Grindability Evaluation and Fatigue and Wear Behavior of Conventional and Nanostructured Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-13 Wt.% TiO<Subscript>2</Subscript> Air Plasma Sprayed Coatings

In this paper, air plasma spray Al₂O₃-13% TiO₂ coatings were produced by two type of feedstock powders (agglomerated nanostructured and conventional). Mechanical properties of coatings including hardness, toughness, fatigue, and wear behavior as well as grindability of coatings were evaluated and compared. We report that due to the presence of nanostructure zone in microstructure of air plasma sprayed Al₂O₃-13% TiO₂ nanostructure coatings, a significant gain is observed in toughness, grindability, and fatigue lifetime in nanostructure coating over its counterpart conventional coating.     

Evaluation of Ti-Cr-Cu alloys for dental applications

This study examined the characteristics of as-cast Ti-Cr(7–19%)-Cu(3–7%) (all percentages in this article are mass%) alloys to evaluate their suitability for dental applications; studies on the alloy structures and mechanical properties, grindability, and corrosion behavior were included in the investigation. The alloys were centrifugally cast and bench-cooled in investment molds. The x-ray diffractometry of the as-cast alloys bench-cooled in the molds indicated the following phases: α+β+ω in the 7% Cr and 7% Cr+3% Cu; β+ω in the 13%Cr; and β in the 13%Cr+3% Cu through the 19%Cr+3% Cu alloys. The strengths of the binary β Ti-Cr and ternary β Ti-Cr-Cu alloys with 13 and 19% Cr were approximately two times higher than those of CP Ti. The alloy ductility was dependent on the chemical composition and thus, the microstructure. The 7% Cr alloys were extremely brittle and hard due to the ω phase, but the ductility was restored in the 13 and 19% Cr alloys. The hardness (HV) of the cast 13 and 19% Cr alloys was approximately 300–350 compared with a value of 200 for CP Ti. The grindability of the cast alloys was examined using a rotating SiC wheel at speeds (circumferential) of 500 and 1250 m/min. At the higher speed, the grindability of the 13 and 19% Cr alloys increased with the Cu content. The grindability of the 13% Cr alloy with 7% Cu was similar to that of CP Ti. Evaluation of the corrosion behavior in an artificial saliva revealed that the alloys are like many other titanium alloys within the normal intraoral oxidation potential. The wear resistance testing of these alloys also showed favorable results. This paper was presented at the Beta Titanium Alloys of the 00’s Symposium by the Titanium Committee of TMS, held during the 2005 TMS Annual Meeting & Exhibition, February 13–16, 2005 in San Francisco, CA.     

Effects of TaN nanoparticles on microstructure,mechanical properties and tribological performance of PEEK coating prepared by electrophoretic deposition

In order to solve the friction, wear and lubrication problems of titanium, a series of TaN/ployether- ether-ketone (PEEK) coatings were developed by electrophoretic deposition, and the effects of TaN nanoparticles on the microstructure, mechanical properties and tribological performance of coatings were explored. Results manifest that the introduction of TaN nanoparticles into PEEK coatings could improve the deposition efficiency, enhance the resistant deform capacity, increase the hardness, elastic modulus and adhesive bonding strength. Compared with the pure PEEK coating, the friction coefficient of P-TN-3 was greatly reduced by 31.25%. The wear resistance of P-TN-3 was also improved in huge boost, and its specific wear rate was decreased from 9.42×10^-5 to 1.62×10^-5 mm³·N^-1·m^-1. The homogeneous composite TaN/PEEK coatings prepared by electrophoretic deposition were well-adhered to the titanium alloy substrate, TaN nanoparticles could improve the strength of PEEK coating, and provide wear-resistance protection for titanium alloys.     

纳米镍微粒在耐高温陶瓷涂层中的作用

为了提高钛及钛合金高温抗氧化能力,用流涂工艺在工业纯钛上得到含纳米镍微粒的高温超细陶瓷涂层,通过氧化动力学实验及结合力试验,纳米镍微粒在涂层中对涂层-基体的结合及涂层的抗氧化性有着重大作用,试验用光学显微镜(OM)、扫锚电子显微镜(SEM)及X射线衍射(XRD)进行分析,得知纳米镍微粒在涂层中的作用机制.当加入10%(质量分数)的纳米镍微粒时,其抗氧化力及与基体的结合力最佳.     

