耦合变形摩擦试验

为了研究奥氏体不锈钢带在成形过程中的摩擦及变形特性,设计了一种耦合摩擦和变形的试验装置,在试验中分析了耦合变形量和滑动速度对摩擦系数、表层磨损和接触表层马氏体转变的影响.结果表明,在增加耦合变形量与滑动速度的条件下,钢带试样的摩擦系数随试验时间呈现明显的波动下降;对带试样磨损表面的X射线衍射分析表明,较高滑动速度使摩擦表层转变的马氏体组织增多,由于摩擦表层转变的马氏体组织剥离和产生磨粒磨损导致了摩擦系数的上下波动.     

膨胀蛭石对铜基摩擦材料摩擦磨损性能的影响

采用粉末冶金法制备膨胀蛭石含量(质量分数,下同)分别为0.1%,2%和4%的铜基摩擦材料,利用MM-1000摩擦试验机测定该材料的摩擦磨损性能,并研究膨胀蛭石对磨损机理的影响。结果表明:加入1%膨胀蛭石时,铜基摩擦材料的摩擦因数提高,但随蛭石含量继续增加而逐渐降低。低转速下,加入膨胀蛭石的材料磨损率显著降低,磨损率受蛭石含量的影响较小;在中高转速下,随蛭石含量从1%增加到4%,材料的磨损率逐渐增大。加入膨胀蛭石后材料表面的摩擦膜更光滑,没有出现易疲劳磨损的亚表面。在低转速条件下,含膨胀蛭石的铜基摩擦材料的磨损机制以粘着磨损为主,在中高速条件下,其磨损机制转变为粘着磨损、犁削磨损和疲劳磨损的复合磨损机制。     

固溶处理后7055铝合金的摩擦磨损性能研究

运用高温预析出、单级及双级固溶等方法分别对7055铝合金进行固溶处理,测定运用不同处理方法后试样的硬度及运用不同目数砂纸打磨所得试样的粗糙程度。选择GCr15钢球作为对偶件,在专用机具协助下分析试样的摩擦性能、磨痕外观形貌,解读铝合金的磨损机制。统计并比较结果,发现基于双级固溶处理工艺处理后试样的综合性能最好,硬度值最高,表层粗糙度及摩擦因数对应值均实现最小,试样表层越粗糙,铝合金干摩擦过程中越容易发生黏着、磨料及表面疲劳磨损问题。     

交变振动载荷下Al2O3陶瓷钢摩擦副的摩擦磨损性能

在Al2O3陶瓷/45号钢摩擦副的工作过程中,摩擦副上的载荷不是单一的静载荷加载,而是复杂的振动载荷加载.在新型振动摩擦磨损试验机上采用环一块接触摩擦方式,研究Al2O3陶瓷与45号钢在交变振动载荷条件下的摩擦磨损性能,并与静载荷下的磨损性能进行对比;对陶瓷磨损表面进行扫描电镜观察与能谱分析.结果表明:在于摩擦条件下,交变振动载荷下的磨损量比正常载荷条件下的磨损量要大;交变振动载荷下氧化铝磨损表面产生微裂纹,氧化铝陶瓷的磨损机理是脆性断裂、磨粒磨损和犁沟磨损.在加载交变振动载荷与加载载荷条件下,氧化铝陶瓷磨损表面均覆盖一层金属转移膜,其主要成分为铁的氧化物.     

不锈钢表面条纹织构倾斜角对摩擦性能的影响

利用电加工的方法在不锈钢表面分别制备了垂直织构和倾斜织构两种条纹织构试样,利用UMT-3摩擦磨损仪研究了具有不同倾斜角表面织构试样的摩擦性能,考察了在干摩擦和油润滑条件下摩擦接触副在织构区摩擦系数的变化情况,分析了条纹织构倾斜角对摩擦性能的影响.结果表明,钢球在织构表面区域滑动过程中,摩擦系数经历了一个先降低后增高的过程,即织构的存在导致了摩擦系数的波动.与垂直织构相比,倾斜织构会导致更明显的摩擦系数波动,且波动幅度与织构倾斜方向有关.当摩擦方向与织构倾斜方向相同时,摩擦系数的变化幅度较反方向更大.      

