Al2O3陶瓷爆炸喷涂涂层性能分析

使用爆炸喷涂法制备了Al2O3陶瓷涂层,以自熔性NiAl合金粉末作为底层,基体为45钢。涂层的XRD图谱分析表明,爆炸喷涂的Al2O3陶瓷涂层结构以α-Al2O3及γ-Al2O3为主,说明在爆炸喷涂中存在相变过程;使用国标JB/T7509-94铁试剂方法进行测定,Al2O3陶瓷涂层孔隙率为0.019个/mm2,爆炸喷涂的Al2O3陶瓷涂层结构致密;滑动磨损试验说明,爆炸喷涂Al2O3陶瓷涂层提高了钢基体的耐磨损性能,适用于耐磨涂层。     

原位热压合成Nb掺杂Al2O3/TiAl复合材料

利用Al-Ti-TiO2-Nb2O5体系的放热反应,原位热压合成了Nb掺杂Al2O3/TiAl复合材料.借助DTA结合XRD探讨了Al-Ti-TiO2-Nb2O5体系的反应过程,并采用XRD、OM和SEM研究了复合材料的物相组成及显微结构.结果表明:Al熔化的同时,体系发生了Al和Nb2O5的铝热反应,生成了NbO2和Nb等中间产物,并放出了较多热量,这些热量促使Ti和Al较早化合生成TiAl3,随即引发Al和TiO2较早的还原反应,进而促使材料在较低温度下致密烧结;产物由γ-TiAl、α2-Ti3Al、Al2O3和NbAl3相构成,Al2O3颗粒分布于基体交界处,存在一定的团聚;Nb2O5的引入,对基体γ-TiAl相和α2-Ti3Al相的的分布有一定的影响,使得基体晶粒细化,较好地改善了材料的力学性能.     

激光重熔锌铝基Al2O3陶瓷复合层的组织结构研究

本文研究了激光重熔等离子喷涂锌铝基Al2O3陶瓷复合层的组织结构.结果表明,等离子喷涂Al2O3陶瓷涂层主要由等轴晶状的α-Al2O3陶瓷相组成,长条状的γ-Al2O3陶瓷相量较少,主要分布在α-Al2O3陶瓷相的相界面和几个α-Al2O3陶瓷相晶粒的交汇处;激光重熔后基体相树枝晶得到明显细化,熔池区只存在单一的δ-Al2O3陶瓷相,原α-Al2O3陶瓷相、γ-Al2O3陶瓷相均转变为δ-Al2O3陶瓷相,陶瓷颗粒独立地分布于基体相中,表层陶瓷颗粒数目众多,并有局部富集现象,次表层次之,而在过渡区只能偶尔发现独立存在的陶瓷颗粒.     

发动机用TiAl表面双辉等离子制备W-Mo合金层及其高温氧化行为

目前采用双辉等离子表面合金化技术在TiAl合金表面制备W-Mo涂层的研究不多。通过SEM与XRD等测试手段,研究双辉等离子表面合金化技术在TiAl基体表面制得的W-Mo合金涂层在780℃温度下的氧化行为。研究结果表明:W-Mo改性合金在初期氧化阶段快速氧化增重,经过100 h氧化后,试样增重5.2 mg/cm2,有效改善了TiAl基体的高温抗氧化性能。W-Mo合金涂层对氧气扩散起到阻碍作用,使TiAl基体抗高温氧化性能获得显著提升。氧化处理后合金涂层表面未发生改变,形成了致密、均匀的氧化膜层。TiAl基体经100 h氧化后表面氧化膜主要是一种柱状晶结构,TiAl基体氧化产物包括金红石型TiO2以及刚玉2种成分。     

