Plasma Surface Cu Alloyed Layer as a Lubricant on Stainless Steel Sheet:Wear Characteristics and On-job Performance in Incremental Forming

To solve the problems of poor forming and easy adhesion of the stainless steel,Cu alloyed layer on the stainless steels was prepared by the double glow plasma surface alloying technique.The experimentalresults indicated that the supersaturated copper dispersedly precipitated in grain interior and crystalboundaries and formed the vermicular structure.The tribologicaltests indicated that the friction coefficient of the Cu alloyed layer was lower than that of the stainless steels.The wear rate of stainless steelin the presence of Cu alloyed layer was approximately 2-fold lower than that in the absence of the alloyed layer.The results of the incrementalforming indicated that the ploughing phenomenon was not observed on the stainless steelin the presence of Cu alloyed layer during the incrementalforming,while the stainless steelpresented the deep ploughing.Therefore,Cu alloyed layer on stainless steelexhibited excellent self-lubrication and forming properties.

MICROSTRUCTURE AND MECHANISM OF A NEW TYPE OF Ni－Fe－W－P－S WEAR－RESISTANT BRUSH PLATING LAYER

A new type of Ni-Fe-W-P-S wear-resistant brush plating layer isdeveloped, and its microstructure is investigated at different temperatures by usingX-ray diffractometer, transmission electron microscope and surface analytical appa-ratus. The results revealed that the plating layer is composed of amorphous and mi-crocrystalline matrix and intermetallic compounds. Such a microstructure is verybeneficial to improving its wear-resistance.This new type of plating layer can replacethe chromium plating technique which is very poisonous for human health and harm-ful to the agricultural production.

Effect of Micro-addition Rare Earth and Chrome on Friction and Wear Behavior of Boronized layer

Application of powder boronizing to mechanical industry has been restricted because of the brittleness of boronized layer, which inevitably leads to decrease of service life of boronized parts. Therefore, attention should be paid to reducing the brittleness of boronized layer without decreasing its high hardness. In the present paper, a study on the effect of micro-addition rare earth and chrome on friction and wear behavior of boronized layer was carried out using an MM-200 wear test machine. Compared with that of pure single Fe2B phase, the brittleness of the boronized layer containing minim rare earth and chrome elements, obtained by powder RE-chrome-boronizing, is reduced, which results in increasing the bearing capacity and wear resistance of the boronized layer. The friction and wear mechanism is also briefly analyzed.

Wear Performance of Ni/ZrO_2 Infiltrated Composite Layer

The Ni/ZrO2 was used as raw materials to fabricate the surface infiltrated composite layer with 1-4 mm thickness on cast steel substrate through vacuum infiltrated casting technology. The microstructure indicated that the infiltrated composite layer included surface composite layer and transition layer. Wear property was investigated under room temperature and 450 ~C. The results indicated that the abrasion volume of substrate was 8 times that of the infiltrated composite layer at room temperature. The friction coefficient of infiltrated composite layer decreased with the increasing load. The wear resistance of infiltrated composite layer with different ZrO2 contents had been improved obviously under high temperature. The friction coefficient of infiltrated composite layer was decreased comparing with that at room temperature. The oxidation, abrasive and fatigue abrasion was the main wear mechanism at room temperature. Oxidation abrasion, fatigue wear and adhesive wear dominated the wearin~ process under elevated temperature.

Improving wear resistance of magnesium alloy AZ91D by TiN-CrN multilayer coating

Applying a novel method of arc-glow plasma depositing, a 2μm-thick coating with 12 sub-layers of TiN and CrN was deposited alternately on the surface of magnesium alloy AZ91D to improve its wear resistance. The wear behavior was investigated by test of ball on disc sliding. The composition and microstructure of the coating were also analyzed by means of X-ray diffraction (XRD) and glow discharge spectrum (GDS), and the morphology of TiN-CrN film was surveyed through scanning electronic microscopy (SEM) and atom force microscopy (AFM).The adhesion strength between film and matrix was evaluated by ways of stick-peeling test. The surface micro-hardness of the coating is above HK0.011 433, and the specific wear ratio of specimens coated with TiN-CrN films tested decreases greatly compared to that of the bare metal.

基于耦合界面键合效应的石墨烯磨损研究

石墨烯作为二维固体润滑材料,其超滑特性不仅是物理作用结果,其化学键结构机制下的摩擦化学现象,是深入理解石墨烯摩擦性能的关键.本文采用分子动力学(MD)方法构建了多重层数石墨烯增强不同粗糙形貌的金属基底模型,实现了其与金刚石尖端滑动过程的动态分析,揭示了考虑尖端与石墨烯之间存在界面键时石墨烯层的理化耦合作用下的磨损机理.研究结果表明:当考虑金刚石尖端与石墨烯之间化学键合时,石墨烯发生磨损破裂的临界载荷相对于不考虑界面化学键时的值减小,这是由于界面键的形成会剥离石墨烯导致石墨烯断裂所致;金属基底的粗糙度也是决定石墨烯发生磨损破裂时临界载荷的重要因素之一,当粗糙度增大,临界载荷减小,同时通过增加石墨烯层的层数(增韧)来提高石墨烯发生磨损破裂失效的临界载荷.

