TiB2涂层熔盐电沉积制备与表征

炭阴极在铝电解槽中受熔盐和铝液腐蚀而影响寿命,而TiB₂涂层是铝电解槽理想的阴极材料。本文以石墨为基体,在KF-KCl-K₂TiF₆-KBF₄熔盐中以0.4-0.7A.cm_-2^{电流密度、}700-800℃温度电沉积TiB₂涂层,通过XRD衍射仪、SEM-EDS、表面粗糙度测量仪及附着力测试仪对不同电流密度和温度下制备的涂层进行表征。结果表明：在石墨基体上可以得到均匀连贯的TiB₂涂层;增大电流密度、降低电解温度可以细化涂层晶粒,提高涂层致密性;在0.6 A.cm_-²、750℃最优电沉积条件下制得的TiB₂涂层的厚度为229 μm,择优取向为<110>,表面粗糙度为14.85 μm,涂层与石墨基体的结合力为6.39 MPa。     

超音速大气等离子喷涂TiB2-SiC涂层的抗氧化性及耐熔盐腐蚀性能

采用超音速大气等离子喷涂制备全包覆TiB₂-SiC涂层,研究了TiB₂-SiC涂层在400和800 ℃的氧化性能,并探究其氧化机理。对TiB₂-SiC涂层在900 ℃下的抗铝熔盐腐蚀性能进行研究,并探讨其耐熔盐腐蚀机理。结果表明,超音速大气等离子喷涂制备的TiB₂-SiC涂层具有良好的抗氧化性,在400 ℃的氧化速率常数为1.92×10^-5 mg²·cm^-4·s^-1,在800 ℃的氧化速率常数为1.82×10^-4 mg²·cm^-4·s^-1。超音速大气等离子喷涂制备的TiB₂-SiC涂层在900 ℃下具有良好的抗熔盐腐蚀性能,熔盐腐蚀后TiB₂-SiC涂层都保持致密结构,未发生涂层的开裂及剥落。     

氩弧熔敷原位合成TiC-TiB2/Ti基复合涂层组织及性能分析

利用氩弧熔敷技术,在TC4合金表面原位合成了TiC-TiB₂增强镍基复合材料涂层,利用SEM和XRD等方法分析了涂层的显微组织并测试了涂层的显微硬度.结果表明,熔敷组织主要由TiC,TiB₂和Ti(Ni,Cr)组成,TiB₂主要以棒状形式存在;在所形成的TiC-TiB₂/Ti复合材料层中,TiC和TiB₂颗粒分布均匀且尺寸细小;熔敷涂层由表及里组织不同;熔敷层与基体呈冶金结合,无气孔、裂纹等缺陷;涂层的显微硬度达到13.8 GPa,较基体提高了4.5倍.     

TiB2陶瓷粉末纳米化改性及其增强环氧复合涂层的制备与表征

低温条件下,以钛酸丁酯为原料,采用胶溶-回流方法在TiB₂粉体表面包覆纳米TiO₂颗粒。通过SEM、XRD、BET等分析检测方法对复合颗粒的表观形貌、包覆层相成分、比表面积等进行表征。结果显示,纳米TiO₂颗粒均匀离散地包覆在TiB₂粉体表面,包覆层主要为锐钛矿型相,TiB₂粉体纳米化改性后复合颗粒的表面粗糙度显著增加,比表面积较包覆前提高35倍以上。将包覆后的TiB₂粉体引入环氧树脂制备耐磨复合涂层,测得其磨损失重仅为包覆前复合耐磨涂层的50%,其耐磨性显著提高,并初步分析了复合耐磨涂层的摩擦磨损性能、磨损形貌及耐磨机理。     

W含量对自蔓延离心熔铸TiB2-TiC-(Ti,W)C陶瓷组织性能的影响

通过在(Ti+B₄C)体系中引入(WO₃+Al)燃烧体系,进而调整两体系的比例,采用自蔓延离心熔铸工艺成功制备出W系列含量的TiB₂-TiC-(Ti, W)C复合陶瓷。XRD、FESEM和XRD结果显示：陶瓷基体主要由TiB₂、TiC和(Ti, W)C固溶体组成,且随着W含量的增加,(Ti, W)C固溶体体积分数增加,而TiB₂和TiC体积分数减少且晶粒逐渐细化,同时,组织分布趋于均匀。力学性能测试表明,随着W含量的增加,TiB₂-TiC-(Ti, W)C复合陶瓷的相对密度和维氏硬度呈上升趋势,而陶瓷的弯曲强度和断裂韧性先增大后减小,在W含量65%时达到最大值,这是TiB₂作为唯一的增强相体积分数逐渐减少的结果。     

