NiTi SMA/PZT复合材料制备工艺

采用溶胶-凝胶法在经不同表面预处理的NiTi形状记忆合金(NiTi SMA)基体上复合锆钛酸铅(PZT)铁电陶瓷薄膜,利用X射线衍射仪和扫描电镜研究了烧结温度对复合材料的陶瓷层及NiTi SMA基体相组成的影响及NiTi SMA基体表面预处理形貌对其与陶瓷层之间复合结构的影响.结果表明:采用650℃烧结、缓慢冷却得到的陶瓷薄膜层具有单一钙钛矿PZT相结构;表面经过腐蚀预处理的NiTi SMA基体与陶瓷层结合良好.     

高频等离子体中生长碳膜的初探

<正> 碳膜因结构和性能类似金刚石,故也称类金刚石薄膜(Diamond-like Carbon Films)简称“DLC”膜。它具有硬度高、绝缘性能好、红外与可见光透明性好及高化学惰性等特殊性能,而且日益受到人们的重视。如作刀具的超硬涂层,太阳能电池的薄膜层,红外光学系统的抗反射膜,抗腐蚀的化工管道内壁涂层等,具有广泛的应用前景。     

NiTi合金表面改性及其微动磨损性能研究

采用多弧离子镀技术在NiTi形状记忆合金表面制备TiN涂层。利用SRVⅢ摩擦磨损试验机研究NiTi合金表面改性后在37℃Hank’s模拟体液中微动磨损性能,分析法向载荷对TiN合金磨损机制的影响规律。利用SEM扫描电镜及能谱考察磨损表面形貌,结果表明：制备的TiN涂层表面致密均匀,无明显缺陷。说明TiN涂层可有效提高基体的耐磨性能,其磨损机制主要表现为剥落损伤与磨粒磨损并存。TiN涂层显微硬度为784 HV,远高于基体,TiN/NiTi膜基硬度比缓慢下降,涂层与基体结合强度高。     

高性能复杂形状金刚石薄膜涂层刀具的制备和切削性能研究

通过偏压辅助增强热丝化学气相沉积法,采用螺旋形热丝排布方式以及优化的预处理方法和沉积工艺,在硬质合金印刷电路板铣刀的表面沉积了均匀的金刚石薄膜,采用扫描电镜和拉曼光谱研究了金刚石薄膜的表面特征.随后,通过铣削试验研究了金刚石涂层刀具的附着强度和切削性能.试验结果表明,复杂形状金刚石薄膜涂层铣刀既具有附着力强、耐磨性好的特点,同时又具备优异的切削性能,并且其制备无需后续抛光处理就能得到平整光滑的表面,这对于推动金刚石薄膜在复杂形状刀具上的产业化应用具有重要意义.     

NiTi合金涂层的穴蚀过程研究

本文采用磁至伸缩式穴蚀试验机研究爆炸喷涂NiTi合金涂层的穴蚀性能。试验表明，热处理对NiTi合作层的耐穴蚀性能有明显的影响，在180min的试验时间内，穴蚀失重差别可达到2倍。穴蚀形貌观察结果表明，未热处理涂层表现出严重的脱落现象。其原因是适当的热处理工艺可以有效地低涂层的热应力和机械应力，合金元素进行充分的扩散，提高合金成分均匀性，降低相应阻力，提高了NiTi合金涂层的超弹性，从而提高其耐穴蚀性。     

金刚石薄膜涂层刀具切削性能与磨损过程的研究

金刚石薄膜具有高硬度、低摩擦系数、高耐磨性和高导热性能。金刚石薄膜涂层刀具高速干切削硅铝合金可提高生产率。通过金刚石薄膜涂层刀具的切削试验和考察其磨损过程，表明了金刚石薄膜涂层刀具的使用寿命明显高于未涂层的硬质合金刀具，金刚石薄膜涂层刀具的磨损是由薄膜的显微断裂而逐渐脱落的过程。     

