Ti-6 Al-4 V 表面等离子渗锆及锆合金层的性能

目的通过等离子表面合金化渗锆,提高Ti-6Al-4V的表面硬度及在还原性酸中的耐蚀性能。方法分别在800,850,900℃渗锆,分析研究锆合金层的成分、相组成、显微硬度及在为10%(质量分数)H2SO4溶液中的腐蚀行为,并与未处理的基材进行对比。结果 Ti-6Al-4V在三种温度下渗锆后,形成的表面合金层主要由锆在α-Ti或β-Ti中形成的固溶体组成,元素组成呈梯度分布,表面粗糙度随渗锆温度的提高而增加,硬度由表及里呈梯度下降,表面硬度比未处理的Ti-6Al-4V提高了约200HV0.1。与未处理的基材相比,Ti-6Al-4V渗锆后,在10%H2SO4溶液中的自腐蚀电位均正移,钝化电流密度均有所减小。结论 Ti-6Al-4V渗锆后,硬度和耐蚀性较基体有所提高,其中,900℃渗锆后的耐蚀性最好,800℃与850℃渗锆试样的耐蚀性次之。     

双辉技术渗铌对Ti-6Al-4V合金氧化性能的影响

采用双辉等离子渗金属技术在Ti-6Al-4V表面形成均匀致密连续的渗铌合金层。将未渗铌和渗铌的Ti-6Al-4V试样分别在700℃，800℃，900℃进行100h的高温氧化实验，采用XRD，SEM及EDX对试样在900℃氧化100h后的氧化层的相组成、截面形貌及成分分布进行分析，初步探讨Ti-6Al-4V表面渗铌后的抗氧化性能及氧化机理。结果表明：渗铌后的Ti-6Al-4V合金氧化速率常数降低了1个数量级，氧化激活能提高，抗氧化性能明显改善。     

离心研磨工艺对Ti-6 Al-4 V钛合金表面组织性能的影响

目的改善Ti-6Al-4V钛合金的组织性能。方法使用离心研磨工艺对Ti-6Al-4V钛合金进行表面处理,通过显微硬度计、X射线应力分析仪、金相显微镜,对不同加工时间下试样表层的显微硬度、残余应力、金相组织进行测试。结果离心研磨加工后,Ti-6Al-4V钛合金表面的显微硬度得到提高,试样最表面的显微硬度随加工时间的延长呈现逐渐增大的趋势,加工时间为40 min时,显微硬度达到最大值385HV,比试样基体硬度值提高了55HV;在加工深度方向上,随着深度的增加,显微硬度值逐渐降低,在深度为400μm附近,显微硬度值已与基体硬度值相差不大,并且基本不再下降。加工完成后,试样表面产生了有益的残余压应力,最大残余压应力值为436 MPa。金相组织分析结果表明,试样表层组织形成了剧烈塑性变形层,其深度约40μm,在变形层内,组织的晶粒得到明显细化。结论离心研磨抛光工艺对Ti-6Al-4V钛合金表面组织性能改善效果明显,验证了使用该工艺对Ti-6Al-4V钛合金进行表面强化的可行性。     

渗氮-渗硫复合处理对Ti-6Al-4V合金摩擦学性能的影响

采用离子渗氮-渗硫复合处理在Ti-6Al-4V合金的表面形成复合渗层.用X射线衍射仪和扫描电子显微镜对复合渗层的相结构和渗层表面微观形貌进行了分析;并对复合渗层的摩擦学性能进行测试.结果表明,渗氮-渗硫复合处理,可在Ti-6Al-4V合金的表面形成具有良好减摩作用的硫化物层、次表层为具有高硬度的氮化物层和过渡层的理想的摩擦学表面.与未渗硫处理的试样相比,摩擦系数显著降低.     