Formation of a wear-resistant nanocrystalline layer strengthened by TiO2 (Rutile) particles on the surface of titanium

The effect of a thermomechanical treatment including severe plastic deformation under dry sliding friction conditions and subsequent heating in air to 350–650°C with further holding for 1 h on the structure and wear resistance of commercial titanium of grade VT1-0 has been studied. It has been shown that the deformation by friction leads to the formation of a nanocrystalline structure with α crystals 20–100 nm in size in a surface layer of titanium of about 10 μm thick. The heating of titanium deformed by friction at temperatures of 450–650°C for 1 h in air leads to the formation in the surface layer of this material ～10 μm thick of nanocrystalline particles of the titanium oxide TiO₂ (rutile), the volume fraction of which reaches tens of percents, while the dimensions are ～10 nm. The presence in the surface layer of titanium of a nanocrystalline two-phase (α-Ti + rutile) structure leads to a significant increase in the wear resistance of the VT1-0 titanium in pair with steel 40Kh13. This is explained by the enhanced strength of the arising nanocrystalline layer and its positive influence (as of a transition layer) on the reduction of the level of internal stresses that exist at the interface between the titanium oxide TiO₂ and the host metal.     

钛在模拟空间环境下的摩擦学性能

为了明确钛及其合金在空间环境下的摩擦磨损行为,利用中科院兰州化学物理研究所自主研发的空间摩擦学试验系统对钛在模拟空间环境(高真空、原子氧和紫外辐照)下的摩擦磨损性能进行了研究。用X光电子能谱仪(XPS)分析了钛在原子氧辐照后表面元素价态的变化。采用扫描电镜(SEM)对磨损后试样和对偶钢球的磨痕形貌进行分析,利用能量色散光谱仪(EDS)对钢球磨痕元素面分布进行分析,揭示了钛在模拟空间环境下的摩擦磨损失效机理。结果表明:钛在原子氧辐照后表面发生了氧化;钛在大气环境条件下的摩擦磨损机理主要为磨粒磨损和粘着磨损,在高真空、原子氧和紫外辐照模拟空间环境下的磨损机理主要为严重的粘着磨损、磨粒磨损和塑性变形。相比于大气环境条件下,钛在高真空、原子氧和紫外辐照下的粘着磨损加剧,摩擦因数增加。     

激光表面织构形状参数对钛合金摩擦学性能的影响

针对钛合金耐磨性差的问题,利用激光技术在TC4钛合金样品表面刻蚀出具有不同形状、间距和宽度(直径)的织构,基于CSM球盘式摩擦磨损试验机研究织构形状参数对钛合金在油润滑条件下摩擦学性能的影响。利用扫描电子显微镜(SEM)观察钛合金表面织构的微观形貌及磨痕形貌,利用白光干涉仪测试表面织构和磨痕的三维轮廓并通过计算得到磨损率。结果表明,网格型织构的摩擦因数比沟槽型和点阵型织构更小并且更稳定。织构的间距和宽度(直径)等形状参数显著影响钛合金的磨损性能。原始表面抛光钛合金样品磨损率高于表面织构处理后样品,原始钛合金样品的磨损机制主要为磨粒磨损和粘着磨损,而由于表面织构能起到收集磨屑,储存润滑油的作用,从而显著提升了钛合金的耐磨性。     

Evaluation of titanium alloy fabricated using electron beam melting system for dental applications

In recently advanced rapid prototyping and manufacturing methods, one additional process is to use an electron beam to fabricate metal objects by the layer by layer sintering and/or melting metal powder. This method is often called electron beam melting (EBM). This study examined the mechanical properties, the grindability and corrosion resistance of Ti-6Al-4V ELI (extra low interstitial) specimens which were fabricated by the electron beam melting (EBM) process. Dumbbell-shaped specimens and two kinds of plate specimens were prepared using the Ti-6Al-4V ELI powder in the EBM system. The yield strength, tensile strength, modulus of elasticity and percent elongation at a crosshead speed of 0.25 mm/min were tested. The Vickers hardness in interior structures was determined. Grindability was evaluated as volume loss (mm³) when the specimen was abraded using a SiC wheel at 1250 m/min for 1 min. Lastly, corrosion behavior was examined using the dynamic potentiostatic polarization technique in an artificial saliva at 37 °C. As controls, cast and commercial wrought alloys of Ti-6Al-4V ELI and commercially pure titanium (CP Ti) were evaluated. Cast specimens were prepared in a centrifugal casting machine using a MgO based mold. For the cast specimens, all the mechanical properties, grindability and corrosion characteristics were tested. On the other hand, for wrought specimens, only grindability and corrosion properties were tested. The yield and tensile strength of the as-fabricated Ti-6Al-4V ELI specimens without any additional metallurgical treatments were found to be 735 MPa and 775 MPa, respectively. The elongation was 2.3%. These values are well within many of precious and non-precious dental casting alloys.     