基于核壳结构粉体设计的CoNiCrAlY-Al2O3复合涂层组织结构及其抗氧化性能

采用核壳结构设计思想,成功将Al2O3包覆于CoNiCrAlY粉体表面制备核壳结构粉末,并通过正交实验设计优化核壳结构粉体的球磨制备工艺;探讨超音速火焰喷涂CoNiCrAlY-Al2O3涂层相结构与微观组织演变规律;对比研究CoNiCrAlY涂层和CoNiCrAlY-Al2O3复合涂层800℃的氧化行为.结果表明:各球磨工艺参数对核壳结构粉末的平均包覆率影响程度从大到小依次为:球磨转速、球料比与球磨时间.制备CoNiCrAlY-Al2O3核壳结构粉末最佳的球磨参数为:球磨转速180 r/min,球料比10:1,球磨时间6 h.超音速火焰喷涂CoNiCrAlY涂层由γ-Co-Ni-Cr相组成.核壳结构粉末中高熔点Al2O3外壳显著抑制了CoNiCrAlY合金在喷涂过程中的氧化行为,导致CoNiCrAlY-Al2O3复合涂层β-NiAl相含量明显增加,涂层孔隙率升高,未熔颗粒增多.由于CoNiCrAlY-Al2O3涂层中的β-NiAl以及Al2O3含量较高,涂层表面在高温氧化过程中形成了致密的富Al2O3的保护层,抑制了非保护性氧化物的生长,使该涂层具有更优异的抗高温氧化性能.     

等离子喷涂Al2O3+13%TiO2陶瓷涂层的组织结构及其耐磨性

本文用X射线衍射、扫描电镜等研究了等离子喷涂Al2O3+13%TiO2(质量分数)陶瓷涂层的相结构、相组成及其组织特征.陶瓷涂层孔隙率低,致密程度较高,以亚稳相γ-Al2O3为主要相,同时存在α-Al2O3和金红石TiO2.富Al2O3区与富TiO2区呈明显相互交迭的层状结构,且存在相互成分扩散.另外,涂层设计对硬度有一定影响,TiO2的引入提高了涂层的耐磨性.     

纯钛材表面电弧喷涂铝层的高温抗氧化性能及机制

为了提高钛材的高温抗氧化性能,采用电弧喷涂方法在纯钛材表面制备了铝涂层,并对其进行800℃,64 h的连续氧化,从铝涂层的微观组织变化,探讨了其高温抗氧化机制。结果表明:电弧喷涂铝涂层可以显著提高纯钛材的高温抗氧化性能;在加热过程中,电弧喷涂的铝涂层发生熔化、扩散,形成了以Al3Ti相为主的扩散层,该富铝相提供充足的铝元素,在涂层表面形成连续的Al2O3,从而对纯钛基体提供有效的高温氧化防护作用。     

纳米陶瓷等离子喷涂层硬度的Weibull分布及与涂层组构的对应特性

等离子喷涂层的硬度是反映其耐磨性、强度、使用寿命的重要指标,它与涂层的组构有对应的关系,但其测定结果分散性较大。为了精确测量陶瓷等离子喷涂层的硬度,在NiCrAl合金表面等离子喷涂制备了Al2O3-13%TiO2(AT13)纳米陶瓷涂层(ncc)和对照用微米涂层(mcc),采用显微硬度测试仪测量了其显微硬度,研究了其Weibull分布特性,通过SEM、XRD等分析了ncc涂层显微硬度与微观组织结构的关系,并通过TEM对涂层的微区结构进行了表征。结果表明:ncc涂层的平均显微硬度显著高于mcc,且呈双态分布;两者硬度的Weibull分布呈分散性,但ncc涂层的分布较均匀,微裂纹细小且粒径小,以α-Al2O3和γ-Al2O3及少量金红石型TiO2为主要物相;ncc涂层具有优异的力学性能主要归因于其组织的晶粒细化、纳米TiO2颗粒镶嵌于Al2O3孔隙中、Al2O3微晶弥散分布、微裂纹韧化等。     