用热扩散方法在Ti-6Al-4V合金表面获得铝化物和硅化物涂层

采用固体粉末包装热扩散方法,对Ti-6Al-4V合金分别进行表面渗铝和渗硅处理,以提高该合金的抗高温氧化性能。结果表明:Ti-6Al-4V合金表面形成的铝化物涂层的金相组织为单层结构,其上有少量贯穿裂纹存在;主要相结构是TiAl_3。而硅化物涂层的金相组织则为双层结构,外层较厚,呈柱状晶,由TiSi_2相组成;内层则较薄,由Ti_5Si_4相组成。表面渗铝和渗硅处理都可以大大提高Ti-6Al-4V合金的抗高温氧化性能。     

钛合金辉光离子渗硫与摩擦学特性研究

对Ti-6Al-4V合金表面进行辉光离子渗硫处理后的显微组织、摩擦学特性进行了研究.结果表明:合金经离子渗硫处理后,渗层主要由TiS2、TiS、TiS3、Ti2S等硫化物组成;对处理前后试样的摩擦学性能研究显示,渗硫后试样在干摩擦纯滑动的情况下表现出良好的减摩性能,并对减摩机理进行了探讨.     

铸造Ti-6Al-4V钛合金流动性研究

制备石墨型和陶瓷型两种铸型,浇注螺旋形试样,考查了Ti-6Al-4V钛合金的流动性。在真空凝壳炉下重熔Ti-6Al-4V合金,浇注流动性试样并测量其流动长度,比较两种铸型下Ti-6Al-4V以及陶瓷型下Ti-6Al-4V不同Fe含量时的流动性能。结果表明,铸型材料对合金流动性影响较大,陶瓷型流动长度高于石墨型近2倍,陶瓷型条件下Ti-6Al-4V合金流动性随Fe含量增加而略有下降,0.25%的Fe含量时流动长度约为0.05%的Fe时的80%。     

Ti-6Al-4V钛合金的等离子W-Mo共渗

采用双层辉光等离子表面合金化技术对Ti-6Al-4V钛合金进行W-Mo共渗,研究了880～1000 ℃ W-Mo共渗时基体温度对渗层厚度的影响,采用SEM和XRD观察、检测渗层组织结构和相组成.结果显示,Ti-6Al-4V合金的W-Mo渗层组织良好.纳米压痕试验结果表明,合金渗层硬度高于基体.     

表面纳米化预处理对Ti-6Al-4V合金渗硼的影响

研究了表面纳米化预处理对Ti-6Al-4V合金渗硼的影响。采用表面机械研磨处理(SMAT)在Ti-6Al-4V合金表面预先制备出一层纳米晶层,随后采用粉末渗硼法对纳米晶样品进行渗硼处理,并利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和微观硬度测试仪等对渗硼层的相组成、结构形貌、显微硬度和韧性进行了表征与测试。结果表明:表面纳米化预处理可以显著增强Ti-6Al-4V合金低温渗硼动力学,降低渗硼温度。与未处理的高温渗硼样品相比,纳米化预处理样品低温渗硼层硬度和耐磨性略有下降,但仍满足工业应用要求。渗层脆性级别评定表明表面纳米化预处理可以有效降低渗硼层的脆性。     

Ti-6Al-4V合金表面等离子Nb合金化工艺

采用双辉等离子表面冶金技术对Ti-6Al-4V合金进行等离子渗铌处理。研究了温度与保温时间对合金层元素含量和渗层厚度的影响,以确定最佳渗金属工艺参数。利用光学图像分析仪以及辉光放电能谱仪观察和测定合金层的金相组织、渗层厚度及成分。结果表明,在极间距和气压恒定的条件下,渗层厚度及成分与温度和保温时间有关。温度过高或保温时间过长均会在Ti-6Al-4V试样表面产生较厚的Nb沉积层。经优化工艺参数,选择850℃保温3 h渗铌,得到一定厚度且与基体为冶金结合的合金层。该合金层可以克服Ti-6Al-4V合金耐磨性差的缺点。     

Ti-6Al-4V钛合金固体渗硼法表面改性

对TC4钛合金(Ti-6Al-4V)进行表面渗硼使其表面硬度显著提高.渗硼温度为1000℃到1050℃,渗硼时间为5 h到20h.文内测量和比较了渗硼后钛合金表面的微结构、形貌、相组成等性质,研究了渗硼过程中Ti,Al,V,B等元素的扩散行为.在低温短时间渗硼时,渗硼层厚度仅0.8μm,而在高温长时间渗硼时,渗硼层厚度可达15 μm.实验证明,渗硼层由TiB和TiB2两相组成,并且它们的含量随渗硼温度提高而增加.渗硼层表面主要含TiB2,其显微硬度可达2200 HV0.01,渗硼层内表层主要含TiB,其显微硬度为1100 HV0.01.渗硼层的硬度远高于TC4钛合金的硬度.     