CrAISiN涂层与不同材料配副时的摩擦学特性

目的 研究CrAlSiN涂层分别与304不锈钢、TC4钛合金、Al2O3陶瓷和GCr15钢四种不同材料配副时的摩擦学特性.方法 采用阴极电弧离子镀技术在M35高速钢上制备了CrAlSiN涂层,采用扫描电镜(SEM)、显微硬度计、划痕仪、球-盘式摩擦磨损试验仪和3D轮廓仪分别测试了涂层的结构和性能.结果 CrAlSiN涂层与304不锈钢、TC4钛合金和GCr15钢配副时的磨损形式为粘着磨损和磨粒磨损,其中与亲和性高的304不锈钢、TC4钛合金粘着磨损严重.CrAlSiN涂层与不锈钢对磨时,摩擦系数最高,达到0.71;与GCr15钢对磨时,摩擦系数最低,但摩擦系数波动大;与钛合金对磨时,摩擦系数介于两者之间.CrAlSiN涂层与亲和性较差的Al2O3陶瓷之间的磨损形式为磨粒磨损,随着磨损的进行,摩擦系数逐渐降低.结论 CrAlSiN涂层与亲和性较高的材料对磨时,磨损形式为粘着磨损和磨粒磨损,与亲和性较差的Al2O3对磨时为磨粒磨损.     

TC4钛合金表面沉积CrSiN/SiN纳米多层膜在3.5%NaCl溶液中的腐蚀磨损性能

为了研究纳米多层膜的耐腐蚀性能以及腐蚀磨损机理,采用离子源辅助磁控溅射在TC4钛合金表面制备不同调制周期的CrSiN/SiN纳米多层膜。使用扫描电子显微电镜、能谱仪表征涂层的微观结构、腐蚀形貌以及元素分布;使用划痕仪、纳米压痕仪、维氏硬度计测量涂层的膜基结合力、硬度、弹性模量及断裂韧性,采用电化学工作站以及销盘磨损仪测量涂层耐腐蚀性和腐蚀磨损性。结果表明:调制周期为90 nm与360 nm时涂层耐腐蚀性能较好,腐蚀电流密度分别为1.31×10~(-8)A·cm~(-2)和1.20×10~(-8)A·cm~(-2)。此外,调制周期为45nm时,涂层硬度及弹性模量最大,分别为(22.5±0.6)GPa和(226.4±6.3)GPa,且腐蚀磨损率最低,为9.67×10~(-7)mm~3·N~(-1)·m~(-1)。多层膜结构显著改善了TC4钛合金的耐腐蚀及腐蚀磨损性能。     

Tribological evaluation of diamond coating on pure titanium in comparison with plasma nitrided titanium and uncoated titanium

Titanium alloys are characterized by poor tribological properties, and the traditional use of titanium alloys has been restricted to nontribological applications. The deposition of a well adherent diamond coating is a promising way to solve this problem. In this study, the tribological properties of diamond-coated titanium were studied using a pin-on-disk tribometer, and the results were compared with those of pure titanium and plasma nitrided titanium. The tribological behavior of pure titanium was characterized by high coefficient of friction and rapid wear of materials. Plasma nitriding improved the wear resistance only under low normal load; however, this hardened layer was not efficient in improving the wear resistance and the friction properties under high normal load. Diamond coating on pure titanium improved the wear resistance of titanium significantly. Surface profilometry measurement indicated that little or no wear of the diamond coating occurred under the test conditions loads. The roughness of the diamond coating was critical because it controlled the amount of abrasive damage on the counterface. Reducing the surface roughness by polishing led to the reductions in both the friction and wear of the counterface.     

