钛合金激光熔覆的研究现状与发展趋势

钛合金具有高比强、良好的耐蚀性能等优点,但其耐磨性差,限制了它在摩擦机构的应用.激光熔覆技术是近年来发展起来的一种新型表面改性工艺.在钛合金表面进行激光熔覆,可提高钛合金的表面性能,获得高硬度、耐磨性能好、低摩擦系数的熔覆层.简要阐述了钛合金表面激光熔覆的研究现状,包括激光熔覆工艺、熔覆层的组织与性能,指出了存在的问题,并展望了钛合金激光熔覆的发展方向.     

TC4钛合金表面激光熔覆NiCrCoAlY-Cr3C2复合涂层的摩擦和高温抗氧化性能

为了提高TC4 钛合金表面摩擦磨损和高温抗氧化性能,以 NiCrCoAlY+20%(质量分数)Cr3 C2 混合粉末作为熔覆粉末,采用激光熔覆技术在TC4 钛合金表面制备NiCrCoAlY-Cr3 C2 复合涂层,利用OM,SEM,XRD,EDS等分析涂层的显微组织和物相组成;采用 HXD-1 000TB 显微硬度计测量涂层显微硬度;采用 MMG-500 三体磨损试验机与 WS-G1 50 智能马弗炉对涂层和基体进行摩擦磨损及高温抗氧化实验.结果表明:利用激光熔覆技术在 TC4 钛合金表面可以制备形貌良好、无裂纹和气孔等缺陷的复合涂层.熔覆区显微组织结构致密,多为针状晶和树枝晶;结合区的显微组织主要由平面晶、胞状晶和树枝晶组成,生成了多种可提高耐磨性和高温抗氧化性的碳化物、氧化物和金属间化合物.复合涂层的最高显微硬度为 1344HV,约为钛合金基体 350HV的 3.8 倍;复合涂层的摩擦因数为0.2～0.3,较钛合金基体的摩擦因数0.6～0.7 明显下降;相同条件下复合涂层的磨损失重为0.00060 g,是钛合金基体磨损失重 0.06508 g 的0.9%;恒温 850 ℃氧化 100 h后复合涂层氧化增重为 6.01 mg·cm－2 ,约为钛合金基体氧化增重 25.10 mg·cm－2的24%.激光熔覆技术有效改善了TC4 钛合金表面的摩擦磨损和高温抗氧化性能.     

人工椎间盘关节材料表面耐磨改性研究进展

钛合金和超高分子量聚乙烯(UHMWPE)在人工椎间盘关节材料配对中一般是软体材料,其表面改性对提高假体耐磨性能及长期稳定性有重要意义。主要介绍了采用热处理、微弧氧化、表面渗元素、表面镀DLC膜、激光表面改性、离子注入技术提高钛合金表面硬度和耐磨性的研究进展,以及采用表面镀DLC膜等提高UHMWPE表面硬度和耐磨性的研究现状,展望了人工椎间盘假体耐磨性研究的发展趋势。     

钛合金表面激光熔覆的研究进展

钛合金具有密度低、比强度高、耐蚀性好等优点,广泛应用于航空航天等领域,但钛合金耐磨性低、抗高温氧化性差的特点限制了其应用。利用激光熔覆技术提高钛合金表面性能已成为钛合金表面改性的研究热点。综述了目前国内外钛合金表面激光熔覆材料的研究进展,分析了激光熔覆技术的应用范围,并展望了其今后的发展趋势。     

BT20钛合金表面渗氧研究

氧与钛之间的亲合力比较高,利用这一点可以通过热处理的办法对钛及钛合金部件表面的硬度和耐磨性进行提高.将激光处理的和未经激光处理的BT20钛合金放置在一种特殊固体介质中于大气气氛下进行渗氧处理,来研究炉的加热条件和前处理过程对显微组织和硬度的影响.激光处理过的和未经激光处理的BT20钛合金在相同温度和处理时间的条件下进行渗氧以获得强化层.处理后外层为金红石型的TiO2,里层为由α-Ti组成的氧固溶强化层.激光处理的试样在渗氧后表面硬度最高可达到Hv628,厚度可以达到35μm,而未经激光处理的钛合金的表面硬度最高可以达到Hv580,膜厚度达到25μm .     