Microstructure and Cavitation Erosion Properties of Ceramic Coatings Fabricated on Ti-6Al-4V Alloy by Pack Carburizing

In this study, Ti-6Al-4V alloy was processed by pack carburizing to improve the cavitation erosion behavior. X-ray diffraction and scanning-electron microscopy (SEM) analysis showed that a uniform and crack-free ceramic coating formed on the surface of the treated samples. The coating layer comprised primary TiC and less oxide. Cavitation erosion experiment results indicated that the treated samples have the factor of 3.44 to 6.68 increase in cavitation erosion resistance (R _e) as compared with the as-received sample. The ceramic coatings with high hardness and good metallurgical bonding were responsible for the enhanced cavitation erosion properties. When the coatings were treated at condition of high temperature and/or long time, the R _e was enervated due to the thin oxide film formed at the outermost surface. Cavitation erosion mechanism for the coatings was characterized as brittle mode by SEM observation of the worn surfaces.     

近β钛合金表面包覆渗氧强化

利用一种钛合金表面防护涂料对近β钛合金Ti-1023进行表面包覆后,在不同温度和气氛环境下进行高温渗氧强化处理。对渗氧处理后的合金表层显微组织和硬度梯度进行表征。结果表明,涂层包覆可以有效减缓Ti-1023合金的高温氧化行为,抑制表面疏松的脆性氧化物的形成,提高合金表面硬度。在空气气氛下,经850 ℃×24 h渗氧处理后Ti-1023合金表层显微硬度由321 HV0.2提高到544 HV0.2,硬化深度达500 μm以上。在T_β以下750 ℃氧气气氛中渗氧48 h后,合金表层显微硬度可达459 HV0.2,并且合金基体组织基本不受影响。     

Comparison of molybdenizing and NiCrA1Y coating on Ti and Ti-6A1-4V

Two surface treatments, molybdenizing and depositing NiCrAIY coating, were applied to improve the microhardness and the oxidation re-sistance of titanium and Ti-6Al-4V. Coupons were analyzed using optical microscopy (OM), scanning electron microscopy (SEM) with X-ray energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). Vickers hardness and isothermal oxidation tests were carded out to evaluate the effects of these two surface treatments on the microhardness and oxidation resistance of the substrates. The post vacuum heat treatment of the NiCrAlY coating and the molybdenizing parameters were also discussed. It is found that molybdenizing can obviously in-crease the surface hardness of titanium due to the formation of β,α", and α' phases in the diffusion layer. As γ' phase is formed after vacuum heat treatment, the NiCrAIY coating is effective in improving the surface hardness of Ti-6Al-4V. The NiCrAlY coating can obviously de-crease the oxidation rate of Ti-6Al-4V at 700-900℃, which can be attributed to the formation of Al2O3 and Cr2O3 mixed scale during the oxidation.     

钛合金空蚀损伤及防护的研究进展

钛合金具有密度小、比强度高、耐蚀性好等优势,被广泛应用于诸多工程领域。由于钛合金存在表面硬度低、耐磨性差等缺点,导致其在过流部件中容易发生空蚀损伤,会降低钛合金构件的使用寿命,因此针对钛合金空蚀损伤行为及其防护措施的研究显得极为重要。概述了空蚀现象的作用机理和理论模型,详细介绍了材料自身的力学性能、表面状态、介质类型和溶液温度等对钛合金空蚀行为的影响,着重讨论了针对钛合金空蚀损伤的多种应对措施,如热处理、激光纹理加工、激光气体氮化、化学热处理、离子注入、添加缓蚀剂等技术,总结了相应方法提高钛合金抗空蚀性能的具体原因。其中,热处理技术通过改变钛合金自身的显微组织来提高其抗空蚀性能;激光气体氮化工艺可在钛合金表面形成硬质TiN相,以抵御空泡溃灭时的冲击;化学热处理技术在钛合金表面生成了致密的陶瓷层+固溶扩散层,缓解了空泡的溃灭能,延长了空蚀的孕育期;离子注入技术依靠注入离子在钛合金材料表面产生固溶强化、位错增值强化等效果,降低其空蚀损伤。最后对钛合金空蚀及防护研究的发展方向提出了展望。     