Hf对Pt改性γ’-Ni3Al单相磁控溅射层氧化行为的影响

γ＇-Ni3Al高温合金表面溅射纳米晶涂层和铂改性γ＇＋γ＇涂层的成分、结构与基体相近,涂层脆性、相容性等改善明显,但有关改性层抗高温氧化性的研究有待深入。通过磁控溅射方法在γ＇-Ni3Al基高温合金表面沉积Ni3（Al,Hf）纳米晶涂层,在溅射层表面电镀1．5μm的Pt,1150℃扩散退火1h,得到Pt＋Hf改性的γ＇-Ni3Al单相涂层,不含Hf的涂层中没有明显的浓度梯度,而含Hf涂层中则有明显的浓度梯度。通过场发射扫描电镜（EFG—SEM）、X射线衍射（XRD）、电子探针（EPMA）和能谱（EDX）分析了涂层的结构与成分,考察了Pt改性γ＇-Ni3Al单相涂层在l050oC下空气中的氧化行为。结果表明：不合Hf的涂层生成外层为NiAl2O4、内层为Al2O3的复合氧化膜,含Hf的涂层均生成单一的Al2O3膜,Hf促进了Al的选择性氧化。适当含量的Hf降低了Pt改性γ＇-Ni3Al涂层的氧化速率,但是过高含量的Hf则使得涂层的氧化速率升高。     

TiAl合金表面激光重熔等离子喷涂MCrAlY涂层研究

为了进一步提高TiAl合金表面等离子喷涂MCrAlY涂层的高温氧化性能,采用激光重熔工艺对涂层进行处理,研究了激光重熔对涂层微观组织及抗氧化性能的影响.用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析了涂层氧化前后的表面形貌、微观组织和相组成.结果表明:经过激光重熔处理后,涂层片层状组织得以消失,致密性提高,消除了喷涂层的大部分孔洞、夹杂等缺陷,同时使Al元素在涂层表面的重新分布,形成了Al的富集区;等离子喷涂MCrAlY层能显著提高TiAl合金的抗高温氧化性能,经过激光重熔后可进一步提高其抗高温氧化性能.     

钛合金表面梯度Al2O3陶瓷涂层的高温抗氧化性能

钛合金应用广泛,但在高温环境中极易被氧化,降低其力学性能及寿命。利用溶胶-凝胶法在TC11钛合金上制备梯度层(ZrO_2+Al_2O_3)+表层(Al_2O_3)的复合梯度涂层,提高其高温抗氧化能力。将复合梯度涂层、单层氧化铝涂层以及基体在700℃进行100h的高温氧化,利用氧化增重数据拟合得到梯度涂层的氧化速率为0.015mg~2/(cm4·h),氧化指数为2.137,并结合氧化后EDS成分分布,发现复合梯度涂层可以提高基体的高温抗氧化性能。同时利用700℃热震实验比较了复合梯度氧化铝涂层试样和单层氧化铝陶瓷试样的热震次数,梯度层(ZrO2+Al_2O_3)的存在缓解了基体与氧化铝陶瓷涂层之间热膨胀系数不匹配而导致的易剥落的问题,延长了涂层寿命,进一步提高了基体的高温抗氧化能力。     

TiAl合金表面Si-Al-Y共渗层的组织及高温抗氧化性能

通过在1050℃下Si-Al-Y扩散共渗0~4 h在TiAl合金表面制备了Al、Y改性的硅化物抗氧化渗层, 分析了共渗层的结构及相组成, 并对其组织形成机理及高温抗氧化性能进行了研究。结果表明: 1050℃共渗4 h所制备的共渗层具有多层结构, 由外向内依次为TiSi₂外层、(Ti,X)₅Si₄及(Ti,X)₅Si₃(X表示Nb, Cr)中间层、TiAl₂和γ-TiAl内层及富Al的过渡层, 其中Y元素主要富集于共渗层的外层和中间层。不同时间共渗的结果表明, Si-Al-Y共渗层的形成是一个在基体表面先沉积Al, 后沉积Si的有序过程。经1000℃高温氧化20 h后共渗层表面形成了由TiO₂外层及SiO₂·Al₂O₃次外层组成的致密氧化膜; Y的氧化物主要存在于氧化膜与残余共渗层的界面处, 能够有效地增强膜层的附着力。     

高温氧化对钛合金微弧氧化陶瓷膜组成与结构的影响

针对钛合金不耐高温氧化的问题,在铝酸钠电解液体系中,利用双相脉冲直流微弧氧化技术,在TC4钛合金表面原位生长以Al2TiO5为主晶相的复合氧化物陶瓷膜,研究了1000℃高温氧化对陶瓷膜试样的相组成、结构的影响及膜层增重特点.研究表明,陶瓷膜层试样的高温氧化过程包括Al2TiO5分解、基体氧化和膜层表面形貌变化3个方面.高温氧化后,膜层的主晶相由Al2TiO5变为α-Al2O3和金红石型TiO2,同时,膜层的表面形貌发生显著的变化;由于膜层和基体的热膨胀系数不同和基体钛的氧化,使得高温氧化后膜层在冷却过程中表面出现裂纹和脱壳.陶瓷膜层极大地减少了TC4钛合金在1000℃高温氧化时的增重,因此,陶瓷膜层可用于TC4钛合金的恒温氧化防护.     

