等离子喷涂ZrO2热障涂层的抗热震性能研究

采用等离子喷涂方法在304不锈钢表面喷涂NiCoCrAIY2O3+(ZrO2+7%Y2O3)陶瓷热障涂层,模拟航空发动机涡轮叶片工作环境,研究涂层在加热和空气冷却条件下的抗热震性能.结果表明:喷涂后的涂层内部产生大量微观裂纹,随着热震次数的增加,陶瓷层内部的纵向微观裂纹通过大孔隙的连通方式逐渐在涂层内部扩展.ZrO2陶瓷喷涂后涂层主要以四方相和部分立方相组成,当涂层在热震40次时,陶瓷中的部分四方相向单斜相转变,并伴随着体积的变化,易在涂层中形成新的裂纹并加快原有裂纹的扩展.     

CeO2添加剂对等离子喷涂ZrO2涂层抗热震性的影响

采用SEM,EPMA和热震方法,研究了CeO2添加剂对等离子喷涂ZrO2i涂层抗热震性能的影响。结果表明：当CeO2由0增加到9.0%（质量分数,下同）时,涂层的抗热震起裂次数和失效次数分别由32次和46次增加到76次和105次;继续增加CeO2,涂层的抗热震性能急剧下降。ZrO2 9.0?O2涂层在热循环中形成的网状微裂纹,不仅可降低涂层中的应力,也可提高涂层开裂的临界温差,从而可改善其抗热震性能。     

激光表面重熔对ZrO_2-8wt%Y_2O_3热障涂层组织与抗热震性能的影响

采用等离子喷涂设备在H13热作模具钢表面制备氧化钇部分稳定的氧化锆(ZrO2-8 wt%Y2O3)热障涂层,并用CO2横流激光器对热障涂层进行表面重熔处理,并采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、热震试验等手段研究激光重熔前后热障涂层的微观结构及其抗热震性能的变化。结果表明,重熔前后涂层均由四方结构钇锆氧化物和立方相的氧化锆组成,重熔后涂层结晶度增加,晶粒有长大现象。激光重熔后涂层产生明显分层,表层组织孔隙和裂纹明显减少,裂纹呈网状且沿晶界分布,重熔涂层内部仍保持等离子喷涂典型结构。激光重熔后涂层孔隙率降低了67%,涂层的抗热震性能也显著提高。     

等离子喷涂CeO2-Y2O3稳定ZrO2陶瓷涂层耐高温铁水热震研究

采用等离子喷涂方法在304不锈钢表面制备NiCoCrAlY2O3/(ZrO2+25 %CeO2+3 %Y2O3)耐高温涂层,模拟铸造模具表面的工作环境,涂层在1350 ℃铁水液中加热热震和在炉中大气环境下加热热震后,对涂层组织结构和物相变化进行了对比研究.结果表明:涂层在铁水中热震后,涂层内部的大量裂纹交联在一起,在陶瓷层与粘结层界面靠近陶瓷层一侧出现尺寸近10 μm宽的裂纹,陶瓷层中的部分四方相向单斜相和立方相转变,铁水中部分元素与陶瓷元素发生了扩散并生产新相.     

高速电弧喷涂FeMnCr/ZrO2复合涂层组织和抗热震性能的研究

为了研究FeMnCr／ZrO2复合涂层的抗热震性能及失效机理,采用高速电弧喷涂技术在20#钢表面制备了FeMnCr／ZrO2复合涂层。利用光学显微镜（OM）、场发射扫描电子显微镜（FE—SEM）、能谱分析（EDS）等方法分析表征了复合涂层的微观组织和抗热震性能。试验结果表明：ZrO2陶瓷相以游离态团状形式存在于涂层中,游离态团状中ZrO2晶粒呈“马赛克”结构均匀分布;FeMnCr／ZrO2复合涂层热震过程中,涂层氧化起源于层间结合处,且沿着金属结晶相以“网状”形式向内扩展。热震破坏形式为涂层从基体上整体脱落,但是涂层表面无裂纹出现。     

等离子喷涂氧化钇涂层的组织结构

利用大气等离子喷涂技术在铝基体上制备了氧化钇涂层,采用扫描电镜、X射线衍射仪和金相显微镜对涂层的组织结构进行分析.结果表明:利用等离子喷涂制备的氧化钇涂层没有裂纹,比较致密,其孔隙率为5.58%;涂层由立方相和单斜相组成,喷涂粉末的相结构影响涂层的物相,粉末中的单斜相促进等离子喷涂过程中立方→单斜相变过程.     