激光维持等离子体钛合金表面渗氮研究进展

钛合金具有强度高、密度小等诸多优点,在航空航天等行业具有广阔的应用前景,但是硬度低和耐磨性差限制了其进一步应用。利用物理气相沉积(PVD)和化学气相沉积(CVD)等方法可提高钛合金表面硬度和耐磨性,但是这些方法存在效率低等缺点。钛合金表面激光气体渗氮可快速提高钛合金表面硬度和耐磨性,但是渗氮工艺复杂,需要解决很多科学和技术问题。国内学者开始重视此方面研究,国外学者的研究已经取得了一些成果,目前的研究热点是渗氮过程的机理和等离子体对渗氮过程的影响。最近几年,国外学者采用高速摄像配合不同波长的透镜对等离子体进行系统化拍摄研究,对氮等离子体产生的条件以及等离子体对能量传输、防止渗氮层氧化、增加渗氮层氮含量的作用有了较深入的认识。目前的研究认为氮离子对激光渗氮是有益的,并且等离子体是实现高质量渗氮的核心。在以上研究的基础上,发展了激光维持等离子体渗氮方法,该方法采用激光诱导产生氮等离子体,并在大激光功率、大离焦距离和大扫描速度的工艺参数下渗氮;进一步研究了离焦距离、扫描速度及氮氩比例等工艺参数对激光维持等离子体渗氮过程的影响。激光维持等离子体渗氮层容易开裂,为解决渗氮层开裂问题,发展了两步法激光维持等离子体渗氮方法:第一步激光诱导产生氮等离子体,实现基体大量渗氮;第二步在氩等离子体中用激光重熔渗氮层,消除裂纹。两步渗氮法增强了对渗氮层性能的控制能力,可使得渗氮层性能更优。另外,对渗氮过程进行了定量研究,发现激光扫描速度与钛合金表面熔池存在时间呈线性关系,并且激光扫描速度与渗氮层氮含量呈线性关系,渗氮层硬度和树枝晶含量也呈线性关系;最后研究了两步法激光维持氮等离子体渗氮层的耐磨性,提出渗氮层耐磨性增强的机理。本文综述了激光维持等离子体钛合金表面渗氮的研究进展,分别介绍了等离子体的作用,激光维持等离子体渗氮方法,两步法激光维持等离子体渗氮方法,提出了未来亟需解决的重点问题及有效的研究方法,为未来的研究工作提供参考。     

钛合金表面激光熔覆Ti/Al/B4C/C涂层组织与性能分析

针对钛合金硬度低和耐磨性差的特点,采用激光熔覆技术在TC4钛合金表面制备Ti/Al/B4C/C熔覆层,利用XRD、SEM、EDS探究熔覆层微观组织,并测试熔覆层对TC4钛合金表面硬度及耐磨性能的影响。结果表明:Ti/Al/B4C/C熔覆层中由于形成Ti B、Ti B2、Ti C等硬质陶瓷相及Ti-Al系金属间化合物和Ti3Al C相,相比于基体具有高的硬度和优异的耐磨性。熔覆层硬度在1 100～1 720 HV之间,较基体提升了2～3倍,其体积磨损率约为(2.29～4.18)×10-6mm3/(N·mm),较基体降低了14%～53%,其中以Ti∶Al∶B4C∶C=57∶20∶18∶5(质量比)混合粉末形成的熔覆层性能最好。     

钛合金表面激光熔覆Ti/Ni+ZrO_2涂层的组织与性能

为提高TA15钛合金的表面硬度和耐磨性,采用激光熔覆方法在钛合金表面制备了Ti/Ni+5%ZrO_2涂层(质量分数),并对其组织和性能进行了研究。结果表明:熔覆层与基体结合良好;熔覆层中除了有Ti2Ni和TiNi金属间化合物之外还有少量的单斜相氧化锆(m-ZrO_2)和四方相氧化锆(t-ZrO_2);熔覆层中主要生成相TiNi和Ti2Ni可以极大地提高熔覆层的耐磨性和硬度,ZrO_2相在提高熔覆层韧性的同时,进一步提高了熔覆层的耐磨性和硬度。     

铁含量对激光熔覆层微结构及性能的影响

为满足不同支承辊再制造表面硬度需求,利用激光熔覆技术,将添加不同含量纯铁粉的铁基合金粉末材料熔覆到Cr5支承辊钢表面。研究了铁含量对熔覆层微结构及性能的影响。结果表明,所有材料设计成分条件下熔覆层的截面组织差异很小,均为鱼骨状枝晶和网状晶间组织。通过改变添加铁粉的量可以控制熔覆层中枝晶含量。随着合金粉末中铁含量增多,激光熔覆层截面硬度和耐磨性显著下降。添加50%(质量分数)纯铁粉的粉末材料可以制备出硬度约为480HV、耐磨性高于传统淬火工作层的激光熔覆层,可以满足Cr5支承辊再制造需求。     