纳米涂层的几种制备方法

介绍了纳米涂层和纳米薄膜制备方法的研究进展及其特性。着重对热喷涂制备纳米涂层进行了探讨，认为用热喷涂方法制备纳米涂层具有独特的优越性，具有广泛的应用前景。     

沉积不连续NiTi形状记忆合金薄膜PZT的阻尼性能

在铁电陶瓷锆钛酸铅(PZT)表面沉积不连续的NiTi形状记忆合金(SMA)薄膜,运用XRD、SEM和动态弹性模量测试仪研究了其显微组织及阻尼特性。结果表明:与PZT相比,NiTiSMA薄膜/PZT复合材料的阻尼性能下降;原因是PZT基体与NiTi SMA薄膜在晶化冷却时的收缩不一致导致在PZT基体中靠近薄膜的区域形成了组织异常区,限制了电偶极子的运动,在外界应力作用下薄膜与基体两者的应变不协调加强了异常区对电偶极子运动的限制。     

金刚石涂层刀具的性能评价及应用试验综述

金刚石薄膜与硬质合金基体间的附着力较低一直制约着金刚石薄膜涂层工具的商业化生产和大规模应用。本文对研究中所用各种金刚石涂层刀具性能的评价方法和应用试验进行了综述 ,希望能对评价、提高和改进金刚石涂层刀具产品性能有指导意义。     

纳米表面技术在模具强化中的应用与展望

纳米涂层与纳米薄膜具有良好的硬度、耐磨性、自润性和耐高温性能,是模具表面强化技术中的一种有发展前景的表面处理工艺。从模具的失效分析出发,介绍了目前在模具制造领域中应用较为广泛的几种纳米涂层与薄膜的制备方法和功能特性,并对纳米表面技术在模具表面强化的应用前景作了展望。     

Tribological characteristics of nanosized carbon coatings obtained by the pulsed vacuum-arc method on the modified TiNi surface

Tribological tests of nanosized carbon coatings produced by the pulsed vacuum-arc method on the surface of NiTi premodified by ions of nitrogen and titanium are conducted. The surface modification and formation of a carbon coating 180 nm thick on the surface of a softer material, titanium nickelide, is shown to considerably increase wear resistance and reduce the coefficient of friction.     

Tribological properties of nickel-base nanocrystalline coatings sputter-deposited on austenitic stainless steel

500 nm-thick films are deposited on austenitic stainless steel by neutral (Ar⁺) or reactive (N⁺) ion beam sputtering of Ni or NiTi targets, with (or without) high energy 160 keV-Ar⁺ ion beam assistance. Most of the time the coatings are nanocrystalline and induce a large (excellent in some conditions) increase of the wear resistance. Only Ar⁺ ion beam sputtering of a NiTi target gives an amorphous deposit which does not improve the substrate tribological properties. The hardness and wear resistance of ion beam assisted films are larger than those obtained with non-ion beam assisted coatings. The presence of a hard TiN phase inside a ductile Ni phase, of grains with preferential orientation beneficial to slip, as well as film densification are the main factors which increase the wear resistance. The best results are obtained when the structure is composed of two phases, Ni and TiN. The TiN phase strengthens the already good tribological Ni properties and the Ni ductility induces mechanical accommodation during the friction process.     

Analyzing mechanical properties and nondestructive characteristics of brazed joints of NiTi shape memory alloys to carbon steel rods

Research is being conducted on the use of shape memory alloys, in particular NiTi, in civil engineering, due to the superelastic behavior of NiTi which can be used for damping. In this particular application, NiTi has to be joined to steel, which constitutes a major difficulty due to the considerably different properties of materials involved and the poor weldability of NiTi. Brazing was investigated for this application, since it is an economic and efficient process to joint dissimilar materials. This paper presents a study on the mechanical behavior in the superelastic regime of dissimilar NiTi/steel joints and the feasibility of a nondestructive method based on eddy currents to characterize the weld metal. Brazed joints in lap configuration were produced with a 20 % Ag braze alloy and tested under fatigue conditions in the superelastic regime. Lap joints of steel rods to NiTi ribbons have undergone up to 60 cycles of load/unload without rupture at a maximum load of the superelastic plateau close to the pull-out load of the joint. Measurements of the electrical impedance, with a helicoidal cylindrical coil along the lap joint, allowed the identification of the location of the joint, with a good spatial resolution characterizing the morphology of the brazed joints.     

