Surface physical and chemical changes of pure iron after molybdenum ion implantation and their effects on the tribological behaviour I: Physical and chemical analysis

Molybdenum ions generated by a metal vapour vacuum arc (MEVVA) ion source were implanted into pure iron at doses of 1 × 10¹⁷ and 3 × 10¹⁷ ions cm⁻² with an extraction voltage of 45 kV. Auger electron spectroscopy (AES) sputtering depth profiles, X-ray photoelectron spectroscopy (XPS) analysis, X-ray diffraction (XRD) analysis, microhardness and the residual stress of the implanted specimen were studied. The results show that molybdenum atoms exist in the implanted layer at a maximum concentration 20 at.%. A new phase (Fe₃C) is formed in the specimens implanted higher doses due to carbon incorporation during sputtering of the natural oxide film from the implanted surface. The Fe₂Mo phase is formed in both dose regimes. Residual compressive stresses of 310 and 560 MPa were measured on the surfaces of the specimens after molybdenum ion implantation at 1 × 10¹⁷ and 3 × 10¹⁷ ions/cm² respectively due to a local expansion of the lattice in the near-surface region. Due to the existence of residual compressive stress and the formation of the new phases, the microhardness of pure iron specimens was increased from 264 to 325 and 333 kgf mm⁻² by molybdenum ion implantation at 1 × 10¹⁷ and 3 × 10¹⁷ ions cm⁻² respectively.     

离子硫化层与热喷涂硫化层的摩擦学性能比较

分别采用低温离子渗硫和等离子喷涂的方法在45^#钢表面制备了硫化层。在摩擦磨损试验机上对比研究了这两种硫化层在油润滑条件下的摩擦学性能。利用XRD分析了硫化层的相结构，用SEM观察了硫化层的表面及磨面形貌并进行了能谱分析。结果表明，各硫化层的摩擦学性能明显优于原始基体表面，其中离子硫化层的减摩性和耐磨性更好，耐热喷涂硫化层的抗擦伤性更佳。造成这种差别的主要原因在于两种硫化层的成膜机理不同。     

High temperature behaviour of yttrium implanted pure iron and extra low carbon steel

High temperature behaviour of yttrium implanted pure iron and extra low carbon steel were analyzed at T = 700°C and under oxygen partial pressure P _O2 = 0.04 Pa for 24 h to show the benefit of yttrium incorporation to the improvement of the implanted sample corrosion resistance at high temperature. Compositions and structures of yttrium implanted and unimplanted samples were investigated prior to high temperature oxidation studies by several analytical and structural techniques (RBS, RHEED and XRD) to observe the initial yttrium implantation depth profiles in the specimens. High temperature oxidation tests performed by thermogravimetry and by in-situ high temperature X-ray diffraction were carried out with the same experimental conditions on yttrium implanted and unimplanted samples to have reference analyses. The aim of this paper is to show the initial nucleation stage of the main compounds induced by oxidation at high temperature according to the initial sample treatment. The results obtained by in-situ high temperature X-ray diffraction will be compared to those by thermogravimetry to show the existing correlation between weight gain curves and structural studies. Our results allow to understand the improved corrosion resistance of yttrium implanted pure iron and extra low carbon steel at high temperature.     

Study on the Tribological Properties and Composition of W6Mo5Cr4V2 High Speed Steel Implanted by Boron

Boron atoms were implanted into W6Mo5Cr4V2 high-speed steel (HSS) in CC-60 ion implantation machine to improve its tribological properties. The influence of boron implantation dose on the microhardness, friction coefficient and wear resistance of HSS were investigated. The experiment results showed that the implantation of boron can improve the tribological properties of W6Mo5Cr4V2 steel greatly. Then the phase and composition of implanted layer were analyzed by XRD and XPS. The analysisresult revealed that the interface between the implantation layer and substrate appeared to be mixed.With the increase of boron dose, the compound of δ-WB, CrB, BFe3 are the main additive phases, which supposed to be the main reason to improve the tribological properties of W6Mo5Cr4V2 steel.     

Experimental analysis of nanomechanics of spherical titanium oxide nanooils in reducing friction

This work explores the nanomechanics of sphere titanium oxide nanooils in reducing friction between two pieces of cast iron. A friction test is performed using an ATE-77 Reciprocal Tribological Tester made by Cameron-Plint Tribology Limited, England. The friction between two pieces of cast iron was determined 25-135 degrees C using home-made titanium oxide nanooils. In elastohydrodynamic lubrication (EHL), the lubricant is subjected to enormous pressures, there is considerable local heating, and the assumption of constant viscosity no longer holds up. The derivation of the governing equations for elastohydrodynamic lubrication, the pressure and temperature dependence of viscosity is recognized after the lubrication thin film approximation has been made. The viscosity of the nanooils consistently exceeded that of the paraffin oil enlarging the partial EHL area with a complete lubricating film between two move iron surfaces. The spherical geometry of TiO2 nanoparticles caused them to act as a rolling medium when the machine parts move which is in the solid friction area. Because they provide a rolling function, spherical titanium oxide nanoparticles have feasible tribological and lubrication applications in the mechanical industry to reduce noise, vibration and friction wear.     