Friction and wear behaviors of Al_2O_3-13 wt% TiO_2 coatings

Abstract Nanostructured and conventional AlzO3- 13 wt%TiO2 coatings were manufactured by air plasma spray. Friction and wear behaviors of coatings were investigated at room and elevated temperatures using an SRV wear test machine. The nanostructured coating has ＂two regions＂ microstructure, while the conventional coating has typical layered microstructure with obvious interfaces among splats. The coefficient of friction decreases with rising of temperature because of the for- mation of tribo-layer at elevated temperatures. The wear resistance of the nanostructured coatings is higher than that of the conventional coating, and the wear threshold of applied load is 30 N for conventional coating and 40 N for nanostructure coating. The wear resistance difference is related to the ＂two regions＂ microstructure of nanostruc- ture coating, which could blunt or branch the cracks propagation. In our test ranges, the wear rates rising are more sensitive with the applied wear load rising than with the temperature rising.

Sliding Wear of the Hybrid Kevlar/PTFE Fabric Reinforced Phenolic Composite Filled with Nano-titania

The Kevlar/polytetrafluroethylene（Kevlar/PTFE） fabric composite can be used as a self-lubricating liner of the self-lubricating bearing.Many types of nano-particles can improve the tribological performance of the polymer-based composite.Unfortunately,up to now,published work on the effect of nano-particles on the tribological performance of the fabric composite which can be used as a self-lubricating liner is quite scarce.Therefore,for the purpose of exploring a way to significantly improve the tribological performance of the fabric composite,the tribological performance of the Kevlar/PTFE fabric composite filled with nano-titania is evaluated by using the block-on-ring wear tester.The scanning electron microscopy is utilized to observe the morphologies of worn surfaces of the fabric composites and the counterparts.The tensile properties of the composites are evaluated on the universal material testing machine.The test results show that the addition of nano-titania at a proper mass fraction of the matrix resin improves the wear resistance and the tensile strength,decreases the friction coefficient,and makes the wear volume of the composite reach a relative steady state more quickly;plastic deformation and microcutting are important for the wear of the fabric composite;a lubricating layer is formed on the worn surface of the composite during sliding,and the lubricating layer is critical for the tribological performance of the composite;the formation and properties of the lubricating layer are influenced by the nano-titania particles.The proposed study on the effect of nano-titania on the tribological performance of the Kevlar/PTFE fabric composite,especially on the evolution of the worn surface of the composite,provides the basis for further understanding of the influence mechanism of the nano-particles on the tribological performance of the composite and explores a method of improving the tribological performance of the composite.

Evaluation of Microstructure and Wear Properties of Ti-6Al-4V Alloy Plasma Carbonized at Different Temperatures

Ti-6A1-4V （TC4） alloys were plasma carbonized at different temperatures （900, 950, and 1 000 ℃） for duration of 3 h. Graphite rod was employed as carbon supplier to avoid the hydrogen brittleness which is ubiquitous in traditional gas carbonizing process. Two distinguished structures including a thin compound layer （carbides layer） and a thick layer with the mixed microstructure of TiC and the a-Ti in carburing layer were formed during carburizing. Furthermore, it was found that the microstructure and the properties of TC4 alloy were significantly related to the carbonizing temperature. The specimen plasma carbonized at 950 ~2 obtained maximum value both in the hardness and wear resistance.

Microstructures of surface modification layer on Q235 steel produced by laser melt injection of WC

WC powder was injected onto the surface of Q235 steel by laser melt injection (LMI). The influence of process parameters was studied. The microstructure and composition of the coatings were analyzed by SEM, XRD and EDS. The hardness and wear-resistant property of the coatings and Q235 steel were measured. The results show that LMI layer can be achieved only under the condition that process parameters meet the strict requirements. By optimizing the process parameter, excellent coatings can be acquired by injecting WC powder onto the surface of Q235 steel. The microstructure in the coatings is complex, which consists of WC, W2C and M6C(Fe3W3C-Fe4W2C) phases. The difference of Fe3W3C microstructure in different zones of the coatings is obvious. Both the compositions of the reaction layers around the particle and dendrite precipitation carbides in the upper coating are Fe3W3C. The average hardness of LMI layer is above HV 900, which is about four times that of Q235 steel. The friction coefficient of LMI layer is only one quarter that of the substrate, which indicates that the wear resistance of the coatings is enhanced sharply.

