Interface characteristics of Al_2O_3－13%TiO_2 ceramic coatings prepared by laser cladding

Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating： one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.

Effects of Yttrium Ion on Formation Mechanism of ZrO_2-Y_2O_3 Ceramic Coatings Formed by Plasma Electrolytic Oxidation on Al-12Si Alloy

ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that adding an appropriate amount of yttrium ion can improve the growing rate of ceramic coating at different oxidation stages and decrease arc voltage. The thickness of ZrO2-Y2O3 coating is 16 μn thicker than that of ZrO2 coating and the maximum oxidation rate improves by 0.6 μm/min. In addition, the arc voltage decreases from 227 to 172 V. It can be seen that the rate of oxidation firstly increases to some extent and then decreases with the content of yttrium ion increasing. The growth rate reaches the maximum while the content of yttrium ion is 0.05 g-L-1The maximum thickness is 90 μm.Compared to ZrO2 coating, the micropores of ZrO2-Y2O3 coating are less and the ceramic layer is repeatedly deposited by ZrO2 and Y2O3 ceramic particles. Meanwhile, the binding force between coating and substrate is better and the coating is uniform and compact. The ceramic layer is mainly composed of c-Y0.15Zr0.85O1.93□0.07, m-ZrO2, α-Al2O3, ,γ-Al2O3 and Y2O3. It is indicated that ZrO2 has beert fully stabilized by yttrium ion through the formation of solid solution.

Corrosion Resistance of Ceramic Coating on Steel Substrate

Fe/Al2O3 ceramic coating was made by spraying and sol-gel. The corrosion resistance between Fe/Al2O3 ceramic coating and steel 45# was studied. By microscope and X-ray diffraction, the binding and the composition of the interface were also analyzed. The results showed that Fe/Al2O3 ceramic coating had dense struc- ture, less porosity and better binding with the substrate which was effective to prevent erosive liquor immersing into the inside of ceramic coating. Some substances that distributed homogeneously in Fe/Al2O3 ceramic coating, such as α-Al2O3, FeAlO3 and Fe3Al, could improve the corrosion resistance of this material.

Structural characteristics and high-temperature tribological behaviors of laser cladded NiCoCrAlY−B_(4)C composite coatings on Ti6Al4V alloy

In order to improve the hardness and tribological performance of Ti6Al4V alloy,NiCoCrAlY-B_(4)C composite coatings with B_(4)C of 5%,10%and 15%(mass fraction)were fabricated on its surface by laser cladding(LC).The morphologies,chemical compositions and phases of obtained coatings were analyzed using scanning electronic microscope(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD),respectively.The effects of B_(4)C mass fraction on the coefficient of friction(COF)and wear rate of NiCoCrAlY-B_(4)C coatings were investigated using a ball-on-disc wear tester.The results show that the NiCoCrAlY-B_(4)C coatings with different B_(4)C mass fractions are mainly composed of NiTi,NiTi_(2),α-Ti,CoO,AlB_(2),TiC,TiB and TiB_(2)phases.The COFs and wear rates of NiCoCrAlY-B_(4)C coatings decrease with the increase of B_(4)C content,which are contributed to the improvement of coating hardness by the B_(4)C addition.The wear mechanisms of NiCoCrAlY-B_(4)C coatings are changed from adhesive wear and oxidation wear to fatigue wear with the increase of B_(4)C content.

Effect of Al_2O_3on Structure and Wearability of Composite Coating

The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influences of contents and sizes of AlOon the structure and wearability were investigated.The results show that the wear resistance of the coating would be increased greatly by adding AlO,but the spray weldability decreases with increasing AlOcontent.So there is an optimal content of AlOpowder.The composite coating with AlOnano or sub-micron powder of 0.5% has the best abrasive resistance,while the optimal content of AlOmicron powder is 1 %.