Effect of severe plastic deformation on the structure,microhardness, and wear resistance of the surface layer of titanium subjected to gas nitriding

The effect of severe plastic deformation under dry sliding friction on the structure, microhardness, and wear rate of the VT1-0 titanium subjected to gas nitriding has been studied. It has been shown that this deformation leads to the formation of a nanocrystalline structure with an α-crystal size of 10–100 nm and a microhardness of ～3.1 GPa in a surface layer up to 10 μm thick. The presence of this structure intensifies the saturation of the surface of the titanium with nitrogen in the course of subsequent gas nitriding at temperatures of 650–750°C. The formation of the nitride nanocrystalline TiN phase in the deformed titanium occurs at a relatively low nitriding temperature (700°C) and a short-term holding (2 h). The volume fraction of the nitride phase, which is formed in the layer up to 10 μm thick, reaches a few tens of percent, which leads to an increase in the microhardness of the nitrided surface of the titanium deformed by friction. Preliminary severe plastic deformation has a negative effect on the fatigue wear resistance of the nitrided titanium due to an increased brittleness of the deformed and subsequently nitrided surface layer of this material.     

Tribological properties of titanium aluminides coatings produced on pure Ti by laser surface alloying

Titanium aluminides coatings were in-situ synthesized on a pure Ti substrate with a preplaced Al powder layer by laser surface alloying. The friction and wear properties of the titanium aluminides coatings at different normal loads and sliding speeds were investigated. It was found that the hardness of the titanium aluminides coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating. Friction and wear tests revealed that, at a given sliding speed of 0.10 m/s, the wear volume of pure Ti and the titanium aluminum coatings all increased with increasing normal load. At a given normal load of 2 N, for pure Ti, its wear volume increased with increasing sliding speed; for the titanium aluminides coatings, the wear volume of Ti₃Al coating and TiAl coating first increased and then decreased, while the wear volume of TiAl₃ coating first decreased and then increased with increasing sliding speed. In addition, the friction coefficients of pure Ti and the titanium aluminides coating decreased drastically with increasing sliding speed. Under the same dry sliding test conditions, the wear resistance of the titanium aluminium coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating.     

TA15钛合金碳钨元素激光表面合金化组织及耐磨性能

针对钛合金耐磨性差的问题,利用WC颗粒与TA15钛合金粉末混合采用激光表面合金化技术在TA15钛合金表面成功制得以溶入W元素的β-Ti为基体、初生及共晶TiC/(TiW)C为增强相的表面改性层。结果表明,改性层由于钨元素与碳元素的添加,显微硬度得到提高,耐磨性能提高了2～3倍。TiC/(TiW)C硬质增强相为提高改性层的耐磨损性发挥了重要作用。     

Corrosion and wear behavior of thermally sprayed nano ceramic coatings on commercially pure Titanium and Ti–13Nb–13Zr substrates

Surface treatments and coatings are the practical approaches used to extend the lifetime of components and structures especially when the surface is the most solicited part of the considered engineering component. Hard thermally sprayed coating is one of the most wear resistance coating widely used in many practical mechanical applications. In the construction of articulating parts of medical devices, titanium and its alloys have to be surface coated to improve their tribocorrosion behavior. In this way, the use of porous thermal coatings is known to be a strategy for better binding bone or tissue on femoral stem for example. It is, thus, important to evaluate the corrosion and the wear behaviors of such materials for biosecurity considerations in the human body. In this study, we investigate the behavior of new nano ZrO₂ and Al₂O₃-13 wt.% TiO₂ thermal sprayed coatings on commercially pure (cp)-Ti (grade 4) and titanium alloy substrates. Friction and wear tests against Al₂O₃ balls showed that the wear resistance of Al₂O₃-13 wt.% TiO₂ is better than that ZrO₂ coating. Both plasma sprayings have similar abrasive wear behavior; however, the average friction coefficient is higher for alumina–titania coating. Electrochemical tests, open circuit potential monitoring and potentiodynamic polarization, were performed in simulated body conditions (Hank’s solution, 37 °C). Results showed that corrosion resistance was appreciably higher for alumina–titania coating.     