Fretting wear behavior of superelastic nickel titanium shape memory alloy

The fretting behavior of superelastic nickel titanium (NiTi) shape memory alloy was studied at various displacement amplitudes on a serve-hydraulic dynamic test machine. The results showed that the superelastic properties of the material played a key role in the observed excellent fretting behavior of NiTi alloy. Due to the low phase transition stress (only 1/4 the value of its plastic yield stress) and the large recoverable phase transition strain (5%) of NiTi, the friction force of NiTi/GCr15 stainless steel pair is smaller than the value of GCr15/GCr15 pair and at the same time the Rabinowicz wear coefficient of NiTi plate is about 1/9 the value of GCr15 plate under the same fretting conditions. For NiTi/GCr15 pair, even NiTi has a much lower hardness than GCr15, the superelastic NiTi alloy exhibits superior fretting wear property than GCr15 steel. It was found that the weak ploughing was the main wear mechanism of NiTi alloy in the partial slip regime. While in the mixed regime and gross slip regime, the wear of NiTi was mainly caused by the abrasive wear of the GCr15 debris in the three-body wear mode.     

镍钛形状记忆合金冲蚀磨损研究进展

介绍了材料的冲蚀磨损理论,主要包括微切削理论、薄片剥落磨损理论、变形磨损理论和二次冲蚀理论,分析了冲蚀磨损的影响因素。在综述N iTi合金冲蚀性能研究现状的基础上,对N iTi合金的冲蚀机制进行了分析,认为超弹性及超塑性(形状记忆效应)起到了决定性的作用,除此之外,加工硬化性能、耐疲劳性、马氏体变体的择优取向及自适应性对N iTi合金的冲蚀性能也起到了很大作用。总结了N iTi合金作为耐冲蚀材料在实际应用中存在的问题,为N iTi合金冲蚀性能的研究方向提出了建议。     

第一性原理研究压力下NiTi合金B2相的结构、力学以及热力学性质

运用第一性原理研究0~40 GPa下B2相NiTi合金的机械性能、 电子性质以及热力学性能. 计算发现, 几何优化后NiTi晶体的晶格常数与实验值和其他文献提供的数值大体一致, 表明随着压力的增加该型合金力学稳定且没有相变产生. NiTi合金的体模量B、 剪切模量G和杨氏模量E以及B/G的值随压力增大呈线性增加, 表明压力使其抗体积变形能力、 抗剪变能力及塑性增强. 研究发现, 压力也会使NiTi合金的各向异性发生改变. 对NiTi合金态密度的研究表明, 该合金同时显现出共价性与离子性, 并且压力对其电子性质无明显影响. 此外, 本文还研究了不同温度和压力下NiTi合金的热力学性能, 包括德拜温度ΘD,热容Cv和Cp的变化, 为今后实验提供理论数据.     