Microstructural Characteristics and Wear Performance of Plasma Sprayed Al_2O_3-13 wt. % TiO_2 Coating on the Surface of Extrusion Wheel

The conventional Al2O3-13 wt. % TiO2 composite ceramic coatings are fabricated by plasma spraying on the surface of extrusion wheel. The microstrueture, morphology and phase compositions of the substrate and coat- ing are investigated by using X-ray diffractometry （XRD） , scanning electron microsopy （SEM） and energy dis- persive spectroscopy （EDS）. Moreover, the microhardness of the substrate and the coating are investigated using Vickers mierohardness tester, the friction and wear behaviors of the substrate and the coating are investigated by using a block-on-ring tribometer under dry sliding conditions with the load of 245 N. The results show that both γ-Al2O3 and α-Al2O3 phases are observed in the as-sprayed coatings, the mian phase is γ-Al2O3. There are white particulates Al2O3 on its surface. The Al2O3-13 wt. % TiO2 coating possesses higher mierohardness which is about 1018HV and 1.6 times that of the substrate. The wear performance of coating is better than that of the substrate. In a practical application, the life of the extrusion wheel which is plasma sprayed Al2O3-13 wt. % TiO2 coating on the surface is 1.2 times that of the conventional extrusion wheel, and the life is about 330 h.

镀铝对CoCrNiAlY-YSZ-LaMgAl_(11)O_(19)双陶瓷热障涂层高温抗氧化行为的影响

采用电弧离子镀(AIP)技术在CoCrNiAlY-YSZ-LaMA双陶瓷涂层表面沉积一层Al镀层,利用XRD、SEM和EDS等微尺度分析表征方法,全面解析涂层在大气暴露过程中的高温氧化行为。研究结果表明,未镀铝LaMA层在氧化过程中发生严重体积收缩,导致纵向微裂纹萌生和扩展。这些微裂纹成为氧气向内部扩散的通道,导致涂层呈现持续氧化增重趋势、TGO快速生长和严重的元素扩散,并最终加剧涂层断裂失效。但镀铝涂层样品表现出更好的高温抗氧化性能与结构稳定性,高温氧化过程中,表面Al镀层与氧气发生原位反应生成致密Al2O3屏障层,有效阻止或延迟氧气内部渗透,使TGO缓慢生长,其氧化增重从20h时的8.59mg/cm^(2)略微上升到80h时的9.46mg/cm^(2)。本研究结果为双陶瓷热障涂层的延寿设计与界面热生长应力调控开辟出全新技术途径和理论视野。

碳/碳复合材料SiC/Al-Si涂层微观结构及抗氧化性能研究

采用料浆法在碳/碳复合材料碳化硅(SiC)内涂层表面制备了Al-Si合金外涂层,采用XRD和SEM分析了涂层的微观结构,并测试了带有SiC/Al-Si复合涂层的碳/碳复合材料试样在1500℃静态空气中的抗氧化性能。结果表明:Al-Si合金外涂层主要成分为Al3.21Si0.47,含有少量Al2O3;SiC/Al-Si复合涂层厚度约为120μm,无穿透性裂纹;SiC/Al-Si复合涂层的抗氧化性能明显优于单一SiC涂层,氧化17h后涂层试样的质量损失未超过5%。

C/Al复合材料中镍涂层的界面行为

为改善纤维与基体的润湿性,在碳纤维表面涂覆Ni、SiC-Ni。经铝液浸渗实验表明Ni涂层可以使纤维很好地分布于基体中。但Ni单涂层导致碳纤维损伤,Ni、SiC-Ni两状态下界面与基体中均产生大量脆性相,急剧降低复合材料的强度。

