类金刚石薄膜对轴承钢表面机械性能和滚动接触疲劳寿命的影响

使用等离子体浸没离子注入与沉积(PIII&D)技术在轴承钢基体表面合成类金刚石(DLC)薄膜,研究了薄膜的结构和性能,结果表明,所制备的DLC薄膜主要是由金刚石键(sp3)和石墨键(sp2)组成的混合无定形碳,且sp3键含量大于10%,DLC膜层致密均匀,与基体结合良好,DLC膜具有很高的硬度和杨氏模量,分别达到40 GPa和430 GPa;其最低摩擦系数由基体的0.87下降到0.2,被处理薄膜试件在90%置信区间下的L10、L50、La和平均寿命L较基体分别延长了10.1倍、4.2倍、3.5倍和3.4倍,PIII&D轴承钢滚动接触疲劳寿命的分散性得到了显著改善.     

机械滚压对A473M钢疲劳性能的影响

采用机械滚压对A473M马氏体不锈钢轴套材料进行表面处理,研究滚压工艺对其力学性能的影响。采用SEM、白光干涉仪、X射线衍射仪、显微硬度计、EBSD、拉伸试验机和疲劳试验机分别对试样表面形貌、表面粗糙度、残余应力、显微硬度、拉伸性能和疲劳性能进行系统表征。结果表明:滚压加工试样表面的粗糙度明显降低,仅为车削加工的1/5;滚压加工在材料近表面引入残余压应力,其值最高可达946 MPa,沿深度方向逐渐减小,残余压应力层深度约为200μm,表面硬度提高30%左右,硬度影响层深度可达200μm;抗拉强度、屈服强度和伸长率分别提升了40%,22%和8%,疲劳寿命由基体材料的5.4×10^4周次提高到1×10^7周次。采用滚压加工后材料的力学性能明显提升,疲劳寿命显著增加。     

层流等离子体淬火对GCr15轴承钢的滚动接触疲劳及损伤性能的影响

为了提高GCr15轴承钢的滚动接触疲劳(RCF)性能,使用层流等离子体淬火(LPQ)技术对GCr15轴承钢表面进行了四种不同扫描速度(350 mm/min、550 mm/min、750 mm/min、950 mm/min)的等离子体淬火实验。用MJP-30滚动接触疲劳实验机对处理前后的试样进行RCF试验。采用激光共聚焦显微镜(VK-9710)、超景深显微镜(UDM, VHX-1000C, Japan)、扫描电子显微镜分析试样组织结构、成分、微观损伤形貌,对试样进行硬度测试,分析疲劳扩展机理。结果表明：由于LPQ的冷却速率及加热速率较快,试样表面产生淬火硬化区,形成细小的隐晶马氏体组织,表层硬度增大。硬化层厚度影响RCF扩展机理,硬化层厚度越深,疲劳寿命越长,LPQ使RCF寿命延长64%。     

激光冲击强化制备发动机用FGH96镍基高温合金性能分析北大核心CSCD

采用时效工艺处理发动机用FGH96镍基高温合金,利用激光冲击强化方法对其表面进行修复,实验测试分析其组织,残余应力及疲劳寿命。研究结果表明:基体中形成了大量的γ相奥氏体;时效96h后显微组织中产生了大量碳化物,存在沿晶析出。激光冲击强化处理后位于表面附近的晶粒形成更小的尺寸,合金表面晶粒发生明显细化,链状碳化物在晶粒内呈现弥散分布状态,实现FGH96合金的沉淀强化作用,对位错运动产生明显抑制效果。经激光冲击强化处理后试样并未产生新的衍射峰。激光冲击强化可以使试样表面获得更高的残余压应力,使时效试样达到更高的疲劳寿命。激光冲击强化还可以将残余应力引入到基体中,使疲劳裂纹源受到明显抑制,显著降低疲劳裂纹的扩展速度。     

喷丸强化对2XXX铝合金疲劳寿命的影响

研究喷丸对2XXX铝合金拉-拉疲劳性能的影响。对未喷丸试样和喷丸强化试样的微观组织、显微硬度、残余应力和拉-拉疲劳性能进行对比分析。结果表明:喷丸处理后,试样的组织和微结构未发现明显变化,但其粗糙度、残余压应力和显微硬度有所提高,分别是未喷丸试样的6.25倍,3.85倍和1.12倍;拉-拉疲劳性能显著提高,其中值疲劳寿命是未喷丸的1.67倍。在99.9%存活率下,喷丸试样的安全寿命是未喷丸试样的1.45倍。且表面喷丸强化后疲劳裂纹源由多个变为一个。     