Increasing analyzable steel thickness for thin layer activation experiments

The thin layer activation technique(TLA)is very effective in wear analysis for tribological systems where disassembly is costly or impractical.Since its development in the 1970s,TLA has been applied through direct irradiation of solid targets using ionizing particle beams to obtain an activation with a specific profile.This profile is then used to measure wear in a variety of experiments.These experiments rely heavily on how deep the normalized activation occurs.Depths of 30μm to 50μm are obtained for constant activation by the standard method,which for many experiments is sufficient.However,many others would benefit greatly from a 300μm constant activation layer,such as high-performance engines,softer alloys(brakes),and oil transport systems.Achieving this aim was the goal of this paper.First,we needed to find an adequate irradiation line for the TLA technique.Then,another technique/system was developed(the Attenuation Wheel),which would bring the depth of constant activation from 50μm to 300μm.

Friction and wear properties of copper matrix composites reinforced by tungsten-coated carbon nanotubes

Carbon nanotubes （CNTs） were coated by tungsten layer using metal organic chemical vapor deposition process with tungsten hexacarbonyl as a precursor. The W-coated CNTs （W-CNTs） were dispersed into Cu powders by magnetic stirring process and then the mixed powders were consolidated by spark plasma sintering to fabricate W-CNTs/Cu composites. The CNTs/Cu composites were fabricated using the similafprocesses. The friction coefficient and mass wear loss of W-CNTs/Cu and CNTs/Cu composites were studied. The results showed that the W-CNT content, interfacial bonding situation, and applied load could influence the friction coefficient and wear loss of W-CNTs/Cu com- posites. When the W-CNT content was 1.0 wt.%, the W-CNTs/Cu composites got the minimum friction coefficient and wear loss, which were decreased by 72.1% and 47.6%, respectively, compared with pure Cu specimen. The friction coefficient and wear loss of W-CNTs/Cu composites were lower than those of CNTs/Cu composites, which was due to that the interracial bonding at （W-CNTs）-Cu interface was better than that at CNTs-Cu interface. The friction coefficient of composites did not vary obviously with increasing applied load, while the wear loss of composites increased significantly with the increase of applied load.

Microstructures and properties of the nitrided layers fabricated on titanium substrate by direct current nitrogen arc melting technique

The nitrided layers mainly containing TiN dendrites were fabricated by direct current nitrogen arc melting method. The test results show that the layers are harder and more resistant to wear than the titanium substrate. Arc traveling speeds and arc currents have an effect on both the microstructures and the properties of the layers. Decreasing the arc traveling speed or increasing the arc current can obviously enhance the hardness and the wear resistance of the nitrided layers.

超薄磨耗层(Superlayer)配合比设计及施工技术研究

为检验超薄磨耗层(Superlayer)在道路预养护的处治效果,以厦门同集路路面养护工程为依托,选择普通沥青段及桥头搭板混凝土铺装段为试验段,从磨耗层的原材料选择、配合比设计、施工工艺等方面进行研究。研究表明:超薄罩面厚度较薄,适用于一般道路路面病害处治,也适用于对桥梁桥面、隧道路面等受荷载或净空限制的路面病害处治,而且具有显著的经济效益;路面病害经处治后,可延长使用寿命,提高使用质量。

多物理场下超薄吸波磨耗层微波加热性能研究

微波加热技术在沥青路面除冰中的应用得到了广泛的关注,然而目前多对沥青路面整体进行微波加热增强,从而导致路表加热效率提升缓慢。为了进一步提高沥青路面路表的微波加热性能,采用碳化硅(SiC)微波增强集料制备了一种超薄吸波磨耗层,通过微波加热以及除冰试验分析了超薄吸波磨耗层的微波加热性能以及加热耐久性,确定了超薄吸波磨耗层的最佳厚度。并采用COMSOL Multiphysics有限元软件建立了多物理场沥青混凝土微波加热模型,分析了超薄吸波磨耗层的设置对微波加热过程中电磁场的强度与分布以及温度场的影响。研究结果表明:在2.45 GHz频率的微波加热下,超薄吸波磨耗层具有良好的微波加热性能,10 mm厚的超薄吸波磨耗层的微波加热效率相比于普通沥青混合料以及整体微波增强的沥青混合料提高了4.47倍和1.40倍。SiC稳定的微波吸收性能保证了超薄吸波磨耗层具有良好的微波除冰耐久性,在经过反复的微波加热除冰后超薄吸波磨耗层的除冰时间仍然可以保持在45 s左右。数值仿真模拟结果表明超薄吸波磨耗层较强的微波吸收能力可以局部增强试件表层的电磁场强度,从而使更高的温度分布在试件表层。超薄吸波磨耗层内部的电场强度和磁场强度分别比普通沥青混合料试件提高了50.9%和15.7%。综上可知,超薄吸波磨耗层的设置可以提高沥青路面表面的微波加热性能。