钛合金切削用磷酸酯类添加剂润滑特性及有机碱复配研究

目的 提高水基润滑液对钛合金的润滑抗磨性能。方法 针对钛合金/硬质合金摩擦副,使用SRV往复式球盘摩擦磨损实验机,测试了常用的三种切削液及四种水溶性磷酸酯溶液的摩擦磨损效果。通过三维白光干涉形貌仪与扫描电子显微镜对磨损表面形貌及磨痕内外能谱进行检测,分析磨损机理及润滑性能,探究对钛合金具有高效润滑作用的水溶性添加剂,并通过有机碱调节溶液的pH,复配适用于钛合金的润滑体系。结果 对铝合金具有很好润滑作用的切削油对钛合金润滑效果很差,而所选水基润滑液效果较好。研究发现,四种水溶性磷酸酯溶液在质量分数为2%时即可对钛合金产生较好的润滑效果,其中,脂肪醇醚磷酸酯（MOA-3P）润滑效果最突出,摩擦系数最低（0.15）,且稳定、粘着磨损最少。通过二甘醇胺及三乙醇胺调节磷酸酯溶液pH至碱性,除支链烷基化磷酸酯（CP-NF-3）溶液外,其他溶液的摩擦系数均有所变大,且波动性增强,而CP-NF-3磷酸酯碱性溶液润滑时,摩擦系数变化很小,稳定在0.2左右。结论 水溶性磷酸酯与适当的有机碱复配的润滑液,可实现对钛合金的良好润滑,用于钛合金水基切削液体系的研发。     

High-speed milling of titanium alloys using binderless CBN tools

The performance of conventional tools is poor when used to machine titanium alloys. In this paper, a new tool material, which is binderless cubic boron nitride (BCBN), is used for high-speed milling of a widely used titanium alloy Ti–6Al–4V. The performance and the wear mechanism of the BCBN tool have been investigated when slot milling the titanium alloy in terms of cutting forces, tool life and wear mechanism. This type of tool manifests longer tool life at high cutting speeds. Observations based on the SEM and EDX suggest that adhesion of workpiece and attrition are the main wear mechanisms of the BCBN tool when used in high-speed milling of Ti–6Al–4V.     

High thickness Ti/TiN multilayer thin coatings for wear resistant applications

Hard coatings like titanium nitride (TiN) normally contain a high degree of internal stress (usually compressive in-plane parallel with the surface) owing to growth defects developed during the deposition process and thermal mismatch effects after final cooling; it is, therefore, difficult to produce single-layer TiN coatings thicker than 6-7 μm, without adhesion problems. In the present study, thick coatings (i.e. > 10 μm) have been achieved by alternate multilayering of TiN with Ti interlayers, leading to a tougher and less-stressed film. However, having a constant distribution of titanium interlayer thickness is not necessarily the best solution to achieve maximum performance in terms of wear resistance and hardness. The residual stress distribution along the thickness is unlikely to be constant with the inner layers being more stressed due to a greater amount of thermal differential strain. Following this guideline, a series of numerical simulations was performed in order to calculate the residual stress through thickness distribution due to the deposition process. Three sets of multilayered Ti/TiN coatings having both constant and variable Ti interlayer thickness were modelled and deposited, using a reactive arc PVD process. Mechanical and tribological properties were characterized using static and depth sensing Vickers micro-hardness indentation tests, rotating wheel (dimpling grinder) abrasive wear tests and Rockwell C adhesion tests. Coating interface characterizations were made by SEM-EDS. Results showed that adhesion can be significantly improved by adopting a titanium through thickness quantity increasing towards the interface: an optimized distribution allows also higher hardness and wear resistance to be obtained, as it requires a lower total amount of titanium to obtain good adhesion properties.     

TC4钛合金表面激光熔覆WC增强镍基复合涂层的组织及耐磨性

为提高TC4钛合金的耐磨性,利用激光熔覆技术(laser cladding,LC)在TC4钛合金表面制备Ni60+50%WC(体积分数)和deloro22(d22)粉末打底+(Ni60+50%WC)2种耐磨复合涂层。采用扫描电子显微镜(SEM)、能谱仪(EDS)以及X射线衍射仪(XRD)来表征涂层的微观结构和物相组成;使用HV-1000显微维氏硬度计、HRS-2M型高速往复摩擦磨损试验机和WDW-100D电子万能试验机来分析涂层的性能。结果表明:2种涂层均由W₂C、TiC、Ni₁₇W₃、Ni₃Ti和Ti_xW_1-x相组成,2种涂层不仅与基体呈现出优异的冶金结合,而且组织均匀致密,没有裂纹瑕疵;由于涂层中存在着原位合成的硬质相和细晶强化共同作用使得涂层硬度显著提高,约为TC4基体的2.82倍;2种涂层的摩擦系数(COF)和磨损量都远低于TC4钛合金基体;Ni60+50%WC复合涂层和d22粉末打底+(Ni60+50%WC)复合涂层的抗剪切结合强度分别为188....     

Effect of high-voltage pulses on the structure and properties of titanium nitride vacuum-arc coatings

Metal Science and Heat Treatment - The structure, the stress-strain state, and the mechanical properties (hardness and wear resistance) of titanium nitride coatings deposited on a substrate by a...