黏结相对YSZ基高温封严涂层沉积效率和热循环性能的影响∗

为解决 YSZ(Y₂O₃ 部分稳定的 ZrO₂ ) 陶瓷基高温封严涂层沉积效率较低和易于过早剥落失效的问题,选择氧化铝 (Al ₂O₃ )、钇铝石榴石(Y₃Al ₅O₁₂ ,YAG)及镁铝尖晶石(MgAl ₂O₄ )为三种高温黏结相,通过喷雾造粒的方法分别制备出 B0(无黏结相)、B1(含 Al ₂O₃ )、B2(含 YAG)和 B3(含 MgAl ₂O₄ )等四种 YSZ 基团聚颗粒,研究黏结相对涂层沉积效率和热循环性能的影响。 结果表明,YAG 的黏附和包裹作用最强,与 B0 型粉末相比,B2 型粉末的沉积效率提高了 181. 49%;热循环过程中不断增长的裂纹扩展驱动力和陶瓷材料的脆性属性是导致陶瓷涂层剥落失效的主要原因,由于 YAG 相的弥散增韧作用,B2 型涂层的断口呈现出类韧窝形貌,与 B0 型涂层相比,B2 型涂层的断裂韧性提高了 39. 76%,热循环寿命提高了 43. 68%。 YAG 黏结相的添加显著地提高了 YSZ 陶瓷基高温封严涂层的沉积效率,同时较好地提高了涂层的热循环寿命。     

不同粒度银粉的Ag-TiB2 触头材料电弧侵蚀行为

采用不同粒度的银粉和放电等离子烧结工艺制备了Ag-4% TiB₂（质量分数,下同）触头材料,测量了Ag-4% TiB₂触头材料的致密度、导电率和硬度,并在真空下对Ag-4% TiB₂触头材料进行了电弧侵蚀实验。采用扫描电子显微镜对Ag-4% TiB₂触头材料电弧侵蚀后的表面形貌进行了表征,采用TDS-2014双通道数字存储示波器记录了燃弧波形,并计算了燃弧时间,对电弧侵蚀机理进行了探讨。结果表明,Ag-4% TiB₂触头材料的致密度、导电率和硬度均随着Ag粒度的降低而增加。另外,采用细银粉制备的Ag-4% TiB₂触头材料具有较长的燃弧时间、较大的侵蚀面积和较浅的蚀坑,表明细小的Ag颗粒有助于电弧分散,能够提高材料的耐电弧侵蚀性能。     

中间钛片对TiB2基陶瓷/钛合金梯度复合材料组织性能的影响

在钛合金与陶瓷粉末之间引入厚度从0.5mm到1.5mm的中间钛片,采用自蔓延离心熔铸工艺快速制备出了TiB₂基陶瓷/钛合金梯度复合材料,经过XRD, FESEM 和 EDS分析表明,添加钛片对陶瓷相没有明显的影响,但随着中间钛片厚度的增加,不仅细化陶瓷基体并改善其组织均匀性,而且增加了梯度界面厚度,减小甚至消除了钛合金基底热影响区。同时,热真空条件下液态陶瓷与钛合金之间发生熔化连接和原子互扩散,进而在凝固后期诱发TiB₂与Ti液的包晶反应 ,TiB自Ti液中的析晶反应和TiB与Ti液的共晶反应,实现了TiB₂的消减及TiB的生长,不仅改善了界面的残余应力,而且获得了陶瓷/钛合金多尺度多层次复合。界面组织结构的梯度演化与陶瓷/钛合金的热匹配不仅使梯度材料的硬度呈连续变化,而且使界面剪切强度达到了316±25 MPa。     

原位合成高含量TiB2/SiC复合材料的显微组织与性能

以SiC、TiO₂和B₄C为主要原料,采用原位合成法一步烧结制备高含量TiB₂/SiC复合材料,利用维氏硬度计、电子万能试验机、伏安电阻计、金相显微镜和电子扫描电镜,研究TiB₂含量对TiB₂/SiC复合材料力学性能、体积电阻率与显微组织的影响。结果表明：随着TiB₂含量的增加,复合材料的开口气孔率先降低后增加、抗折强度和断裂韧性均先增大后减小、维氏硬度逐渐增加、电阻率先快速下降后趋于稳定、TiB₂颗粒的平均粒径逐渐增大。1950 ℃烧结后,TiB₂含量为40 wt% 的复合材料性能最佳,其开口气孔率、抗折强度、断裂韧性和体积电阻率分别为0.56％、412 MPa、5.77 MPa?m_1/2和2.6×10_-1(Ω?cm)。     