激光冲击强化制备发动机用FGH96镍基高温合金性能分析

采用时效工艺处理发动机用FGH96镍基高温合金,利用激光冲击强化方法对其表面进行修复,实验测试分析其组织,残余应力及疲劳寿命。研究结果表明:基体中形成了大量的γ相奥氏体;时效96h后显微组织中产生了大量碳化物,存在沿晶析出。激光冲击强化处理后位于表面附近的晶粒形成更小的尺寸,合金表面晶粒发生明显细化,链状碳化物在晶粒内呈现弥散分布状态,实现FGH96合金的沉淀强化作用,对位错运动产生明显抑制效果。经激光冲击强化处理后试样并未产生新的衍射峰。激光冲击强化可以使试样表面获得更高的残余压应力,使时效试样达到更高的疲劳寿命。激光冲击强化还可以将残余应力引入到基体中,使疲劳裂纹源受到明显抑制,显著降低疲劳裂纹的扩展速度。     

不同温度下等离子渗氮后TC4钛合金的摩擦磨损性能EI北大核心CSCD

采用等离子渗氮技术提升TC4钛合金的耐磨性并探究最优渗氮温度。利用LDM 1-100型等离子渗氮设备,在650,700,750,800,850℃和900℃温度下对TC4钛合金进行渗氮处理,保温时间均为10 h。利用光学显微镜、扫描电子显微镜、白光三维形貌仪、X射线衍射仪和显微硬度计分别对不同温度渗氮试样的微观组织结构、表面形貌、表面粗糙度、相结构和硬度进行表征。利用CETR UMT-3型多功能摩擦磨损试验机测试等离子渗氮后TC4钛合金的摩擦学性能。结果表明:TC4钛合金表面显微硬度和粗糙度随温度升高而增大,在900℃渗氮后TC4钛合金表面显微硬度达到了1318HV 0.05,约为基体(360HV 0.05)的4倍。硬度的升高是由于渗氮后试样表面形成了硬质氮化物相(TiN和Ti2N相),且随着渗氮温度升高氮化物的含量增加。相较于低温渗氮(低于750℃)的试样,850℃和900℃渗氮试样的承载能力显著提升。与原始TC4试样相比,渗氮处理后试样的磨损体积显著降低。当渗氮温度为850℃时,试样磨损体积为未处理试样磨损体积的1.2%(1 N),3.0%(3 N)和62.2%(5 N),试样的耐磨性提升更为显著。     

孔强化对TC18钛合金疲劳寿命的影响

为提高TC18钛合金带孔零件的疲劳寿命,使用基体和焊缝上开孔的TC18钛合金试样,研究孔挤压和孔喷丸强化前后的表面残余应力,孔强化工艺对试样疲劳寿命的影响以及试样疲劳断口.研究表明,对基体和焊缝上的孔进行喷丸强化处理后,孔表面残余压应力值达到-300MPa以上,由于残余压应力和表面完整性的作用,孔喷丸强化效果比挤压强化...     

9Cr18轴承钢表面不同等离子体浸没离子注入强化处理技术研究

采用不同的等离子体浸没离子注入(PⅢ)工艺在9Cr18轴承钢表面进行了气体、金属、金属加气体的离子注入和碳化钛(TiC)、类金刚石(DLC)薄膜的等离子体浸没离子注入与沉积(PⅢD).对处理后的试样进行了X射线光电子能谱(XPS)、X射线衍射(XRD)、俄歇电子能谱(AES)和拉曼光谱(Raman)分析;测试了处理前后试样的显微硬度、磨痕宽度和摩擦系数.结果表明:处理后试样表面均形成了不同的改性层,且改性层中化学组成和各元素的浓度-深度分布随处理工艺的不同而变化;处理后试样的显微硬度都有较大提高,最大增幅达77.7%;表面摩擦系数由0.8下降到0.16;磨痕宽度减少了23倍;与PⅢ工艺相比,相同参数下,PⅢD处理后的试样表面综合性能更加优异.     