SiC晶须和Ti(C,N)颗粒协同增韧Al_2O_3陶瓷刀具的研究

采用热压工艺烧结制备了SiCW Ti(C ,N) Al2 O3(Y2 O3)陶瓷刀具复合材料。研究了不同烧结温度(16 0 0～ 175 0℃ )下 ,材料的致密度和力学性能 (断裂韧性KIC ,维氏硬度HV和抗弯强度σf)随晶须含量 (10 %～4 0 % )的变化关系 ;探讨了SiC晶须和Ti(C ,N)颗粒对Al2 O3基体的协同增韧机理。同时与SiCW Al2 O3陶瓷及Ti(C ,N) Al2 O3陶瓷作对比研究。结果表明 :SiCW Ti(C ,N) Al2 O3(Y2 O3)陶瓷材料在 175 0℃ ,晶须含量为 2 0 %时获得最佳的综合力学性能 :KIC =7 11MPa m1 2 ,HV =2 1 16GPa ,σf=82 0MPa ;明显高于SiCW 含量为 2 0 %的SiCW Al2 O3陶瓷和不加晶须的Ti(C ,N) Al2 O3陶瓷。第三相Ti(C ,N)颗粒的加入与晶须一起产生明显的迭加增韧效果 ,而且对SiCW 的各种增韧机制起到了促进作用。

Si-B(Al)-C-N系非晶和纳米陶瓷材料研究进展

Si-B(Al)-C-N系非晶和纳米陶瓷材料微观结构独特,高温性能优良,在高温结构材料与航天防热领域表现出诱人的应用前景。从Si-B(Al)-C-N系陶瓷的主要制备方法与工艺特点,典型的组织特征和高温性能,以及Si-B(Al)-C-N基复合材料的性能特点等几方面,综述了该系陶瓷材料的研究现状,展望了其发展趋势。

高Si压铸Al合金ADC12的微弧氧化表面改性

利用恒流微弧氧化技术,在以Na2SiO3和Na3PO4为主盐的电解液中,在高硅压铸Al合金ADC12表面制备了 陶瓷膜．显微硬度及耐蚀性能测试表明,陶瓷膜显微硬度(HV)高达1430,能对基体金属提供有效的防护．涡流测厚及SEM研 究显示,该陶瓷膜厚度分布比较均匀,具有双层结构． EDX和XRD分析表明,该微弧氧化陶瓷膜的主要元素组成为O,Al, Si和P;主要相组成为γ-Al2O3和α-Al2O3,同时含有少量χ-AlO23,θ-A1203和Al2SiO5晶体．

工艺因素对B_4C-AlB_(12)-Al复合材料力学性能的影响

采用粉末冶金法,以B粉、Al粉、B4C粉为原料,在高纯氩气保护条件下,烧结制备了B4C-AlB12-Al复合材料。利用XRD和SEM对其物相组成和显微结构进行表征,研究了初始原料中Al加入量、烧结时间、烧结温度对材料力学性能的影响.结果表明:烧结试样中除含有B4C,AlB12,Al外,还含有Al3BC和少量Al2O3相;升高温度和延长烧结时间均不利于提高材料的抗弯强度;随原料中Al加入量的增加,材料的力学性能先增加后降低,原料中Al加入量(质量分数)为39.71%时试样的硬度最高为661.43 MPa,Al加入量为45.85%时抗弯强度最高达64.15 MPa.

自反应电弧喷涂原位合成Ti(C,N)TiB_2Al_2O_3复相陶瓷涂层

以Ti+B4C为反应药芯、Al为外皮材料制备反应型喷涂丝材,探讨利用自反应电弧喷涂技术在45钢基体表面制备复相陶瓷涂层的可行性。以X射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)等方法分析、观察了涂层的组织与结构,测试了涂层的主要力学性能。结果表明:利用制备的药芯丝材进行喷涂试验,可获得由TiB2、TiB、TiC0.3N0.7、TiN、Al2O3、AlN等多相组成的复相陶瓷涂层。涂层呈典型的层状结构,其连续的基体相内弥散分布着离散的第二、第三相。涂层与基体间的结合强度为18.9MPa,涂层的平均显微硬度与弹性模量分别为735.4HV0.2和461.4GPa,摩擦因数在0.45～0.50之间,耐磨性能较基体材料提高3倍以上。