Abrasion Behaviour of Boronized Layer

1.IntroductionBoronizing can evidently increase thesurface hardness and wear resistance of me-tallic materials[1].It is simple in technique,not expensive and widely used on tools,diesand some other parts which are easy towear.However the wear mechanism andbehaviour of boronized layer are not clearwhen abraded by mixed abradants such ascoal,hard mineral etc.[2,3].Several metallic materials commonly

Ceramic alloying with Ti-N deposition and diffusion of multi-layers by plasma surface alloying technique

High quality TiN multi-layer was obtained on steel substrate by combined technology of plasma glow discharge sputtering, hollow cathode effect and interfacial diffusion. The TiN multi-layer consists of deposition layer and diffusion layer. Its morphology, structure and chemical compositions were analyzed. The microhardness and wear resistance were measured. The results indicate that the diffusion of Ti and N into the substrate leads to a strong interfacial adhesion. The thickness of TiN multi-layer is about 10μm. The strongest diffraction is on the (200) crystal plane of TiN. The surface hardness is about to 2300(HV_ 0.1). The wear resistance of the TiN ceramic alloying multi-layer is excellent and the friction coefficient is low under dry sliding conditions.

Hardening Effect on Machined Surface for Precise Hard Cutting Process with Consideration of Tool Wear

During hard cutting process there is severe thermodynamic coupling effect between cutting tool and workpiece, which causes quenching effect on finished surfaces under certain conditions. However, material phase transformation mechanism of heat treatment in cutting process is different from the one in traditional process, which leads to changes of the formation mechanism of damaged layer on machined workpiece surface. This paper researches on the generation mechanism of damaged layer on machined surface in the process of PCBN tool hard cutting hardened steel Cr12MoV. Rules of temperature change on machined surface and subsurface are got by means of finite element simulation. In phase transformation temperature experiments rapid transformation instrument is employed, and the effect of quenching under cutting conditions on generation of damaged layer is revealed. Based on that, the phase transformation points of temperature under cutting conditions are determined. By experiment, the effects of cutting speed and tool wear on white layer thickness in damaged layer are revealed. The temperature distribution law of third deformation zone is got by establishing the numerical prediction model, and thickness of white layer in damaged layer is predicted, taking the tool wear effect into consideration. The experimental results show that the model prediction is accurate, and the establishment of prediction model provides a reference for wise selection of parameters in precise hard cutting process. For the machining process with high demanding on surface integrity, the generation of damaged layer on machined surface can be controlled precisely by using the prediction model.

Effect of porosity on wear resistance of SiC_p/Cu composites prepared by pressureless infiltration

The influence of porosity on the wear behavior of high volume fraction (61%) SiCp/Cu composite produced by pressureless infiltration was studied using a sliding,reciprocating and vibrating(SRV) machine.SiCp/Cu composites slid against hardened GCr15 bearing steel ball in the load range of 40-200 N.The results show that the wear rate increases with increasing porosity.The composite containing low porosity shows excellent wear resistance,which is attributed to the presence of mechanically mixed layer on the worn surface.In this case,the dominant wear mechanism is oxidative wear.Comparatively,the composite containing high porosity exhibits inferior wear resistance.Fracture and spalling of the particles are considered as the main causes of severe wear.Third body abrasion is the controlling wear mechanism.In addition,porosity has more important influence on wear rate at high load than at low load.This is associated with the fact that the fracture and spalling of particles is a process of crack initiation and propagation.At lower load,the pores beneath the worn surface can not propagate significantly,while the pores become unstable and easily propagate under high load,which results in a higher wear rate.

High Temperature Wear Characteristics of a New Hot Work Die Steel CH95

High temperature wear characteristics of a new hot work die steel CH95 doped with a small amount of rare earth （ Re ） and boron （ B ） have been investigated and compared with those of conventional die steel H11 at a series of temperatures and loads. Worn surfaces of CH95 steel and H11 steel were analyzed with a scanning electron microscope. It is found that high temperature mechanical properties of CH95 steel are much better than those of H11 steel. The oxide layer formed on the worn surface plays an important role in wear resistance at high temperature. When the load is less than 63 N, the surface oxide layer keeps integrated and the effect of load on high temperature wear is small. When the load is higher than 63 N, the supporting ability of matrix to the oxide layer decreases with the increase of load, which results in an increase of wear rate. Compared with H11 steel, the wear resistance of CH95 steel is much better and the worn surface of CH95 steel is smoother. It is easier for CH95 steel to form a compact and integrated surface oxide layer at high temperature than for Hll steel, which protects the worn surface and reduces wear.