An Investigation on Reasons Causing Inferiority in Unlubricated Sliding Wear Performance of 60NiTi as Compared to 440C Steel

60NiTi is gaining recognition as an alternative to 440C steel in ball bearing components due to its intrinsic corrosion resistance and unusually high static load capacity. 440C steel and 60NiTi exhibit comparable Rockwell hardness and would be expected to exhibit similar sliding wear behavior using hardness based models. However, results show that under unlubricated sliding conditions, 60NiTi shows inferior wear properties than 440C steel. In this study, a series of indentation and single pass scratching experiments are conducted to elucidate the reasons behind this unexpected observation. Moreover, sliding wear tests carried out under moderate and extreme tensile stress conditions were used to identify sliding conditions under which these materials exhibit similar and dissimilar behavior. The results show that 440C steel exhibits more microscopic plasticity than 60NiTi, halting the propagation of generated tensile microcracks. In contrast, the intrinsic brittleness of 60NiTi leads to the formation and growth of microcracks between the shear bands causing subsequent wear particle generation. These lead to the occurrence of wear through more aggressive abrasion processes in 60NiTi than 440C steel. These findings help explain why 60NiTi performs well when lubricated. 60NiTi is expected to tolerate ～912?MPa tensile stress before yielding. Under good lubricated conditions where a perfect lubricating film is formed, friction induced tensile stresses fall below the tensile strength of 60NiTi and wear is prevented. However, inadequate lubrication combined with high contact stress leads to damage and wear.     

Effect of surface treatment by ceramic conversion on the fretting behavior of NiTi shape memory alloy

Three types of surface-treated NiTi samples, M-1 (700 °C/0.5 h), M-2 (650 °C/1 h) and M-3 (400 °C/50 h), were prepared by ceramic conversion treatment under different conditions. The effect of the surface treatment on the fretting behavior of NiTi alloy was investigated in the Ringer’s solution by using a horizontal servo-hydraulic fretting apparatus. The experimental results indicated that the surface layer of the low temperature (400 °C) treated samples M-3 was dominated by a single TiO₂ layer, while the high temperature (650 and 700 °C) treated samples M-1 and M-2 consisted of surface TiO₂ layer followed by a TiNi₃ layer. These surface layers were found to have a strong effect on the fretting behavior of the NiTi alloy in terms of changes in the shape of the curves of the tangential force (F _t) versus displacement (d), the fretting regimes and the damage mechanisms involved. The stress-induced reorientation of martensite bands in the NiTi alloy could decrease the slope of the F _t–d curve and thus increase the elastic accommodation ability of the NiTi plate against 1Cr13 steel ball pair. However, since the surface-treated layers could suppress the martensite reorientation in the NiTi substrate and thus decrease the elastic accommodation ability of NiTi, the gross slip started at a smaller displacement amplitude for the surface-treated NiTi samples than for the untreated one. The main wear mechanism of the as-received NiTi alloy in slip regime was adhesion and delamination, while the major damage to the high temperature treated NiTi samples M-1 and M-2 was determined as the spallation of surface-treated layers. Due to the high bonding strength of the surface-treated layer with NiTi substrate, the low temperature treated NiTi samples M-3 showed the best fretting wear resistance in all samples tested.     

A new thermal error modeling method for CNC machine tools

Shape memory superelastic alloys as NiTi have mechanical properties and biocompatibility characteristics quite interesting for a set of industries, amongst which is the medical industry. They find applications in tools and devices where frequently joining between them and to other alloys as austenitic stainless steel is required. However, permanent joining of NiTi to stainless steel is problematic due to the formation of Fe–Ti intermetallics. Pulsed laser welding was studied to join thin foils of NiTi in similar and dissimilar joints to stainless steel. Joining NiTi to NiTi was succeeded with no weld defects. When joining NiTi to stainless steel, it was found that the material impinged by the laser determined the weld pool shape and structure, and it was better when the stainless steel foil was placed below the laser, because nickel enrichment of the weld pool was found to minimise cracking. The factors controlling the weld pool composition and, consequently, the quality of the weld were investigated and discussed.     

多孔NiTi形状记忆合金的制备工艺研究

介绍了制备多孔NiTi形状记忆合金的方法,研究了用粉末冶金法制备多孔NiTi形状记忆合金工艺及过程,结果表明:在140MPa压力下压制,在1223K下粉末冶金制备的NiTi合金,具有合适的孔隙度和较规则的孔形貌。