In vitro evaluation of human osteoblast adhesion to a thermally oxidized γ-TiAl intermetallic alloy of composition Ti–48Al–2Cr–2Nb (at.%)

Ti–48Al–2Cr–2Nb (at.%) (γ-TiAl), a gamma titanium aluminide alloy originally designed for aerospace applications, appears to have excellent potential as implant material. Thermal treatment of γ-TiAl renders this alloy extremely corrosion resistant in vitro, which could improve its biocompatibility. In this study, the surface oxides produced by thermal oxidation (at 500°C, and at 800°C for 1 h in air) on γ-TiAl were characterized by X-ray photoelectron spectroscopy (XPS). hFOB 1.19 cell adhesion on thermally oxidized γ-TiAl was examined in vitro by a hexosaminidase assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) after 1, 7 and 14 days. Ti–6Al–4V surfaces were used for comparison. Hexosaminidase assay data and CLSM analysis of focal contacts and cytoskeleton organization showed no differences in cell attachment on autoclaved and both heat-treated γ-TiAl surfaces at the different time points. SEM images showed well organized multi-layers of differentiated cells adhered on thermally oxidized γ-TiAl surfaces at day 14. Unexpectedly, thermally oxidized Ti–6Al–4V surfaces oxidized at 800°C exhibited cytotoxic effects on hFOB 1.19 cells. Our results indicate that thermal oxidation of γ-TiAl seems to be a promising method to generate highly corrosion resistant and biocompatible surfaces for implant applications.     

Oxidation protective coatings for γ‐TiAl – recent trends

Engine designers show continued interest in γ‐TiAl based titanium aluminides as light–weight structural materials to be used at moderately elevated temperatures. Although alloy development has made significant progress in terms of mechanical properties and environmental resistance, protective coatings have been developed that help to extend the lifetime of these alloys significantly. The major challenge of coating development is to prevent the formation of fast growing titania. Furthermore, changes of coating chemistries at high temperatures have to be considered in order to avoid rapid degradation of the coatings due to interdiffusion between substrate and coating. The paper describes recent work of the authors on different coatings produced by means of magnetron sputter technique. Thin ceramic Ti‐Al‐Cr‐Y‐N layers tested at 900 °C exhibited poor oxidation resistance. In contrast, intermetallic Ti‐Al‐Cr, Si‐based and aluminum rich Ti‐Al coatings were tested at exposure temperatures up to 950 °C for 1000h resulting in reasonable and partially excellent oxidation behaviour.     

Oxidation Behavior of Pd-Modified Aluminide Coating at High Temperature

(Ni,Pd)Al coating, prepared by low pressure pack cementation on the Ni-base superalloy M38 where Pd-20 wt pct Ni alloy was predeposited, consists of a single β-(Ni,Pd)Al phase. The initial isothermal oxidation behavior of (Ni,Pd)Al coating was investigated by TGA, XRD, SEM/EDS at 800～1100℃. Results show that oxidation kinetics accord preferably with parabolic law at 800, 900 and 1100℃, but not at 1000℃.θ-Al2O3 was observed at 800～1100℃. It is found that Pd plays an important role in accelerating the diffusion of Ti from the substrate to the coating surface in the aluminide coating.     