丙烷流量对火焰喷涂TiB_2-50Co涂层抗热震性能的影响

将在不同丙烷流量条件下采用超音速火焰喷涂技术制备的3种TiB2-50Co进行热震试验,研究3种涂层在600℃不同热震循环次数和800℃条件下的抗热震性能,通过扫描电子显微镜和X射线衍射仪对3种涂层在不同条件下热震后的表面和截面形貌及物相结构进行分析,通过水淬法测试涂层的抗热震性能。结果表明,在600℃条件下,随着热震次数的增加,涂层中的表面和截面裂纹扩展随之更长而深,并在热震循环次数为150次时涂层中出现了网状或交叉裂纹;在800℃条件下,涂层热震失效循环次数明显减少,涂层中裂纹扩展更为严重,其中No.3涂层(丙烷流量为36L/min)抗热震性能最差。通过对3种涂层在不同热震条件后的XRD分析可知,涂层的主要物相为TiB2和Co两相,并发现涂层中存在一定的TiO2氧化相。     

SiO2添加剂对等离子喷涂Al2O3涂层抗热震性的影响

通过在Ａｌ２Ｏ３陶瓷粉末中添加不同数量的ＳｉＯ２，探讨其对等离子喷涂涂层抗热震性的影响。结果表明，在等离子喷涂Ａｌ２Ｏ３涂层中添加３％ＳｉＯ２后，热震起裂次数及热震失效次数均得到明显提高。其原因是适量ＳｉＯ２，能明显增加Ａｌ２Ｏ３涂层中的气孔和微裂纹。气孔尺寸均匀，直径在１～２μｍ以内，微裂纹以细网状分布于涂层薄片内。在热震过程中，气孔与微裂纹缓解涂层内应力，延缓了裂纹的扩展，故能显著提高涂层的抗震性能。但添加过量ＳｉＯ２后，由于Ａｌ２Ｏ３与ＳｉＯ２热膨胀系数差异过大，易造成应力集中，产生粗大裂纹，另外，气孔率过大，降低了抗热震性能。     

SiO2添加剂对8%Y2O3稳定的ZrO2涂层热震前后表面形貌的影响

在8％Y2O3稳定的ZrO2陶瓷涂层中添加SiO2，使陶瓷涂层的抗热震性能得到提高，这主要是SiO2的加入使涂层抗热震前后的表面形貌发生了很大的变化。由于ZrO2与SiO2热膨胀系数不同，使涂层利于产生细微的网状裂纹，增加了微裂纹密度和孔隙，从而降低了涂层的弹性模量，释放了涂层中的应力，使涂层的抗热震失效能力得到提高。其中，SiO2加入量为3％(质量分数)效果最佳，过量的加入，会使孔洞加大，促进裂纹的扩展、断裂，不利于提高涂层的抗热震性能。     

丙烷流量对超音速火焰喷涂TiB_2-25Ni涂层抗热震性能的影响

采用超音速火焰喷涂技术(HVOF)在3种丙烷流量(30,36和42 L/min)下将机械球磨后的TiB_2-25Ni颗粒沉积在Q235钢表面上获得不同涂层,将涂层在600℃(50次、100次、150次)和800℃工况下进行热震试验,研究涂层的抗热震性能。采用扫描电镜(SEM)表征热震后涂层的表面和截面形貌以分析热震后的裂纹产生和扩展情况,通过X射线衍射技术(XRD)分析热震后涂层的物相演变规律。研究结果发现,3种涂层在600℃热震条件下随着热震循环次数的增加,涂层中裂纹扩展的愈加严重,且在热震150次后出现了纵向和横向裂纹,并且以丙烷流量为36 L/min时涂层失效最快。通过在800℃涂层热震后发现,涂层失效更快,涂层热震循环次数明显降低,并且在涂层表面出现了明显的网状式裂纹,在涂层截面中裂纹扩展的更为强烈,并延伸至涂层和基体的界面处,从而导致腐蚀介质(水或空气)进入至裂纹中使基体腐蚀,在交界处产生了明显的腐蚀产物。通过对涂层在不同热震条件后的XRD分析发现,3种涂层的主要物相仍然是TiB_2和Ni,热震后涂层表面氧化物增多。     

激光重熔纳米氧化锆热障涂层的抗热冲击性能

采用纳米氧化锆团聚粉末和等离子喷涂技术制备了纳米氧化锆涂层,试验研究了激光重熔工艺参数(激光比能量)对纳米氧化锆涂层抗热冲击性能的影响.结果表明,激光重熔工艺参数对重熔涂层的抗热冲击性能影响显著,采用合适的工艺参数(激光比能量),可以使重熔涂层获得最佳的抗热冲击性能.不同激光重熔工艺参数处理的涂层形成的组织结构不同,使得涂层的抗热冲击性能不同.合适的激光重熔工艺参数下涂层表现出高的抗热冲击性能,主要是因为重熔后的涂层组织结构有利于热应力的释放以及其相结构在高温冲击下具有良好的稳定性.     