Tribological properties of sulfurized-nitrided layer prepared by a two-step method

The tribological properties of nitrided layer and sulfurized-nitrided layer of AISI 4135 steel were investigated under oil lubrication, and the layers were prepared by the ion nitriding treatment and a two-step method as the ion nitriding plus sulfurizing duplex treatment, respectively. A ball-on-disc friction and wear tester was adopted to evaluate the tribological performance. Scanning electron microscope (SEM), scanning Auger microprobe (SAM) and X-ray photoelectron spectroscope (XPS) were used to identify the morphologies and chemical compositions of the treated layer and the worn surface. It was presented that the sulfurized-nitrided sample with a thin FeS layer possessed much better tribological behaviors than the nitrided sample, including load carrying capacity, wear resistance, friction reduction and duration time. The mechanism was supposed that the decomposed activated S atoms of FeS layer promoted a new FeS chemical reaction film formation, which induced to the thin FeS layer playing as a solid lubricant for a longer time.     

铝合金基底微碳球作为润滑油添加剂的摩擦学性能及其润滑机理

采用绿色水热制备方法, 以葡萄糖为前身化合物一步制得直径在400~500 nm、尺寸均匀的单分散微碳球, 采用扫描电子显微镜、红外光谱等手段对微碳球的表面形貌及化学特性进行表征, 利用多功能摩擦磨损试验机考察了微碳球作为润滑油添加剂在铝合金-钢摩擦副的减摩耐磨特性, 探讨了微碳球的润滑作用机理。结果表明: 将微碳球作为液体石蜡和商用机油润滑添加剂可以显著提高铝合金-钢摩擦副上的摩擦学性能, 这主要是因为在滑动过程中微碳球可能进入到接触区, 阻止摩擦副之间的直接接触, 并起到纳米滚珠作用。     

The effects of N+ implantation on the wear and friction of type 304 and 15-5 PH stainless steels

Ion implantation of N⁺ into mechanically polished type 304 and 15-5 PH stainless steels was studied to determine its effect on dry wear and friction behavior. Implantation of 4.0 × 10¹⁷ N⁺ cm^-2 at 50 keV yielded a depth profile with a peak concentration of about 45 at.% at a depth of 70 nm which dropped to about 10 at.% at 120 nm. Wear and friction were studied in an unlubricated pin-on-disc configuration using type 304 and 440C stainless steel pins. Both N⁺-implanted steels exhibited reduced wear at low loads but no significant reduction in the coefficient of friction was found. At the lowest normal load studied (12.3 gf), the average maximum wear depth of the implanted 15-5 PH stainless steel disc (about 0.1 μm) was reduced to approximately 10% of that for the corresponding unimplanted pin-on-disc pair after 1000 cycles. At normal loads of 50 gf or above (corresponding to hertzian stresses of 1160 MPa or higher) all beneficial effects were gone. Vacuum heat treatment at 923 K for 1.8 ks of an identically implanted type 304 stainless steel specimen eradicated the benificial effects of the nitrogen implantation. The N⁺-implanted discs show similar reductions in wear to discs implanted with titanium and carbon, but the N⁺-implanted discs do not exhibit the reductions in the coefficient of friction seen with the discs implanted with titanium and carbon.     

MoS2对铜基金属陶瓷摩擦材料性能的影响

研究了MoS2在铜基摩擦材料中的作用,结果表明,作为润滑组元加入的MoS并非以MoS2的形式影响摩擦材料的性能.在烧结过程中MoS2发生了分解反应,分解后的S大部分生成了FeS等硫化物,对材料起润滑作用.随着MoS2含量的增加,材料的耐磨性、稳定系数逐渐提高,而硬度、摩擦系数逐渐降低.     