Comparison of molybdenizing and NiCrAlY coating on Ti and Ti-6Al-4V

Two surface treatments, molybdenizing and depositing NiCrAlY coating, were applied to improve the microhardness and the oxidation resistance of titanium and Ti-6Al-4V. Coupons were analyzed using optical microscopy (OM), scanning electron microscopy (SEM) with X-ray energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). Vickers hardness and isothermal oxidation tests were carried out to evaluate the effects of these two surface treatments on the microhardness and oxidation resistance of the substrates. The post vacuum heat treatment of the NiCrAlY coating and the molybdenizing parameters were also discussed. It is found that molybdenizing can obviously increase the surface hardness of titanium due to the formation of β, α″, and α′ phases in the diffusion layer. As γ′ phase is formed after vacuum heat treatment, the NiCrAlY coating is effective in improving the surface hardness of Ti-6Al-4V. The NiCrAlY coating can obviously decrease the oxidation rate of Ti-6Al-4V at 700–900°C, which can be attributed to the formation of Al₂O₃ and Cr₂O₃ mixed scale during the oxidation.     

Ti-6Al-4V合金表面激光熔覆TiAlSi+xB4C涂层的组织及耐磨性

利用激光熔覆在Ti-6Al-4V合金表面制备了TiAlSi+xB₄C涂层,分析比较不同B₄C含量对于涂层显微组织、显微硬度和耐磨性能的影响。结果表明:B₄C含量不同,涂层中的物相种类差别不大;涂层的微观形貌由颗粒状晶、层状晶、胞状晶和短棒状晶组成;不同B₄C含量涂层的显微硬度分布趋势大致相同,与基材相比均有明显的提高,随着B₄C含量的增高,整体上涂层显微硬度逐渐增大,当B₄C的含量为8%时,涂层的显微硬度最高,达到1216 HV0.1,约为基体的4.2倍;而当B₄C含量过高时,涂层硬度降低,且涂层中出现微裂纹。通过磨损试验表明,不同B₄C含量的涂层耐磨损性能均明显的优于Ti-6Al-4V合金基体,含8%B₄C的涂层磨损量最小。熔覆不同含量B₄C的涂层明显改善了基体Ti-6Al-4V合金的表面性能。     

Corrosion resistance properties of plasma nitrided Ti-6Al-4V alloy in nitric acid solutions

The corrosion resistance of plasma nitrided Ti-6Al-4V titanium alloy in nitric acid solutions was investigated using polarisation curves, cyclic voltammetry, XRD analysis and surface microhardness. For comparison, untreated alloy samples were tested under the same conditions. While the untreated alloy shows a passive behaviour, the compound layer obtained by glow-discharge nitriding treatment, which is composed of an outer TiN and an inner Ti₂N layer, shows a high electrochemical inertia; however, if the polarisation potential is higher than a threshold or the period of immersion in high oxidising acid solution is sufficiently long, then the compound surface layer will be attacked and removed with corrosion rate higher than in the case of the untreated Ti-6Al-4V alloy. The corrosion resistance of Ti₂N layer results higher in comparison with that of TiN layer.     

Ti3Al基合金的弹性变形能与空蚀

利用旋转圆盘装置研究了Ti3Al基合金Ti-24A1-15Nb-1Mo的空蚀行为，并用洛氏硬度仪模拟空蚀过程中微射流所产生的局部载荷对Ti-24A1-15Nb-1Mo合金的作用，测量了压头加载过程中该合金吸收的总能量和弹性变形能(选择我国水利机械常用0Cr13Ni5Mo马氏体不锈钢作对比材料)。结果表明：Ti-24Al-15Nb-1Mo合金的抗空蚀性能优于0Cr13Ni5Mo不锈钢，空蚀40h后前者的累积体积损失量仅为0．551mm^3，而后者的累积体积损失量达到2．615mm^3；在局部载荷作用下，Ti-24Al-15Nb-1Mo合金不仅有较高的加工硬化能力，而且有较好的弹性性能；在压痕试验中其弹性变形能在总变形能量中所占比例达到1／3。这些性能特点使Ti-24Al-15Nb-1Mo合金在空蚀过程中能吸收和释放较多的冲击能量，延缓裂纹形成，减少体积损失，呈现良好的抗空蚀性能。