氮/氟离子注入Ti6Al4V合金耐磨性研究

通过等离子体基离子注入(PBII)表面改性的方法,采用不同的负脉冲偏压对Ti6Al4V合金进行氮/氟离子注入,并研究了改性层的结构、硬度以及摩擦磨损性能等。利用原子力显微镜研究了改性前后的表面粗糙度变化,并用X光电子能谱分析了改性层表面结构和化学组成,还使用力学显微探针分析试样的硬度,并用球盘式摩擦磨损实验仪和扫描电镜表征了摩擦磨损性能并观察了磨痕形貌。测试结果表明:氮氟离子注入改性试样粗糙度降低,并形成了由Ti O2,Ti F3,Ti F4和Ti N等组成的改性层;改性试样的纳米硬度值较未处理基体提高;氮氟离子注入试样表现出更好的弹性回复行为;改性试样摩擦系数和磨损体积均较基体下降,磨痕形貌从粘着磨损为主转变为磨粒磨损,耐磨性改善;注氟偏压-20 k V的试样获得最理想的性能。     

Wear behaviour and rolling contact fatigue life of Ti/TiN/DLC multilayer films fabricated on bearing steel by PIIID

In order to improve the friction and wear behaviours and rolling contact fatigue (RCF) life of bearing steel materials, Ti/TiN/DLC (diamond-like carbon) multilayer hard films were fabricated onto AISI52100 bearing steel surface by plasma immersion ion implantation and deposition (PIIID) technique. The micro-Raman spectroscopy analysis confirms that the surface film layer possess the characteristic of diamond-like carbon, and it is composed of a mixture of amorphous and crystalline phases, with a variable ratio of sp²/sp³ carbon bonds. Atomic force microscope (AFM) reveals that the multilayer films have extremely smooth area, excellent adhesion, high uniformity and efficiency of space filling over large areas. The nanohardness (H) and elastic modulus (E) measurement indicates that the H and E of DLC multilayer films is about 32 GPa and 410 GPa, increases by 190.9% and 86.4%. The friction and wear behaviours and RCF life of DLC multilayer films specimen have also been investigated by ball-on-disc and three-ball-rod fatigue testers. Results show that the friction coefficient against AISI52100 steel ball decreases from 0.92 to 0.25, the longest wear life increases nearly by 22 times. In addition, wear tracks of the PIIID samples as well as wear tracks of the sliding steel ball were analyzed with the help of optical microscopy and scanning electron microscopy (SEM). The L₁₀, L₅₀, L_a and mean RCF life L of treated bearing samples, in 90% confidence level, increases by 10.1, 4.2, 3.5 and 3.4 times, respectively. Compared with the bearing steel substrate, the RCF life scatter extent of Ti/TiN/DLC multilayer films sample is improved obviously.     

Influence on Rolling Contact Fatigue Life of GCr15 Steel Treated by Plasma Immersion Ion Implantation

Plasma Immersion Ion Implantation (PIII) has been proved to be a useful technique for surface modification of components with sophisticated shape. Based on the results of conventional three-ball-on-rod testing, the rolling contact fatigue (RCF) life of GCr15 steel treated by PIII technique was studied. During the study, nitrogen plasma was generated and the implantation voltage was varied from 20 to 40 kV. The fatigue test results reveal that implantation voltage has a great influence on RCF life. Compared with the untreated sample, N10and N50 (failure probability is 10% and 50% , respectively) life of the sample with the implantation voltage of 30 kv was increased by 58.8% and 223.5% , respectively.     

空间飞轮轴承等离子体浸没离子注入氮层性能研究

研究了氮等离子体浸没离子注入(PIII)技术处理后空间飞轮轴承内圈的摩擦学性能。通过原子力显微镜分析改性前后试样表面形貌,利用X射线电子能谱分析试样表面成分及结构,通过显微硬度计测量改性前后及不同注入时间下试样表面硬度,考察改性前后试样摩擦系数变化情况。结果表明,空间飞轮轴承内圈进行表面注氮后,表面形成Cr-N化合物,形成第二相及固溶强化使得试样表面硬度显著增加,摩擦系数明显减小,耐磨性增加,轴承组件工作电流明显减小。     

Effect of Different Surface Treatment Methods on the Friction and Wear Behavior of AISI 4140 Steel

In this study,the effects of various surface treatments on the friction and wear behavior of AISI 4140 steel have been evaluated.Sample surfaces of AISI 4140 steel were treated by quenching,carburizing,boronizing and plasma transferred arc (PTA) modification.The microstructural characteristics of surface treated steel samples were examined by optical microscopy and scanning electron microscopy (SEM).The mechanical properties of the samples including the surface roughness,microhardness,and abrasive and adhesive wear characteristics were also evaluated.Wear tests were applied by using a block-on-disc configuration under dry sliding conditions.The wear behavior and friction characteristics of the samples were determined as a function of sliding distance.Each sample group was compared with the other sample groups,and it was observed that the carburized samples demonstrated the lowest weight losses;however,PTA-treated samples demonstrated the lowest coefficient of friction in comparison to the other sample groups at the same sliding distance.     