碳/碳复合材料SiC/W-Al-Si涂层微观结构及抗氧化性能

分别采用包埋法、料浆法在碳/碳(C/C)复合材料表面制备了碳化硅(SiC)内涂层、W-Al-Si合金外涂层,借助XRD和SEM分析了所得涂层的物相组成和微观结构,并测试了带有单一SiC涂层、SiC/W-Al-Si双涂层碳/碳复合材料试样在1500℃静态空气中的抗氧化性能。结果表明:富Si的SiC内涂层结构疏松,仅能为碳/碳基体提供数小时的防氧化保护;W-Al-Si合金外涂层主要由WSi2和W(Si,Al)2两相组成;SiC/W-Al-Si双涂层厚度约为100μm,其抗氧化性能明显优于单一SiC涂层,氧化19 h后涂层试样的质量损失未超过5%;有望进一步通过优化W-Al-Si外涂层料浆比例,避免因为与SiC内涂层热膨胀不匹配而产生透性裂纹,从而发挥出超过19 h后SiC/W-Al-Si双涂层的氧化防护潜力。

激光熔覆TiC/Ni-Al基复合涂层的高温稳定性研究

在不锈钢基材上通过激光合成Ni-Cr-Al-Co-X(X=Mo、W、Nb、Ti、C、B)+TiC粉末制备出TiC陶瓷颗粒增强Ni-Al基高温耐磨复合材料涂层,并将试样在1 000℃高温保温50 h。利用光学显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS)显微硬度计对涂层高温时效前后的组织、相成分、硬度进行了对比分析和测试。结果显示:实验条件下,激光熔覆涂层与基材之间没有出现裂纹、孔洞等缺陷,涂层与基材之间仍保持着良好的冶金结合。激光熔覆TiC陶瓷颗粒增强Ni-Al基高温耐磨复合材料涂层具有良好的高温稳定性。

APS制备SiC/Al_2O_3复合陶瓷涂层组织结构及抗烧蚀性能的研究

针对APS制备SiC涂层沉积率低、孔隙率高、在烧蚀考核的过程中出现基体C/C材料被氧化烧蚀的问题,本文设计制备了SiC/Al_2O_3复合陶瓷团聚粉末,采用APS在C/C表面制备了相应的SiC/Al_2O_3复合陶瓷涂层,并选用氧乙炔在1500℃对涂层进行了抗氧化烧蚀性能考核。利用XRD、SEM等检测分析手段对团聚粉末以及涂层的成分及组织进行检测。结果表明,通过在SiC粉末中添加Al_2O_3粉末(SiC:Al_2O_3为3:2),提高了团聚粉末的沉积率以及涂层的致密度,其原因是等离子喷涂过程中Al_2O_3液相对SiC具有良好的包袱保护效果,避免了SiC的分解问题。烧蚀实验表明涂层可以在1500℃烧蚀5 min后,涂层完整,证明氧化物的添加可以封堵孔洞并且抑制氧气的扩散,从而提高涂层抗烧蚀性能。

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^-6mm^3/(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。

Ti-C-Al复合涂层与镁合金基体连接界面微观结构研究

通过LWY400P激光器,用激光熔覆的方法在镁合金表面熔覆一层Ti-C-Al复合陶瓷涂层。原料中钛碳原子比为1∶1,铝含量10%~40%（质量分数）。分别用扫描电镜和能谱分析仪对熔覆层的微观组织、显微形貌和成分分布进行了测定和分析。结果表明,激光熔覆Ti-C-Al复合涂层是典型的快速凝固组织,涂层组织致密,晶粒细小。原料中Al含量对熔覆效果影响很大,Al含量越高,试样致密度越好,通过试验确定了原料中Al的最佳用量。融合区域各元素相互扩散,涂层与基体发生互熔,形成冶金结合,达到强化目的。