金表面耐磨改性效果最为积极的时间 段,即自接触摩擦起第 5~ 25 min 的稳定作用时期,得出微织构及 AlSiTiN 涂层参数对硬质合金表面改性的影响机理,优选该复 合改性方法抑制硬质合金表面消极摩擦振动的工艺参数,为提升硬质合金表面性能研究提供新思路。     

Wear of a single asperity using Lateral Force Microscopy

This report describes an observation of alternating transitions between linear (Amontons) and non-linear friction-load behavior during Lateral Force Microscope experiments using a silicon tip sliding on a quartz surface. Initially, a transition from linear to non-linear behavior was attributed to nanoscale ‘running-in’ of the tip to form a single contact junction at the interface. Once this had occurred, a non-linear relationship between friction and applied load was observed during a number of loading and unloading cycles. For higher compressive loads, a further transition to a more linear friction-load behavior was attributed to nanoscale wear in the contact zone. Notably, when applied load was reduced below this ‘high-load’ transition point, the same non-linear friction-load behavior was again observed, but with a larger (friction per load) magnitude than seen previously. This cycle was repeated five times in these experiments, and each time, switching between non-linear and linear friction-load behavior occurred, along with a progressive increase in friction (per load) each time load was reduced below the transition point. The progressive increase in friction is attributed to an increased area of contact, caused by nanoscale wear at higher applied loads. An increase in tip size was confirmed by tip profiling before and after experiment. By progressively wearing the asperity at higher loads, the (interfacial or true) contact area, A, between the surfaces could be progressively increased, and as a result, a progressive increase in interfacial sliding friction, F _f , was obtained at lower loads (according to F _f = τA).     

Comparisons of dry sliding tribological behaviors between coarse-grained and nanocrystalline copper

Dry sliding tribological behaviors of nanocrystalline (NC) and coarse grained (CG) Cu were studied by using a ball-on-plate tribometer with a counterface ball of cemented tungsten carbide. The results showed that prior to oxidation and delamination, the steady-state friction coefficients (FCs) of NC and CG Cu are comparable (～0.35). As oxidation with delamination of wear surface occur, the FC for either CG or NC Cu increases gradually, approaching a steady-state FC (～0.63). The wear resistance of the NC Cu was enhanced by at least one order of magnitude under the measured loads ranging from 5 N to 25 N in comparison with the CG counterpart, which is mainly attributed to the higher hardness of the NC layer.     

脉冲磁场处理对硬质合金钻针钻削性能的影响

为提高硬质合金钻针的钻削性能,利用脉冲磁场后处理技术,以0～2T的磁场强度对直径为0.5 mm的硬质合金钻针进行了后处理,对处理后的钻针在印刷电路板上进行了钻孔实验,并分别对钻针的磨损、钻孔质量、微观组织以及力学性能进行了表征。结果表明,在钻削4000和12000个孔后,经过处理后的钻针磨损均显著降低,其中当采用1T工艺时,钻针在钻削4 000个孔后,磨损面积减小了37.97%;而采用2T工艺时,钻针在钻削12 000个孔后,磨损面积减小了38%。经过处理后的钻针钻孔孔径较未处理的钻针波动范围减小,波动范围在0.47～0.5mm之间,而未处理钻针波动范围在0.44～0.49 mm之间,同时1.5T工艺可使孔壁粗糙度减小42%,有效提高孔壁光滑度。脉冲磁处理后钻针的纳米硬度和弹性模量分别提高了26%～116%和40%～312%,且硬度和弹性模量随着脉冲磁场强度的增大而增大。脉冲磁场诱导微观缺陷增殖是钻针钻削及力学性能的提升的主要原因。     

An analytical and experimental investigation of the wear of cemented carbide cutting tools in the presence of dilute organic acids

A simple theoretical analysis of the tool wear process that applies to cutting green wood with cemented carbide tools is described. The analysis, which indicates the important parameters in the wear process, is used to predict the effect of binder volume fraction, carbide particle size, toolworkpiece contact force and the chemical reaction rate constant on wear rate. Comparisons are made between the predicted and experimentally determined wear rates for two types of cemented carbide tools in the presence of weak organic acids. Good agreement, is found that is thought to lend strong justification for the analysis.     

脉冲磁场处理改善硬质合金与钛合金摩擦行为研究

为了改善硬质合金刀具切削加工钛合金的摩擦磨损性能，从而减少钛合金加工中浓缩乳化切削液的用量，利用脉冲磁场对WC-6Co硬质合金进行强化处理，在不同配比切削液润滑下研究磁场处理对WC-6Co/钛合金的摩擦行为的影响。结果表明：磁场处理大幅提高了WC-6Co/钛合金的摩擦性能，且随着浓缩乳化切削液与水配比的降低，摩擦因数明显降低；脉冲磁场处理后，WC-6Co硬质合金/钛合金摩擦后的表面得到强化，黏结相Co的脱落减少。磁场处理后硬质合金磨损性能的改善，是脉冲磁场作用下Co相磁致伸缩对硬质合金的强化效果以及硬质合金剩磁对切削液中油滴吸附的耦合结果。     

Comparison of the wear resistance of selected steels and cemented carbide cutting tool materials in machining wood

An experimental investigation is described where specimens of selected steels and cemented carbides are tested to simulate cutting green wood and cured wood. Extensive results are presented that show quantitatively the progressive wear of several Stellites, steels and cemented carbides as a function of time for sliding under wet and dry conditions.A simple theoretical analysis of tool wear that applies to cutting green wood with cemented carbide tools is described. The analysis, which indicates the important parameters in the wear process, is used to predict the effect of carbide particle size on wear rate. Comparisons are made between the predicted and experimentally determined wear rates for two groups of cemented carbide materials. Good agreement is found between experimental measurements and theoretical predictions. It is shown that wear depends on carbide particle size. Superior wear resistance of cemented carbides is attributed to the high hardness and low chemical reactivity of the carbide phase. The improved wear resistance of the Stellites is attributed to the low reactivity of the matrix.