等离子喷涂ZrO2热障涂层的抗热震性能

为了进一步了解等离子喷涂ZrO2涂层的制备及失效控制措施,提高涂层的使用寿命,研究了涂层在水淬和火焰喷烧两种条件下的抗热震性能.结果表明:水淬条件下垂直裂纹主要分布在距涂层中心12mm范围内,随热震次数的增加,垂直裂纹最终进入次表层,靠近中心处裂纹扩展较快;火焰喷烧条件下垂直裂纹分布在距涂层中心10 mm范围内,随热震次数的增加,裂纹在表面层和次表层界面处发生偏转,中心处裂纹扩展较快;火焰喷烧条件下涂层的抗热震性能优于水淬下,涂层中孔隙的存在加速了两种条件下裂纹的扩展.     

等离子弧喷涂Al2O3陶瓷涂层低温抗热震性能的研究

为研究等离子弧喷涂Al2O3陶瓷涂层的低温抗热震性能,对不同结构的涂层进行了600 ℃低温热震试验,并分析、探讨了涂层的热震失效机制.结果表明,Al2O3陶瓷涂层低温下热震失效是由层间裂纹或层内裂纹引起的.对于单一Al2O3涂层,涂层与基体的界面是最薄弱处,层间裂纹的萌生及扩展导致涂层自界面处脱落;对于有FeCrAl金属过渡层的涂层,层内粒子间的结合是最薄弱处,层内片层间裂纹的萌生、扩展导致涂层局部脱落.在陶瓷工作层与基体间增加金属过渡层可有效地缓和涂层界面处的热应力,阻碍裂纹的形成及扩展,从而提高涂层的抗热震性能.     

大气等离子喷涂工艺参数对Al2O3涂层性能的影响

为了提高燃烧器工艺烧嘴的使用寿命,在UMCo-50基材表面大气等离子喷涂Al2O3层。采用正交试验法对喷涂工艺参数进行了优化,运用微观形貌分析、X射线衍射分析并结合强度及显微硬度等测试方法,系统研究了喷涂主气流量、功率和送粉量对AI2O3涂层综合性能的影响规律。结果表明:喷涂主气流量、功率和送粉量对Al2O3涂层性能具有交互性影响,在40L/min Ar,48 kW和30g/min条件下可以获得性能较好的Al2O3涂层,极大地提高了UMCo-50基材的抗高温氧化和耐磨性能,使之具有广阔的应用前景。     

Al2O3对高速火焰喷涂镍基涂层抗热疲劳性能的影响

为了提高连铸结晶器的使用寿命和生产效率,利用高速火焰喷涂(HVAF)技术在铜基体上制备了镍基涂层,探讨了喷涂粉末中不同比例的Al2O3对镍基涂层抗热疲劳性能的影响及其机理.结果表明:添加50%Al2O3的镍基涂层,抗热疲劳性能得到了明显的提高;Al2O3颗粒的添加,有效地增加了涂层的压应力,提高了涂层与铜基体之间的结合强度,从而显著地提高了涂层的抗热疲劳性能.     

等离子喷涂纳米Al2O3/TiO2复合陶瓷涂层的显微组织与性能

采用液相喷雾造粒方法将纳米级Al2O3/TiO2团聚成微米级颗粒,制备了适用于等离子喷涂的陶瓷复合粉体,并利用等离子喷涂技术成功的制备出了含有纳米结构的陶瓷涂层.利用X射线衍射、扫描电镜、透射电镜和显微硬度计等设备对涂层的微观结构和性能做了初步的检测.结果表明,涂层中含有适当比例的未熔或半熔的纳米颗粒,涂层的硬度、韧性和耐磨性等性能与普通涂层相比都有了较大提高.     