Mechanical and ellipsometry measurements of thin TiN layer prepared by PIII

Titanium nitrides have good mechanical, biomedical and optical properties, therefore they are used to harden and protect cutting and sliding surfaces and as a non-toxic exterior for bio-medical applications. Nitrogen plasma immersion implantation (PIII), in which the diffusion of nitrogen from low pressure r.f. plasma is combined with the implantation of nitrogen ions at energies up to 30 kV, is an effective tool for nitriding titanium and titanium alloys. In this work, samples of pure titanium were nitrided by PIII at different negative high voltage pulses. The properties and the characteristics of the processed samples were evaluated using X-ray diffraction (XRD), Auger electron spectroscopy (AES), ball-on-disk type tribometer, surface profilemeter, and ellipsometry measurements. The results show that, the wear resistance of the untreated sample in comparison to the PIII treated samples is extremely poor and the friction coefficient for the PIII treated samples is decreased to the half value in comparison to the untreated titanium, this attributed to the formation of the solid solution titanium α-Ti(N) and the cubic TiN phases. Ellipsometric measurements were carried out on the PIII treated samples at different negative high voltage pulses. A three layers model was used to fit the calculated data to the experimental ellipsometric spectra. The thickness, surface roughness and refractive index increase with increasing the negative high voltage pulses. The refractive index at 550 nm increases from 1.83 to 2.09 as the negative high voltage pulses increases from 10 to 30 kV.     

Fatigue and internal friction behavior of nitrogen- and neon-implanted copper

The fatigue life and internal friction of neon- and nitrogen-implanted specimens of copper were measured.The fatigue life is found to increase significantly (by about 50%) and scanning electron microscopy shows that the dislocation activity is markedly suppressed. The internal friction results are consistent and show that there is a pronounced overall reduction in the loss at the fatiguing temperature (300 K) owing to a reduction in dislocation mobility.The internal friction results also show the existence of two new internal friction peaks at 150 and 170 K, which are produced by ion implantation. The results indicate that a defect complex may be responsible, rather than a defect dislocation interaction.Ion implantation is also shown to increase the magnitude of the Bordoni peak at about 50 K in previously deformed samples.     

Influence of Surface Nanocrystallization on Ti Ion Implantation of Pure Iron

In order to increase the depth or concentration of Ti ion implantation of pure iron, the surface mechanical attrition treatment(SMAT), which can fabricate a nanometer-grained surface layer without porosity and contamination in a pure iron plate, was used before ion implantation. Ti ion was implanted into the SMA treated sample and coarse-grained counterpart by using a metal vapor vacuum arc source implanter. The changing of depth and concentration of Ti was studied in a function of implantation time.By optical microscopy, transmission electron microscopy and X-ray diffraction, the grain size of the nano structured surface was studied. Micro-hardness, friction and wear behavior of nano surface layers were studied. By energy dispersive X-ray spectroscopy and Auger electron spectroscopy, the chemical composition and concentration of Ti ion in the surface implantation layer were studied. Experimental results showed that the concentration of Ti increased dramatically compared with untreated coarsegrained samples, which is attributed to the existence of higher density of defects(supersaturated vacancies, dislocations, non-equilibrium grain boundaries etc.) and compression stress field in the SMA treated nanocrystallined surface layer. The interaction between the defects and the implanted solute atoms leads to the increment of solid solubility. But the implantation depth showed inconspicuous change. It is shown that the ion range is just relevant to the energy and mass of the ion, dose of injection,the mass and density of target material.     

New plasma surface-treated memory alloys: Towards a new generation of “smart” orthopaedic materials

This paper describes the corrosion resistance, surface mechanical properties, cyto-compatibility, and in-vivo performance of plasma-treated and untreated NiTi samples. Nickel–titanium discs containing 50.8% Ni were treated by nitrogen and carbon plasma immersion ion implantation (PIII). After nitrogen plasma treatment, a layer of stable titanium nitride is formed on the NiTi surface. Titanium carbide is also found at the surface after carbon plasma implantation. Compared to the untreated samples, the corrosion resistances of the plasma PIII samples are better by a factor of five and the surface hardness and elastic modulus are better by a factor of two. The concentration of Ni leached into the simulated body fluids from the untreated samples is 30 ppm, whereas that from the plasma-treated PIII are undetectable. Although there is no significant difference in the ability of cells to grow on either surface, bone formation is found to be better on the nitrogen and carbon PIII sample surfaces at post-operation 2 weeks. All these improvements can be attributed to the formation of titanium nitride and titanium carbide on the surface.