纳米氧化锆热障涂层组织结构和抗热冲击性能分析

采用大气等离子喷涂技术制备了纳米氧化锆热障涂层和常规热障涂层.利用FESEM和XRD对纳米氧化锆热障涂层的组织结构和物相组成进行分析.系统研究了两种热障涂层的抗热冲击性能.微观组织分析结果表明,纳米氧化锆热障涂层展现出独特的纳米—微米复合结构,包括柱状晶和未熔融或部分熔融纳米颗粒.非平衡四方相是涂层的主要物相.抗热冲击性能试验结果表明,纳米氧化锆热障涂层拥有更为优越的抗热冲击性能,这主要得益于其相对致密的结构以及微裂纹、纳米晶粒、小孔径孔隙的应力缓释作用.热应力失效是涂层失效的主要原因.     

Thermal Failure of Nanostructured Thermal Barrier Coatings with Cold-Sprayed Nanostructured NiCrAlY Bond Coat

Nanostructured thermal barrier coatings (TBCs) were deposited by plasma spraying using agglomerated nanostructured YSZ powder on Inconel 738 substrate with cold-sprayed nanostructured NiCrAlY powder as bond coat. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured TBCs. For comparison, the TBC consisting of conventional microstructure YSZ and conventional NiCrAlY bond coat was also deposited and subjected to the thermal shock test. The results showed that nanostructured YSZ coating contained two kinds of microstructures; nanosized zirconia particles embedded in the matrix and microcolumnar grain structures of zirconia similar to those of conventional YSZ. Although, after thermal cyclic test, a continuous, uniform thermally grown oxide (TGO) was formed, cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of nanostructured and conventional TBCs mainly occurred through spalling of YSZ. Compared with conventional TBCs, nanostructured TBCs exhibited better thermal shock resistance.     

爆炸压涂制备纳米氧化锆涂层及其组织与性能研究

运用爆炸压涂技术在钢基体上制备了较大面积的纳米氧化锆涂层。利用扫描电镜、X射线衍射等手段研究了纳米氧化锆涂层的微观组织、孔隙率和晶粒度。结果表明,制备的纳米氧化锆涂层结构致密,涂层的孔隙率为5%;与基体结合紧密;爆炸压涂前后氧化锆成分未发生变化;涂层中的氧化锆仍然以稳定的单斜相存在,不存在立方相;涂层中的氧化锆晶粒与粉末晶粒尺寸基本一致。爆炸压涂制备的陶瓷涂层能够保持纳米粉末材料的尺寸和特性。     

Thermal shock behavior of nanostructured and conventional Al2O3/13 wt%TiO2 coatings fabricated by plasma spraying

The thermal shock behavior of three kinds of Al₂O₃/13 wt%TiO₂ coatings fabricated by plasma spraying was studied in this paper. One kind of those coatings was derived from conventional fused and crushed feedstock powder available commercially; the other two kinds of coatings were derived from nanostructured agglomerated feedstock powders. These two nano coatings possess moderate pores and pre-existing microcracks, they were composed of fused structure and three-dimensional net or skeleton-like structure. For conventional coatings, the pores and pre-existing cracks were bigger, sharp-point and mostly distributed between splats. Thermal shock tests for the three coatings were performed by water quenching method. Testing result showed the two kinds of nano coatings had much higher thermal shock resistance than the conventional coatings. The improved thermal shock resistance for nano coatings could attribute to their improved microstructure and crack propagation mode. The damage evolution and failure mechanism of coatings was quite different at thermal shock temperature of 650 °C and 850 °C, which was explained by a simple model. Different crack propagating modes in nanostructured and conventional coatings during thermal shock tests were due to their different microstructures in these two kinds coatings. The stress state of coating surfaces during the thermal cycles was also discussed in this paper.     