纳米Al2O3封孔对电弧喷涂3Cr13涂层耐腐蚀性能的影响

采用电弧喷涂技术在Q235钢基体上制备了约150μm厚的3Crl3涂层,并采用3种添加不同含量的纳米AlO3异丙醇溶液的有机硅树脂对其进行封孔处理,利用光学显微镜（OM）、扫描电镜（SEM）和X射线衍射仪（XRD）对涂层的微观组织和物相组成进行分析,采用全浸泡腐蚀、乙酸盐雾腐蚀以及电化学腐蚀试验研究了未封孔及封孔涂层的耐腐蚀性能。结果表明：3Crl3涂层的物相组成主要为α—Fe（Cr）和Cr2O3涂层为典型的层状堆积结构,孔隙率约为11％;涂层封孔后的耐腐蚀性能明显优于未封孔涂层的,而且添加质量分数为6％的纳米AIz03异丙醇溶液的有机硅封孔剂对3Crl3涂层耐腐蚀性能的提高最为显著。     

等离子喷涂Fe/Al2O3涂层的微观结构及介电性能

以往将等离子喷涂层用于介电性能的研究较少。采用大气等离子喷涂在石墨表面制备了一系列Fe/Al2O3陶瓷涂层。采用表面分析技术研究了不同Fe/Al2O3含量涂层的微观结构和在8.2～12.4GHz频率范围的介电性能,探讨了Fe含量对涂层相组成和微观结构以及介电性能的影响。结果表明:Fe/Al2O3陶瓷涂层中Fe粉和气孔分布均匀;随着Fe粉量的增加,颗粒热导率变大,涂层中未熔融颗粒减少,γ-Al2O3随之增加,气孔率逐渐下降;涂层的复介电常数随着Fe粉含量的增加而增大。     

纳米掺杂Al2O3/ZrO2等离子喷涂涂层组织结构研究

利用大气等离子喷涂技术,在N80钢基体上制备纳米掺杂Al2O3/ZrO2热障涂层。利用XRD、SEM等观察分析了纳米掺杂Al2O3/ZrO2粉末及等离子喷涂涂层组织形貌及结构,结果表明,Al2O3/ZrO2等离子喷涂粉末是由纳米包覆微米级粒子及少量的纳米团聚体球团粒子构成。纳米掺杂等离子喷涂Al2O3/ZrO2涂层的微观组织形貌复杂,存在着纳米柱状晶薄壳内包裹着微米级柱状晶、未熔化的ZrO2陶瓷粒子嵌镶在晶体内部的独特晶内结构。涂层主要由α-Al2O3及亚稳四方相t,-ZrO2相构成。     

稀土氧化物添加剂对Al2O3等离子喷涂层的影响

在Al2O3陶瓷材料中添加不同含量的稀土氧化物添加剂，探讨了稀土氧化物对等离子喷涂Al2O3涂层组织、结合强度和抗热冲击性的影响。研究结果表明，加入适量稀土氧化物添加剂后可降低涂层中的孔隙率和气孔尺寸，减少涂层内应力在气孔边缘的应力集中，提高了Al2O3涂层的结合强度和抗热冲击性能。     

Sliding Wear Behavior of Plasma Sprayed Alumina-Based Composite Coatings against Al2O3 Ball

The sliding wear behaviors of a single layer AI2O3-30 wt pct ZrO2, a double layer AI2O3-30 wt pct ZrO2/Ni-Cr and a single layer AI2O3-13 wt pct TiO2 coating deposited on low carbon steel by plasma spraying were investigated under lubricated conditions with various normal loads. The plastic deformation, detachment and pull out of splats were involved in the wear process of the studied coatings under test conditions. Crack propagation was found in AI2O3-13 wt pct TiO2 under loads of 70 and 100 N and in AI2O3-30 wt pct ZrO2/Ni-Cr under a load of 130 N. While increasing the normal load, the wear rates of AI2O3-30 wt pct ZrO2 and AI2O3-30 wt pct ZrO2/Ni-Cr slightly increased, the wear rate of AI2O3-13 wt pct TiO2 increased rapidly. The results showed that the Ni-Cr bonding layer improved the wear resistance of the coating system even it is relatively thin compared with the outer coating layer. The influence of this bonding layer on wear behavior of the coating increased as increasing the normal load.     