表面机械研磨纳米化GCr15钢摩擦磨损性能研究

利用表面机械研磨处理（SMAT）技术对GCr15钢制备了纳米结构表层。通过X射线衍射及透射电镜分析了其组织结构,利用UMT—2M型摩擦磨损试验机测试了GCr15钢处理前后的摩擦磨损性能。分析结果表明,试验中处理时间为15 min是提高其摩擦磨损性能的最佳工艺条件。磨痕形貌的扫描电镜观察表明,随着磨损深度的增加,主导磨损机制由黏着磨损转变为磨粒磨损。     

高温快速处理对铜基非晶合金摩擦磨损性能的影响

采用铜模吸铸法制备Cu50Zr42Al8非晶合金,并对其进行高温快速处理,通过X射线衍射(XRD)观察分析其组织结构。利用球-盘往复式摩擦磨损试验机进行干摩擦磨损试验,研究铸态Cu基大块非晶合金的摩擦磨损行为及高温快速处理对其摩擦磨损性能的影响。结果表明:经高温处理后的试样均有CuZr2,ZrCu和AlCu2Zr相析出,且析出相体积分数随处理温度的升高而升高。经925℃处理的试样ZrCu相含量减少,而出现了新相Al2Zr3和AlZr3的晶体衍射峰。经825和875℃处理后的试样摩擦性能得到很大提高,当温度继续升高,摩擦性能下降。经825℃处理后的试样摩擦磨损性能最好,磨损面积、磨损率和平均摩擦系数均为最小值1.31×10-4mm2,0.011×10-4mm3·N-1·m-1和0.11;经925℃处理后的试样摩擦性能最差,其磨损面积和磨损率远远超过其他试样,分别为240.83×10-4mm2和2.01×10-4mm3·N-1·m-1。     

不锈钢耦合变形摩擦有限元分析

针对奥氏体不锈钢成形过程中的摩擦磨损问题,设计了一种耦合变形摩擦的试验方法,在实验中分析了耦合摩擦试验中钢带滑动速度对钢板与压头间的摩擦系数的影响。通过对磨损表面进行观察,以及LS DYNA仿真对应力的分析发现：滑动速度的增加引起了剪切应力的增加,钢带试样的马氏体组织转变量随着其滑动速度的增加而增加,并引起摩擦表层马氏体组织磨粒磨损,表面磨损现象加重,且摩擦系数波动减小。     

WC-11Co硬质合金与不同岩石的摩擦磨损特性

在MMU-10型多功能摩擦磨损试验机上采用销盘湿式摩擦方式,研究WC-11Co硬质合金与两种花岗岩摩擦副的摩擦磨损性能,利用扫描电子显微镜观察硬质合金的磨损表面形貌。结果表明:在同一摩擦条件下,硬质合金/高硬度花岗岩摩擦副的摩擦因数较低;当载荷为700 N时,硬质合金/高硬度花岗岩摩擦副的硬质合金磨损质量损失较高,与硬质合金/低硬度花岗岩摩擦副的硬质合金磨损质量损失差约为4%;而在其他低载荷摩擦条件下,两摩擦副的硬质合金磨损质量损失差均在12%左右,这表明在较低载荷作用下,配副材料对硬质合金磨损的影响相对增大;硬质合金/高硬度花岗岩的磨损机理主要为Co粘结相塑性变形、WC晶粒脱落,硬质合金/低硬度花岗岩的磨损机理主要为硬质合金表面的刮擦。     

纳米凹凸棒石对磨损表面的摩擦改性

将主要含有Mg、Al、O、Si等元素的凹凸棒石按质量分数0.5%添加在柴油机润滑油CD 15W/40中,配制成对比油样。分别利用X射线衍射(XRD)与透射电镜(TEM)分析凹凸棒石的物相组成及颗粒形貌,使用环块摩擦磨损试验机进行摩擦实验,借助表面轮廓仪、聚焦离子束扫描电镜(focus ion-beam scanning electron microscope,FIBSEM)、能量弥散X射线探测器(energy dispersive X-ray detector,EDX)及TEM分析试样的磨损量及磨损表面的形貌、元素和物相组成,并探讨磨损表面的摩擦改性机理。结果表明:该凹凸棒石属于一维纳米材料,分散在CD 15W/40润滑油中使摩擦副的磨损量降低约66%,磨损表面光滑;摩擦过程中,纳米凹凸棒石与摩擦副表面发生复杂的化学反应,形成一层厚度约为10~20 nm的摩擦改性层,其物相组成为晶态和非晶态的SiO2和铝硅酸盐,含有Al、Fe、Si、O、C等元素。     