Nb-Hf合金表面Si-Ti-Cr硅化物涂层在大气和真空中的高温热震性能

为了提高Nb-Hf合金的高温热震性能,采用浆料烧结和高温渗透法制备了Si-Ti-Cr硅化物涂层,对比分析了Si-Ti-Cr硅化物包覆的Nb-Hf合金样品在大气和真空条件下的高温热震性能。通过模拟在热冲击过程中涂层的温度场和热应力场分布,揭示了Si-Ti-Cr涂层在大气和真空条件下的热冲击失效机理。结果表明,在1300 ℃热震循环100次条件下,涂层的真空失重小于0.8 mg/cm²;在1600 ℃热震循环200次条件下,涂层的空气增重小于3 mg/cm²。硅化物涂层在1300 ℃真空环境下和1600 ℃空气环境下具有优异的抗热震性能。     

等离子喷涂和激光熔覆热障涂层隔热性能比较

采用多种方法制备不同类型的Al2O3-13％TiO2热障涂层,即等离子喷涂常规涂层、纳米结构涂层及激光熔覆纳米结构涂层．在分析三类涂层微观组织的基础上,对其隔热性能进行了比较．结果表明,即等离子喷涂常规陶瓷涂层呈典型的层状堆积特征,纳米结构涂层都为特殊的两相结构,其中部分熔化区由类似的残留纳米粒子组成,等离子喷涂纳米结构涂层的完全熔化区为片层状结构,而相应的激光熔覆涂层的完全熔化区则为细小等轴晶．在相同条件下,等离子喷涂纳米结构热障涂层具有最好的隔热性能,而激光熔覆纳米结构涂层的隔热性能要好于等离子喷涂常规涂层．     

Transmission electron microscopy observation of microstructure of plasma-sprayed nanostructured zirconia coating

Nanostructured zirconia coatings deposited by plasma spraying technique were observed using transmission electron microscopy (TEM). It was found that the as-sprayed nanostructured zirconia coating had bimodal microstructures in terms of grain size distribution in the direction parallel to substrate surface. One was in the range 30–120 nm, which was the dominative structure of the coating, and the other was about 150–400 nm. The cross-section micrograph of the plasma sprayed nanostructured zirconia coating revealed that the coating still exhibited lamellar structure with columnar grains extending through its thickness. In conjunction with partially molten zirconia grains, amorphous regions were found. Domain structure and superlattice structure were observed in the plasma-sprayed nanostructured zirconia coating. The formations of the domain and superlattice structures are discussed in this paper.     

大气等离子喷涂TiO2涂层性能及厚涂层制备工艺

为改善TiO2溅射靶材主要依赖进口的局面,采用大气等离子喷涂技术在不锈钢SUS304平板基体及管状基体上制备了TiO2涂层。利用扫描电子显微镜对涂层形貌进行了观察,并对涂层与基体的结合强度、涂层孔隙率及抗热震性能分别进行了表征。结果表明：粉末熔化及铺展良好,截面可见典型层状结构。涂层与基体以机械结合为主,断裂基本发生在基体与粘结层界面处;涂层的孔隙率较低,同时具有良好的抗热震性能。厚涂层制备过程中,采用循环水冷却方法对不锈钢SUS304管状基体进行冷却,涂层沉积速度快且无开裂和脱落,涂层厚度可达8 mm。通过对冷却装置的改进及喷涂工艺的进一步优化,有望在大尺度管状基体上制备厚涂层以满足溅射蒸镀辊的需要。     

Analysis of the Microstructure and Thermal Shock Resistance of Laser Glazed Nanostructured Zirconia TBCs

Nanostructured zirconia thermal barrier coatings (TBCs) have been prepared by atmospheric plasma spraying using the reconstituted nanosized yttria partially stabilized zirconia powder. Field emission scanning electron microscope was applied to examine the microstructure of the resulting TBCs. The results showed that the TBCs exhibited a unique, complex structure including nonmelted or partially melted nanosized particles and columnar grains. A CO₂ continuous wave laser beam has been applied to laser glaze the nanostructured zirconia TBCs. The effect of laser energy density on the microstructure and thermal shock resistance of the as-glazed coatings has been systematically investigated. SEM observation indicated that the microstructure of the as-glazed coatings was very different from the microstructure of the as-sprayed nanostructured TBCs. It changed from single columnar grain to a combination of columnar grains in the fracture surface and equiaxed grains on the surface with increasing laser energy density. Thermal shock resistance tests have showed that laser glazing can double the lifetime of TBCs. The failure of the as-glazed coatings was mainly due to the thermal stress caused by the thermal expansion coefficient mismatch between the ceramic coat and metallic substrate.