不同方法制备的AgSnO2TiB2 电接触材料的微观结构和电弧侵蚀行为

分别采用球磨法、可溶性淀粉模板法和滤纸模板法制备了AgSnO₂TiB₂复合粉末,并利用火花等离子体烧结技术（SPS）制备了块体材料。对Ag4%SnO₂4%TiB₂（质量分数）电接触材料的物理性能和电弧侵蚀特性进行了研究。结果表明,模板的空间限域效应有效地改善了增强相在基体中的均匀分散,提高了Ag4%SnO₂4%TiB₂接触材料的导电率和硬度。与球磨法相比,滤纸模板法和淀粉模板法制备的Ag4%SnO₂4%TiB₂复合材料的电导率分别增加了12.18倍和9.60倍, 显微硬度分别增加了17.10%和33.94%。滤纸模板更有利于SnO₂和TiB₂的均匀分散,减少集中电弧侵蚀和飞溅损失,因此具有更好的抗弧蚀性。     

Effects of TiB2+TiC content on microstructure and wear resistance of Ni55-based composite coatings produced by plasma cladding

TiB₂-TiC reinforced Ni55 matrix composite coatings were in-situ fabricated via plasma cladding on steels using Ti, B₄C, and Ni55 as precursor materials at different proportions. Effects of TiB₂+TiC content of ceramics phase on the microstructure and wear resistance were studied. The results showed that ceramic phases TiB₂ and TiC were in-situ synthesized by plasma cladding, and the ceramic phase content significantly affected tribological performance and the wear mechanism of coatings under different loads. The composite ceramics protected coatings from further delamination wear by crack-resistance under a load of 30 N. Severe abrasive wear and adhesive wear were prevented when the load increased to 60 N because of the high hardness and strength of ceramic phases. Moreover, a compacted layer appeared on the wear surface of coatings with high content of ceramic phases, which effectively decreased the friction coefficient and wear rate. The TiB₂-TiC composite ceramics significantly improved the wear performance of metal matrix composite coatings by different mechanisms under loads of 30 and 60 N.     

Tribological Properties of HVOF-Sprayed TiB<Subscript>2</Subscript>-NiCr Coatings with Agglomerated Feedstocks

Boride materials have drawn great attention in surface engineering field, owing to their high hardness and good wear resistance. In our previous work, a plasma-sprayed TiB₂-based cermet coating was deposited, but the coating toughness was significantly influenced by the formation of a brittle ternary phase (Ni₂₀Ti₃B₆) derived from the reaction between TiB₂ and metal binder. In order to suppress such a reaction occurred in the high-temperature spraying process, the high-velocity oxygen-fuel spraying technique was applied to prepare the TiB₂-NiCr coating. Emphasis was paid on the microstructure, the mechanical properties, and the sliding wearing performance of the coating. The result showed that the HVOF-sprayed coating mainly consisted of hard ceramic particles including TiB₂, CrB, and the binder phase. No evidence of Ni₂₀Ti₃B₆ phase was found in the coating. The mechanical properties of HVOF-sprayed TiB₂-NiCr coating were comparable to the conventional Cr₃C₂-NiCr coating. The frictional coefficient of the TiB₂-NiCr coating was lower than the Cr₃C₂-NiCr coating when sliding against a bearing steel ball.     

热喷涂TiB2-Ni复合涂层组织结构和力学性能

采用团聚烧结方法制备TiB₂-Ni复合粉末喂料,并采用大气等离子喷涂和高速火焰喷涂两种喷涂方法制备了TiB₂-Ni涂层,比较分析了两种涂层的显微组织、物相组成、孔隙率、硬度和断裂韧性.结果表明,与等离子喷涂相比,高速火焰喷涂制备的TiB₂-Ni涂层具有更高的致密度,TiB₂含量,硬度和断裂韧性.两种涂层中TiB₂都没有发生明显的脱硼,氧化,但等离子喷涂过程中TiB₂向金属相中发生了溶解生成了大量脆性Ni₂₀Ti₃B₆相,并降低了涂层中TiB₂的含量,这是涂层硬度和断裂韧性相对较低的主要原因.     