45钢低温电解渗硫表面摩擦性能的研究

采用75%KSCN+25%NaSCN+0.9%K₃Fe(CN)₆+0.1%K₄Fe(CN)₆+2.5%NH₄SCN的盐浴,45钢为正极,高铬不锈钢为负极,190℃±5℃,1 V电压,20 min低温电解表面渗硫方法,在45钢表面形成10 μm FeS渗层,并且用M-2000型磨损试验机,金相技术、SEM及XRD等分析仪考察其摩擦性能。结果表明,采用低温电解工艺方法可以在45钢表面制备质量较好的FeS层,具有明显的减磨作用;干摩擦条件下,渗硫表面的摩擦系数是未渗硫表面的60%,在油润滑条件下,渗硫表面的摩擦系数为未渗硫表面的70%;在一定载荷范围内,随载荷的增大,FeS层减磨作用增加。     

Study on the friction and wear properties of the surface nanocrystallized 1.0C-1.5Cr steel induced by the surface mechanical attrition treatment

Nano-structured layers are fabricated on the surface of 1.0C-1.5Cr steel by using the surface mechanical attrition treatment(SMAT)technology,and the microstructures of the surface nano-crystallization layers are characterized by means of X-ray diffraction(XRD)and transmission electron microscopy(TEM).The friction and wear properties are also investigated by a UMT-2 friction and wear tester.Experimental research has indicated that the average diameter of nanocrystalline grains in the surface layer after being treated for 15 min is in the range of 10-20 nm,and ferrite and cementite grains can not be identified by their morphologies.The wear-resistance of the specimen treated for 15 min has been doubled,compared with that of the matrix due to the grain refinement to a nano-sized scale.The lowest friction coefficient is 0.27,which is for the specimen treated for 30 min,resulting from the dissolution of the cementite phase and the formation of a relative homogenous structure.The SMAT technique for enhancing the wear-resistance of the 1.0C-1.5Cr steel has an optimum processing time,which is in the range of 15-30 min.The dominant wear mechanism of the specimen treated for 15 min changes from adhesive wear into particle wear.     

Friction Stir Processing for Enhancement of Wear Resistance of ZM21 Magnesium Alloy

Present work pertains to surface modification of the magnesium alloy using friction stir processing (FSP). Silicon carbide and boron carbide powders are used in the friction stir processing of the ZM21 Magnesium alloy. Coating was formed by FSP of the alloy by placing the carbide powders into the holes made on the surface. Surface coating was characterized by metallography, hardness and pin-on-disc testing. Friction stir processed coating exhibited excellent wear resistance and is attributed to grain boundary pinning and dispersion hardening caused by carbide particles. Surface composite coating with boron carbide was found to possess better wear resistance than coating made with silicon carbide. This may be attributed to formation of very hard layer coating of boron carbide reinforced composite on the surface of magnesium alloy. In the present work an attempt has also been made to compare the wear behaviour of surface composite layer on ZM21 Mg alloy with that of conventionally used engineering materials such as mild steel and austenitic stainless steel. Wear data clearly shows that wear resistance of friction stir processed composite layer is better than that of mild steel and stainless steel. This work demonstrates that friction stir processing is an effective strategy for enhancement of wear resistance of magnesium alloys.     

Friction Stir Surfacing Route: Effective Strategy for the Enhancement of Wear Resistance of Titanium Alloy

Titanium alloys are widely used in aerospace applications due to their properties like high strength to weight ratio, good corrosion and creep resistance. Poor wear resistance of these alloys limits their use in tribological applications. Friction surfacing technique is now recognized as an effective solution to surface engineer the light weight high strength alloys to make them suitable for general engineering applications involving wear and corrosion. The present work pertains to a study on wear resistance of surface coating of boron carbide on Ti–6Al–4V alloy using friction surfacing technique. Coating was formed by placing the boron carbide powder into the holes of predetermined depth on the surface and was characterized by metallography, electron probe micro analysis and dry sliding wear testing. The present study revealed that titanium alloy could be friction surfaced with boron carbide powder. The coating exhibited excellent wear resistance, which is attributed to the formation of strong metallurgical bond with the substrate. In the present work an attempt has also been made to compare the wear behaviour of surface composite layer on titanium alloy with that of conventionally used engineering materials such as mild steel and austenitic stainless steel. Wear data clearly revealed that wear resistance of friction stir surfaced composite layer is better than that of mild steel and stainless steel. This study demonstrated that friction stir surfacing is an effective strategy for the enhancement of wear resistance of titanium alloys.     