表面处理技术对钛合金疲劳性能影响的研究进展

针对钛合金表面硬度较低、耐磨性较差、易高温氧化等缺陷,选择适当的表面处理技术能够使其得以改善。由于钛合金对疲劳性能十分敏感,在表面处理过后,对其疲劳性能有较大影响。因而本文归纳了钛合金表面处理的多种方法,如电镀、化学镀、热喷涂、激光处理、阳极氧化、微弧氧化、物理气相沉积技术等。根据钛合金疲劳断裂现状及表面改性技术的特点,讨论了表面技术的应用、材料的选择和结构的设计对钛合金基体疲劳性能的影响。分析并总结了涂层在疲劳断裂过程起到的作用及影响疲劳性能的的主要原因,展望了未来钛合金表面改性方法、涂层材料及结构的研究趋势。以期为制备高强度、耐摩擦磨损和提升钛合金基体疲劳性能的表面改性涂层提供参考。     

Hardening of 316L stainless steel by laser surface alloying

The goal of this study is to investigate different hardening routes for 316L stainless steel by laser surface alloying. We have investigated the formation of iron-chromium carbides by SiC or carbon incorporation, the alloying with submicronic particles of TiC and the precipitation of titanium carbide from mixtures of Ti and SiC. For each hardening route we present the microstructures and the hardness of the processed surface alloys and the conditions leading to the best compromise between highest hardness, best homogeneity and lowest occurrence of cracks. From these results it can be reasoned that hardening by iron-chromium carbides is the best hardening route and that this surface alloy might be a good candidate for tribological applications.     

Zunderverhalten und Ausscheidungshärtung von hochkarätigen Gold-Titan-Legierungen

The behaviour of oxidation and precipitation hardening of very goldrich gold-titan alloys The oxidation behavior of gold rich Au-Ti alloys with contents of titanium between 0.5 und 1.3 weight-% was investigated in synthetic and natural air in dependence on the oxidation temperature and time. A closed homogeneous layer of titanium oxid was not formed. The nucleation of TiO₂ (Rutil) starts at prefered sites (grain boundaries, structure defects) below the surface of the alloys. The precipitations grow without formation a gapless cover of the grain boundaries. Between the precipitations the concentrations of titanium and oxygen are zero. The titanium is transported out of the interior of the specimen by volume diffusion. Based on an experimentally observed linear relationship between the oxygen uptake and the oxidation time the speed constants could be determined for 750°C, 825°C and 900°C. Between the natural logarithm of the speed constant and the reciprocal temperature a linear connection exists. For this reason it is possible to calculate the kinetics by a well-defined mathematical expression for the speed constant of the titanium oxidation in dependence on the titanium content and the oxidation temperature. The connection between the speed constant and the optical outfit of the surface is illustrated. Furthermore the precipitation hardening of the alloys at temperatures between 100°C and 700°C is described. A noticable increase of the hardness is already produced at relatively low temperatures. Whith increasing temperatures the hardness maximum is shifted to shorter times. With increasing titanium content the hardness maximum increases and it is obtained after shorter times. Cold working before the ageing, raises the hardness maximum and accelerates the precipitation. The precipitations are formed to little plates with high coherency to the matrix preferentialy at the grain boundaries. X-ray analysis sensitively responds to the kinetics of precipitation and gives reliable information about the concentration variations of the matrix. The results concerning the oxidation behavior and the precipitation hardening make it possible to find the conditions of an optimized heat treatment with high hardness but without negative changes of the surface.     

Surface hardening of biomedical Ti–29Nb–13Ta–4.6Zr and Ti–6Al–4V ELI by gas nitriding

The microstructure and hardness near the surface of a biomedical titanium alloy, Ti–29Nb–13Ta–4.6Zr (TNTZ), subjected to gas nitriding at 1023–1223 K was investigated in comparison with the conventional biomedical Ti–6Al–4V ELI (Ti64). After gas nitriding, the microstructure near the specimen surface was observed by optical microscopy, X-ray diffraction (XRD), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). In both alloys, two types of titanium nitrides (TiN and Ti₂N) are formed and the phase is precipitated by gas nitriding. Furthermore, the oxygen impurity in the gas nitriding atmosphere reacts with the titanium nitrides; thus, TiO₂ is formed at the outermost titanium nitride layer. The surface hardening was also evaluated by Vickers hardness measurement. The Vickers hardness near the surface of TNTZ and Ti64 increases significantly by gas nitriding.     