Investigation on the Tribology of Co Implanted Stainless Steel Using Metal Vapor Vacuum Arc Ion Source

AISI 304 stainless steel was ion implanted with Co, and the tribological property on the surface of the stainless steelwas investigated. The Co ion implantation was carried out using a metal vapor vacuum arc (Mevva) broad-beam ionsource with an extraction voltage of 40 kV, implantation doses of 3×10~(17)/cm~2 and 5×10~(17)/cm~2, and ion currentdensities of 13, 22 and 32μA/cm~2. The results showed that the near-surface hardness of Co-implanted stainless steelsample was increased by 50% or more, and it increased with increasing ion current density at first and then declined.The friction coefficient decreased from 0.74 to 0.20 after Co implantation. The wear rate after Co implantationreduced by 25% or more as compared to the unimplanted sample. The wear rate initially decreased with increasingion current density and then an increase was observed. Within the range of experimental parameters, there existsa critical ion current density for the Co-implanted stainless steel, at which the wear rate decreased     

Surface layer characteristics of ion-implanted metals

Recently ion implantation into metals has been carried out mainly for fundamental studies of non-electronic properties in surface layers such as friction, wear, corrosion etc. Many results have shown that the technique is useful for the improvement of surface layer properties such as wear and corrosion resistance. In this report we describe recent results obtained with the implantation process and the mechanical and chemical properties of implanted iron or iron-based alloys.     

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.     

Erhöhung der Verschleißfestigkeit der TiAl6V4-Legierung durch Implantieren mit Stickstoff-Ionen

Increasing of wear resistance of Ti-6Al-4V alloy by nitrogen implantation Nitrogen ion implantation is used to improve the wear resistance of Ti-6Al-4V alloy. Different implantation doses up to 1 · 10¹⁸N⁺/cm² and E = 170 KeV were used. The unimplanted and the implanted specimens were tested in a wear model system with oscillation loading. The results show, that the wear performance was influenced by implantation dose and also by mean pressure. It was found, that surfaces, which are produced by a high implantation dose (1 · 10¹⁸N⁺/cm²), exhibited greater were resistance than untreated Ti-6Al-4V alloy. The best wear behaviour was achieved by a high implantation dose (1 · 10¹⁸N⁺/cm²) and a low mean pressure (p =0.22 MPa) at the wear test. The difference between the wear rate of the untreated and of the implantated specimen can obtain a factor about 10. The effective depth of the implantation action is greater than the penetration depth of the nitrogen ions.     

莫来石与碳纤维协同填充的聚四氟乙烯基复合材料及其摩擦学性能

为了提高聚四氟乙烯（PTFE）的摩擦学性能,采用机械混匀、带温预压及烧结等工艺制备了莫来石和碳纤维填充的PTFE基复合材料,并通过FTIR、XRD、万能材料试验机、洛氏硬度计、DSC及热机械分析分别表征了PTFE基复合材料的显微结构、力学性能和热学性能;然后,使用MRH-3 型高速环块磨损试验机测定了复合材料的摩擦系数和磨损率,通过自制的硅油砂浆磨损装置测定了复合材料在不同温度下的耐砂浆磨损性能;最后,借助3D测量激光显微镜研究了复合材料摩擦面形貌,并分析了摩擦磨损机制。结果表明:莫来石和碳纤维在PTFE体系中起到填充增强作用,20wt%莫来石-10wt%碳纤维/PTFE复合材料的弹性模量由364 MPa增加至874 MPa;20wt%莫来石-10wt%碳纤维/PTFE复合材料的干摩擦系数较大,但其磨损率与纯PTFE相比降低了3个数量级以上,且此复合材料在水摩擦条件下仍能保持较好的摩擦系数和磨损率,摩擦系数为0.157,磨损率为7.40×10-6 mm3·N-1·m-1;此外,20wt%莫来石-10wt%碳纤维/PTFE复合材料在较高温度下仍能表现出良好的耐砂浆磨损性能。所得结论表明改性得到的PTFE 基复合材料的摩擦学性能显著提高,复合材料可用于有杆抽油井防偏磨。      

两种硫化锑纳米材料在液体石蜡中摩擦学性能的对比研究

利用四球摩擦磨损试验机对硫化锑纳米棒束作为液体石蜡添加剂的摩擦学性能进行了研究. 结合硫化锑纳米颗粒的性能, 对比分析两者作为添加剂润滑下摩擦系数、磨斑直径、钢球磨损表面形貌的变化规律, 并得到以下结论: 两种材料均能在一定程度上改善基础油的减摩抗磨性能, 在低载荷时硫化锑纳米棒束的减摩抗磨性能明显优于纳米颗粒, 较高载荷时, 两者的减摩抗磨性能相当; 就承载能力而言, 纳米颗粒的性能明显优于纳米棒束; 低载时纳米棒束的“微滚珠”效应是其优异摩擦学性能的主要原因.     