HiPIMS复合热处理制备高纯Ti2AlC MAX相涂层

Ti₂AlC MAX相涂层是一类兼具金属和陶瓷特性的具有密排六方结构的高性能陶瓷涂层,在电接触、高温防护、宽温域摩擦等领域具有广阔的应用前景。然而MAX相涂层的成相成分窗口窄,性能受杂质相影响大,实现高纯、致密Ti₂AlC MAX相涂层的制备目前仍存在挑战。考虑沉积气压与溅射等离子体能量密切相关,采用高功率脉冲复合直流磁控溅射技术在钛合金基体上制备了TiAl/Ti-Al-C涂层,经后续热处理退火得到高纯Ti₂AlC MAX相涂层,重点研究不同沉积气压对涂层退火前后的成分、微观结构以及力学性能的影响和作用机制。结果表明,随着气压不断增大,沉积态涂层厚度先增加后减少。其中低沉积气压下沉积态涂层退火后,结构中除了Ti₂AlC MAX相外,还含有一定量杂质相;而在高气压下沉积态涂层退火后几乎全部转变为Ti₂AlC MAX相,呈现高纯、表面光滑致密的MAX相涂层特征。相较于沉积态涂层,退火后的涂层硬度变化不大,但由于生成了Ti₂AlC MAX相,涂层弹性模量有所提高...     

Low temperature deposition of tribological coatings

The results of microstructural and tribological studies performed on sputter-deposited coatings of ZrO₂·2OY₂O₃, TiB₂ and B-18wt.%Si are reported. In each case, deposition parameters were identified that offered good tribological properties while maintaining low deposition temperatures (below 400 °C) to avoid distortion and softening of previously heat-treated substrates. Zirconia deposits were prepared with a pronounced columnar microstructure that provided excellent thermal fatigue and wear resistance, making them candidates for heat engine applications. The TiB₂ coatings were the hardest coatings prepared. These provided good wear resistance on steel substrates. The B-Si coating displayed excellent wear resistance and good adherence to copper and aluminum alloys.     

Thermal spraying of reactive materials to form wear-resistant composite coatings

The dispersion of more than 20 vol.% submicrometer ceramic particles within a metallic matrix and the deposition of such a cermet to form a thick and tough coating presents problems. Most of the coating techniques have failed in attempting to homogeneously disperse very fine and hard particles in large amounts while avoiding their decomposition or reaction with the metal matrix during the deposition process. A simple and efficient method has been developed for producing ceramic-containing composite coatings. It consists in synthesizing cermet-based materials and in depositing them by a rapid solidification process such as thermal spraying. Boride- and carbide-based materials have been successfully obtained by plasma spraying reactive powders comprising the basic reagents. These materials, with a microstructure of submicrometer ceramic particles dispersed in a metallic matrix, exhibit good wear-resistant properties (abrasion and sliding wear). Finally, reactive core wire arc spraying is suggested as a flexible way to produce coatings containing up to 25 vol.% TiB₂.     

Research progress in TiB<Subscript>2</Subscript> wettable cathode for aluminum reduction

Titanium diboride wettable cathodes are regarded as ideal for aluminum reduction because of their excellent wettability with molten aluminum. The TiB₂ inert wettable cathode materials for aluminum reduction may be divided into three groups: pure TiB₂ ceramic cathode, TiB₂ composite cathode, and TiB₂ coating. This paper briefly describes international research progress on TiB₂ inert wettable cathodes as well as problems faced, and concentrates on the activities of Central South University, Changsha, China, in researching the ambient-temperature solidified TiB₂ cathode coating. At the same time, the results of the coating applied in many aluminum smelters in China are presented, and the pattern of cathode surface of 160 kA cells coated with the ambient-temperature-solidified TiB₂ cathode coating after one year operation is discussed in comparison with the normal cells.     

Comparison of vacuum and pressure-assisted sintering of TiB2-Ni

A relatively new generation of cermet materials, based on TiB₂-Ni, has been investigated. These borides currently are being examined for industrial applications with the aim of exploiting their excellent wear resistance. Optimization of the liquid-phase sintering process for a TilB₂-Ni composition was studied. The mechanical properties of cermet materials prepared using vacuum and pressure sintering techniques were determined. Criteria for optimal sintering conditions were established according to hardness, strength, and fracture toughness properties.     

Titanium diboride composite with improved sintering characteristics

Titanium diboride (TiB₂) and its ceramic composites were prepared by hot pressing process. The sintering process, phase evolution, microstructure and mechanical properties of TiB₂ ceramics prepared by using different milling media materials: tungsten carbide (WC/Co) or SiAlON was studied. It was found that the inclusion of WC/Co significantly improved the sinterability of the TiB₂ ceramics. A core/rim structure with pure TiB₂ as the core and W-rich TiB₂, i.e. (Ti,W)B₂ as the rim was identified. Microstructure analysis revealed that this core/rim structure was formed through a dissolution and re-precipitation process. In addition, silicon carbide (SiC) was also introduced to form TiB₂–SiC composites. The addition of SiC as the secondary phase not only improved the sinterability but also led to greatly enhanced fracture toughness. The optimum mechanical properties with Vickers hardness ~ 22 GPa, and fracture toughness ~ 6 MPa m^1/2 were obtained on TiB₂–SiC composites milled with WC/Co.