等离子喷涂CNTs/Al2O3复合涂层力学性能研究

通过等离子喷涂工艺制备了不同碳纳米管含量的CNTs/Al2O3复合涂层,系统研究了碳纳米管含量对涂层孔隙率、洛氏硬度和断裂韧性的影响规律。实验结果表明:采用喷雾干燥工艺制备的CNTs/Al2O3颗粒为球形,CNTs均匀分布在团聚颗粒的表面;部分CNTs经等离子喷涂后保留在沉积涂层内部并且与Al2O3基体形成冶金结合,起到一定桥接作用。涂层孔隙率和洛氏硬度值均随CNTs含量的增加呈现降低的趋势。随CNTs含量从6%(质量分数)增加到12%(质量分数),CNTs增韧效果的增强和涂层孔隙率的降低导致涂层断裂韧性值从48MPa增加到90MPa。     

等离子喷涂纳米Al2O3-TiO2复合陶瓷涂层的研究现状

等离子喷涂纳米Al2O3-TiO2复合陶瓷涂层具有耐磨、耐腐蚀、抗热氧化等优良性能,因而成为目前纳米涂层领域的研究热点之一。归纳了纳米结构Al2O3-TiO2喂料的制备方法,介绍了纳米结构涂层的显微结构和力学性能(断裂韧性、显微硬度、结合强度等),分析了纳米结构涂层的抗热氧化性和摩擦学性能,综述了等离子喷涂纳米Al2O3-TiO2复合陶瓷涂层的研究现状,讨论并展望了其未来的发展方向和应用前景。     

火焰喷涂Al2O3/TiO2-NiCrBSi阶梯热障涂层的热冲击失效分析

研究了氧乙炔火焰喷涂制备的Ａl2O3/TiO2-NiCrBSi阶梯热障涂层在水淬热冲击条件下的失效行为,结果表明,涂层的抗热层冲击能力随梯度成分间隔的减小而增强,其失效是由于涂层层间裂纹和层内裂纹和层内裂纹共同作用的结果,对于成分梯度化较好的涂层,层内裂纹扩展导致网状裂纹是失效的主要原因,层间成分间隔大,失效则是以层间裂 的快速扩展而导致涂层整体剥落的主要原因,当成分间隔介于以下二者时,层内裂纹和层间裂纹共同作用,导致涂层以局部脱或剥形式失效。     

Sintering process of Y2O3 and Al2O3-doped Si3N4

The sintering process of Y₂O₃- and Al₂O₃-doped Si₃N₄ has been investigated by dilatometry and microstructural observations. The densification progressed through three processes. The bulk density increased to 85% theoretical without the formation of -Si₃N₄ in the initial process. The densification once terminated after the second process. The / transformation of Si₃N₄ and the related formation of prismatic grains reduced the densification rate in the second process, although the grain size and the aspect ratio were very small. The final process was the densification of -Si₃N₄, where the fibrous grains grew remarkably. The kinetic order for the densification of -Si₃N₄ indicated a diffusion-rate controlling mechanism with the activation energy of 244 kJ mol^–1 (<1450 ° C) and 193 kJ mol^–1 (>1450 ° C). The influence of heating rate on the grain growth was characterized by a parameter derived from kinetic parameters. The relationships between grain growth and densification behaviour have also been discussed.     

Pressureless sintering of Si3N4 with Y2O2 and Al2O3

Pressureless sintering of Si₃N₄ with Y₂O₃ and Al₂O₃ as additives was carried out at 1750°C in N₂ atmosphere. Si₃N₄ materials which had more than 92% relative density were obtained with 20wt% addition of additives. The flexural strength of as-sintered materials containing 5 to 8.6wt% Al₂O₃ and 15 to 11.4wt% Y₂O₃ was in the range of 480 to 560 MPa at room temperature. The glassy grain-boundary phase of as-sintered materials crystallized to 3Y₂O₃ · 5Al₂O₃ (YAG), Y₂O₃ · SiO₂ (YS), Y₂O₃ · 2SiO₂ (Y2S) and 10Y₂O₃ · 9SiO₂ sd Si₃N₄ (NA) by heat-treatment at 1250° C for 3 days. A specimen containing 15wt% Y₂O₃ and 5wt% Al₂O₃ sintered at 1750° C for 4 h was heat-treated at 1250° C for 3 days to precipitate YAG and YS. The nitrogen concentration of the grain-boundary glassy phase of the specimen was found to be very high, and therefore the flexural strength of the crystallized specimen scarcely decreased at elevated temperatures (the flexural strength of this specimen is 390 MPa at room temperature and 360 MPa at 1300° C). Resistance to oxidation at 1200° C of the specimen was good as well as the flexural strength, compared with that of as-sintered materials.