氮气、空气条件下炭/炭复合材料的摩擦磨损性能

在MM-1000型摩擦试验机上,对炭/炭复合材料分别在氮气和空气中模拟正常着陆能量条件下的摩擦磨损行为进行测试。结果表明:在氮气中,炭/炭复合材料的摩擦因数较高,达到0.32～0.4,磨损率较低,质量磨损率为18 mg/次,线性磨损率为1.4μm/次;在空气中,材料的摩擦因数较低,为0.2～0.3,但磨损率较高,质量磨损率为48 mg/次,线性磨损率为3.8μm/次。磨损表面及磨屑的SEM形貌表明:在空气中,材料摩擦表面易形成炭纤维、基体炭相互脱离的磨屑,其主要磨损机制为氧化磨损;在氮气中,则有纤维与基体炭连接良好、大尺寸的磨屑出现,主要磨损机制为磨粒磨损和粘着磨损。     

High Strength Stainless Austenitic CrMnCN Steels ‐ Part II: Structural Changes by Repeated Impacts

Phase transformations and changes in the structure caused by impact loading of steel Cr18Mn18CN alloyed with carbon+nitrogen are studied in comparison with Hadfield steel using X‐ray diffraction, Mössbauer spectroscopy and TEM. It is shown that the surface layer of all the studied steels impacted by mineral particles of greywacke remains austenitic, although their magnetic structure within a depth of about 10 μm is similar to that of martensite. TEM studies reveal a mixture of amorphous, nanocrystalline and thin‐twinned fcc crystal structures. The suggestion is made that the atomic configuration at the twin boundaries is similar to that in the bcc lattice and induces the high‐spin state of the iron atoms in the thin twins. At the same time, the amorphous structure of the surface layer can be also a source of ferromagnetism like this occurs in rapidly quenched FeSiB ribbons. The extremely high wear resistance of the newly developed CrMnCN steels and of Hadfield steel seems to be related to the impact‐induced surface structure in its amorphous + nanocrystalline + thin‐twinned austenitic states.     

20CrNi2Mo钢干摩擦磨损行为及次表层马氏体形变

 利用MMU-10试验机,在0.13 m/s的速度下,分组对20CrNi2Mo盘环对摩试样进行100、120、150 N接触载荷下的干滑动摩擦磨损试验。采用SEM、EDS、EBSD表征摩擦磨损后环试样表面和截面的形貌及元素。结果表明,接触载荷为150 N时摩擦因数最低、磨损量最大。摩擦热导致磨损表面出现严重的氧化和脱落材料焊结现象,磨损机制由氧化磨损、磨粒磨损和黏着磨损构成。磨损导致了次表层组织变化,出现严重塑性形变层和马氏体形变层。截面EBSD分析结果反映了表层至次表层的应变,EBSD菊池花样质量从表面朝深度方向逐渐提升,采用EBSD图像分割处理及Band Contrast平均值求解可准确找出磨损导致的形变层终止区域。     

Dry Sliding Oxidative Wear in Plain Carbon Dual Phase Steel

 To investigate the tribological potential of the dual phase (DP) steel as a wear resistant material, the wear and the friction characteristics of this steel, which consists of hard martensite islands embedded in a ductile ferrite matrix, have been investigated and compared with those observed in plain carbon hardened (H) steel that has the same carbon content of 02%. Dry sliding wear tests have been carried out using a pin on disk wear testing machine at different normal loads of 213 N, 285 N, 357 N, and 426 N and at a constant sliding velocity of 120 m/s. The analysis of surface and wear debris of samples showed that the wear mechanism was mainly mild oxidative. The friction and the wear rate of the H steel and the DP steel have been explained with respect to the microstructure and the wear mechanism.