钛合金干滑动摩擦行为与磨损机理研究进展

钛合金因具有高的比强度、比刚度,良好的耐蚀性和耐热性等优点,在航空航天、化工、能源等领域广泛应用,但钛合金存在表面硬度低、抗塑性剪切能力较差、不易加工硬化以及表面氧化物保护作用较差等缺陷,使其耐磨性较差,阻碍了其在耐磨损领域的发展。为了提高钛合金自身的耐磨性潜力和扩大其应用领域,本文主要概述了近年来国内外有关钛合金干滑动摩擦磨损领域的研究现状,讨论了影响钛合金摩擦磨损性能的主要因素以及在不同条件下的磨损机理,并对钛合金干滑动摩擦磨损行为的研究进行了展望。     

高强度合金抗疲劳应用技术研究与发展

评述了超高强度钢、高强度Al合金和Ti合金表面完整性抗疲劳应用技术的研究和发展。高强度合金疲劳性能对应力集中敏感，不适当的加工工艺和切削热等造成的表面损伤和高拉应力使其疲劳和应力腐蚀性能损失殆尽。先进的表面完整性加工尤其是表面改性可显著提高疲劳性能，如激光冲击使7475-T761拉-拉疲劳寿命提高约89％，7075-T6裂纹扩展速率降低到原来的1／1500；超声喷丸使超高强度钢低周疲劳强度提高约50％，Ti7Al4Mo合金高周疲劳强度提高约15％；表面超硬化可使Vasco X-2M齿轮钢接触疲劳寿命提高30～35倍等。     

Determining of laser surface treatment parameters used for light metal alloying with ceramic powders

There are presented in this paper the investigation results of microstructure as well hardness investigation of the surface layer of cast aluminium alloys in as‐cast state and after laser surface treatment using a high power diode laser (HPDL) with Al₂O₃ ceramic powder. The purpose of this work was to determine the proper laser treatment conditions for surface treatment of the investigated alloys and to describe the structural changes occurred in the surface layer after laser treatment. For investigation of the obtained structure there was used light as well scanning and transmission electron microscopy. The morphology and size of the ceramic powder particles as well the structure of the remelted aluminium surface layer was possible to determine. After the laser surface treatment carried out on the aluminium cast alloys there are visible structural changes concerning the microstructure as well as distribution and morphology of the fed particles occurred in the sample surface. Concerning the laser treatment conditions for surface hardening also the laser power and ceramic powder feed rate was studied. The structure of the surface laser tray changes in a way, that there are zones detected like the remelting zone and the heat influence zone. This investigation with appliance of a high power diode laser for Al alloys makes it possible to obtain or develop an interesting technology very attractive for different industry branches.     

An Oxygen-Permeation Treatment for Hardening Titanium Alloys

In this paper, the characterization of oxygen permeation (OP) in titanium alloy TC11 at high temperature and the influence of oxygen solution layer on performances of substrate were characterized with the help of apparatus, such as TGA,SEM/EDAX, XRD, EPMA, Micro-hardness Tester, Two-body Abrasion Tester, Amsler Wear Test Machine, Potentiostat/Galvanostat Model 273 system. The results showed that there was a little shift in X-ray diffraction peaks of α and β phase during the OPT process as a result of oxygen solution. The OP treatment can significantly increase the surface hardness of titanium alloys and, accordingly, the abrasive wear resistance was improved. Titanium alloys with oxygen solution layer exhibited improved corrosion resistance both in 3.5 % NaCl and in 5 % HCl solution. Oxidation resistance of TC11 with oxygen solution layer at high temperature was also enhanced. The solution and hardening mechanisms were discussed based on the experimental results.     

Oxygen Diffusion Hardening of Ti-Nb-Zr Alloys

Ti-13Nb-13Zr (Ti-13-13^TM) is a new titanium alloy developed for medical implant applications. In the oxygen diffusion hardened condition, Ti-13-13 and titanium alloys which possess zirconium, are hardenable at temperatures of 400 to 600°C with the end result being a passive, mechanically stable, abrasion resistant oxide ceramic surface layer of about 0.2 to 2 μm in thickness. The thickness of this surface layer depends on the concentration of zirconium, time, temperature, and partial pressure of oxygen. This paper describes the results of x-ray diffraction analysis, secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, Knoop and Nano hardness measurements, and reciprocal polarization resistance measurements of hardened Ti-13-13, and selected Ti-Nb-Zr alloys. The results of this work suggest that zirconium plays a key role for effective oxygen diffusion hardening at 500°C for Ti- ] 3-13 and similar Ti-Nb-Zr alloys.     

高能束技术在镁合金表面改性中的应用

针对如何提高镁合金强度、硬度、耐磨性、耐腐蚀性等综合性能这一热点问题,系统地介绍了激光束、电子束、离子束3种高能束表面改性技术的原理、方法以及在镁合金表面改性中的应用进展,总结了各工艺方法的优缺点,展望了高能束技术在镁合金表面改性中的发展前景。