He implantation for improved tribological performance in Au electrical contacts

This paper describes the role of He ion implantation on the friction, wear, electrical contact resistance (ECR), and near surface microstructure of Au films. The films were deposited by e-beam evaporation and implanted with He under two different conditions. Electrical contact resistance and friction data were collected simultaneously, while sliding a Au-Cu alloy pin on He ion implanted Au films. Results showed that friction coefficients were reduced from ~1.5 to ~0.5 and specific wear rates from ~4 × 10^?3 to ~1 ×10^?4 mm³/N m (both versus un-implanted samples) without a significant change in sliding ECR (~16 mΩ) as a result of He ion beam implantation. Subsurface microstructural changes due to tribological stress and the passing of current were analyzed using site-specific cross-sectional TEM. The implantation of He by itself did not induce changes to the grain size or crystallographic texture of e-beam Au. However, frictional contact during ECR testing of low energy He implanted films resulted in the formation of stable equiaxed nanocrystalline grains and the growth and redistribution of cavities beneath the wear surface. Plastic deformation as evidenced by transfer of Au to the pin during frictional contact was significantly reduced as a result of implantation. This was hypothesized to be a result of Orowan-like hardening due to He implantation.     

Improved tribological properties of sputtered MoS2 films through N implantation

The effect of N⁺ implantation on the microstructural and tribological properties of r.f.-sputtered MoS₂ films was studied. The cross-section scanning electron micrographs show that, after N⁺ implantation, the loose column structure of the sputtered MoS₂ films increases in density. A decrease in film thickness of about 50% is also observed. The results of X-ray diffraction analysis show that N⁺ bombardment enhances the (100) edge plane orientation of the MoS₂ crystal in the film. The scratch test indicates an improved film-substrate adherence. The tribological test results indicate that N⁺ implantation yields a distinct enhancement in the wear life of the sputtered MoS₂ films. Compared with the as-deposited MoS₂ film, the wear life of the sputtered MoS₂ films implanted with 150 keV N⁺ at 1 × 10¹⁶ N⁺ cm⁻² shows a threefold increase in a relative humidity of 60%–70% and a twofold increase in a vacuum of 5 × 10⁻³ Pa. However, N⁺ implantation inreases the friction coefficient. The lubrication model of the N⁺-modified film is given.     

Tribological behavior of ultra-high molecular weight polyethylene in a hip joint simulator

In this paper effects of various injection molding parameters on tribological properties of ultra-high molecular weight polyethylene (UHMWPE) were investigated. The tribological properties like coefficient of friction and wear rate were obtained from the experimental results of hip simulator which was designed and fabricated in the laboratory. Bovine serum was used as a lubricant in this study. In addition, the hardness of the specimen was also investigated as well. The injection molding parameters that varied for this study are melt temperature, injection velocity and compaction time. The results show that contact loads and melt temperature were mostly influenced the tribological behavior of UHMWPE. A wear mechanism map was developed to study the dominant wear mechanism that influences the wear behavior of UHMWPE. SEM was employed to study the worn out morphologies of UHMWPE. The dominant wear mechanisms that are dominated through our study are ironing, scratching, ploughing, plastic deformation, and fatigue wear.     

Different reinforcement strategies of hybrid surface composite AA6061/(B4C+MoS2) produced by friction stir processing

Aluminum surface composites have gained huge importance in material processing due to their noble tribological characteristics. The reinforcement of solid lubricant particles with hard ceramics further enriches the tribological characteristics of surface composites. In the current study, friction stir processing was chosen to synthesize hybrid surface composites of aluminum containing B₄C and MoS₂ particles with anticipated improved tribological behavior. B₄C and MoS₂ powder particles in 87.5: 12.5 ratio were reinforced into the AA6061 by hole and groove method. Microstructural observations indicated that reinforcement particles are well distributed in the matrix. The hardness and wear resistance of hybrid surface composites improved as compared to the base material, due to well distributed abrasive B₄C and solid lubricant MoS₂ particles in AA6061. The hybrid surface composites achieved ∼32 % increased average hardness as compared to the base material. Hole method revealed ∼13 % better wear resistance compared to the groove method for friction stir processed hybrid surface composite, attributing to an improved homogeneity of particle distribution shown by zigzag hole pattern. Moreover, friction stir processed AA6061 without reinforcement particles exhibited reduced hardness and wear resistance due to loss of strengthening precipitates during multi-pass friction stir processing.     

Change in the properties of BT-23 titanium alloy induced by implantation of iron and zirconium ions followed by exposure to a low-energy high-current electron beam

Atomic physics methods, atomic force microscopy, and testing of microhardness, wear resistance, and friction coefficient were used to investigate Ti₄₁-V₄₁-Al₁₈ samples implanted with iron (60 kV) and zirconium (40 kV) ions, and then exposed to a high-current electron beam with energy fluxes of 2.7 and 5.5 J/cm². The maximum concentration of iron ions is 16.5 at.% at a depth of 85 nm and that of zirconium ions 0.85 at.% at 56 nm. After double implantation, the friction coefficient decreases and the wear resistance increases. After implantation and high-current electron beam treatment, the depth of the hardened layer and the wear resistance increase. Pis’ma Zh. Tekh. Fiz. 25, 66–73 (August 12, 1999)