2024铝合金微弧氧化涂层的耐磨性能

为了提高2024铝合金的耐磨性,对其进行微弧氧化。利用扫描电镜(SEM)和X射线衍射仪(XRD)分析了涂层的微观组织结构和物相组成;采用高速往复摩擦磨损试验机对2024铝合金微弧氧化涂层在不同载荷下的磨损性能进行了研究,并采用白光三维形貌仪进行磨损形貌分析及磨损体积计算。结果表明:2024铝合金微弧氧化涂层是一种微孔结构,涂层相主要成分为α-Al_2O_3、γ-Al_2O_3,且Al_2O_3具有高硬度、耐磨损的优良特性,有利于提高铝合金的耐磨损性能;微弧氧化涂层的摩擦系数随着载荷的增加而减小,而磨损量随载荷的增加而增加,磨损机理为磨粒磨损。     

Fabrication of (TiB/Ti)-TiAl composites with a controlled laminated architecture and enhanced mechanical properties

The(TiB/Ti)-TiAl composites with a laminated structure composing of alternating TiB/Ti composite layers,α₂-Ti₃Al interfacial reaction layers of andγ-TiAl layers were successfully pre pared by spark plasma sintering of alternately stacked Tib₂/Ti powder layers and TiAl powder layers.And the influence of thickness ratio of Tib₂/Ti powder layers to TiAl powder layers on microstructure evolution and mechanical properties of the re sulting(TiB/Ti)-TiAl laminated composites were investigated systemically.The results showed that the thickening ofα₂-Ti₃Al layers which originated from the reaction of Ti and TiAl was significantly hindered by introducing Tib₂particles into starting Ti powders.As the thickness ratio of Tib₂/Ti powder layers to TiAl powder layers increased,the bending fracture strength and fracture toughness at room temperature of the final(TiB/Ti)-TiAl laminated composites were remarkably improved,especially for the(TiB/Ti)-TiAl composites prepared by Tib₂/Ti powder layers with thickness of 800μm and TiAl powder layers with thickness of 400μm,whose fracture toughness and bending strength were up to 51.2 MPa·m^1/2and 1456 MPa,respectively,293%and 108%higher than that of the monolithic TiAl alloys in the present work.This was attributed to the addition of high-performance network TiB/Ti composite layers.Moreover,it was noteworthy that the ultimate tensile strength at 700℃of(TiB/Ti)-TiAl composites fabricated by 400μm thick Tib₂/Ti powder layers and 400μm thick TiAl powder layers was as high as that at 550℃of network TiB/Ti composites.This means the service temperature of(TiB/Ti)-TiAl laminated composites was likely raised by 150℃,meanwhile a good combination of high strength and high toughness at ambient tempe rature could be maintained.Finally,the fracture mechanism of(TiB/Ti)-TiAl laminated composites was proposed.     

钛材用铝基耐高温涂层的防氧化性能研究

通过制备一种钛材铝基耐高温防氧化涂层以防止铸锭开坯过程中由于高温加热所造成的钛的损失以及氧化引起的表面缺陷,进而保护钛材;研究了涂层厚度和加热时间对涂层防氧化性能的影响。结果表明:由于该氧化保护涂层的主要组成是片状的金属铝粉末,一方面铝在加热过程中会与空气中的氧反应生成致密氧化层Al2O3,可有效地阻止氧的渗透;另一方面在高温加热过程中,铝和钛及钛合金可以发生反应,生成具有优良抗氧化性的TixAly相,能有效阻止钛的硬氧化层的形成从而起到保护基体的作用。在1 050℃恒温8 h条件下,涂层厚度在50150μm之间变化对涂层的抗氧化性能没有影响,随加热时间延长至16 h时,其抗氧化能力减弱。     

Fe-5Cr合金表面溶胶-凝胶复合涂层的抗高温腐蚀性能研究

在含氧化铝-氧化钇纳米粒子的胶体中添加氧化铝的微米粒子,借助高能球磨机研磨,将纳米或微米陶瓷粉末均匀地分散在溶胶-凝胶溶液中形成涂覆液;采用浸渍提拉法将溶胶-凝胶涂覆液沉积在Fe-5Cr合金基体表面上,然后通过烧结得到厚的陶瓷涂层。利用SEM及EDS对涂层进行了结构、成分以及表面形貌的分析,用XRD技术对涂层表面的相组成进行了分析。采用氧化增重法研究了Fe-5Cr合金基体材料及其涂层的抗高温氧化及硫化性能。研究结果表明,带有溶胶-凝胶复合涂层的试样在600℃下具有优异的抗高温氧化及较好的抗高温硫化性能。