Multidisciplinary approach for investigating the hot corrosion behavior of thermal barrier coatings

Herein, we propose a new multidisciplinary approach for investigating the corrosion behavior of thermal barrier coatings, combining the thermal-gradient mechanical fatigue method with hot corrosion tests. Corrosive salts (Na₂SO₄; V₂O₅) of varying concentrations (10−20 mg/cm²) were deposited on the surface of yttria-stabilized zirconia (YSZ) coatings to evaluate the microstructural changes occurring during the reaction, via thermal graded mechanical fatigue tests. The tests were conducted at a surface temperature of 1150 °C in 10 min cycles and underwent applied uniaxial tensile loads. The corrosion tests show that the ZrV₂O₇ plays an important role as an intermediate in the collapse of the lamellar structures during the reaction, which results from the repetitive precipitation of V₂O₅ and m-ZrO₂ from the ZrV₂O₇. The microstructure of corroded YSZ coatings exhibited a different degradation mechanism under a thermomechanical environment, compared with the testing under isothermal atmospheric conditions.     

Competent F18 bioglass-Biosilicate® bone graft scaffold substitutes

Biosilicate® glass-ceramic (BioS) offers an attractive choice for the manufacturing of scaffolds because of their high bioactivity, non-toxicity, bactericidal activity and biodegradability. Despite these positive properties, Biosilicate® scaffolds that have been developed so far show low fracture strength, limiting their clinical application. For this reason, our aim was to increase their strength through vacuum infiltration of F18 bioactive glass. First, we calculated the maximum attainable theoretical compressive strength of a scaffold using the Ryshkewitch and Ashby-Gibson models. We show that for a total porosity of 80 %, σ₀ = 250 MPa, and n = 5 the compressive strength estimated by both models is approximately 4.5 MPa. Afterward, the Biosilicate scaffolds were prepared using the foam replica technique and recoated several times with a F18 glass slurry to eliminate surface defects. Scanning Electron Microscopy examination showed that the F18 indeed helped to remove surface defects and partially infiltrated the hollow struts, significantly increasing their mechanical integrity. The F18-BioS scaffolds exhibited a total porosity of 82 %, an average cell size of 525 μm, and compressive strength of 3.3 ± 0.3 MPa, which is close to the predicted value and significantly higher than those of sole BioS scaffolds of a similar structure (< 0.1 MPa). These values are within the range of commercial scaffolds based on Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), having a considerable advantage of being more osteoinductive, angiogenic, and highly bactericidal. The F18-BioS scaffolds developed in this work thus have high potential for odontology or craniofacial surgeries that do not involve high load–bearing conditions.     

Fatigue Delamination Characteristics of Plasma Sprayed Coatings under Fretting

FRETTING is referring to a reciprocating motion withthe small displacement between two components incontact[1].Fretting wear is superficial materialremoval during the fretting.It severely reduces theperformance,efficiency and service lifetime of thecomponents[2],Thermal spraying has been employedto enhance the fretting wear resistance of components,and the fretting wear behavior of the coatings has beenalso explored.However,the experimental results wereoften contradictive and confusing.On …     

黄原胶对消失模铸造涂料性能的影响

为提高消失模铸造水基涂料的质量,探讨了黄原胶作为微量添加剂对涂料性能的影响.试验研究表明,铸造涂料中加入适量的黄原胶可提高悬浮性、显著增大涂料粘度和涂挂性、改善涂料的流变行为.黄原胶还可显著提高涂层的强度,但使涂层透气性略有降低.鉴于黄原胶的优异性能,可望在消失模铸造水基涂料中获得应用.     

CVD与PVD硬涂层研究的进展

论述了用CVD和PVD方法制备硬涂层的若干进展，包括MT-CVD，PACVD，HVS及IBAD等，并介绍了超硬涂层发展的简况。     

车用空调器压缩机前端板铸件壳型铸造工艺实践

对前端板铸件壳型铸造中存在的铸造缺陷,采用优化浇注系统,对铁水进行二次孕育处理,调整碳当量控制在3.90%~4.15%,硅含量降低0.15%~0.20%,使产品抗拉强度≥270MPa,硬度(HB)为187~241,满足用户要求。     

大型宽厚板坯锻造工艺的探索

本文介绍了二重水压机车间仅用现有的设备、工装锻造最大达 6 0 0 0 mm×80 0 0 mm,厚度在 2 0 0 mm～ 5 0 0 mm板坯的工艺。其独特的筒体展伸工艺及体外锻造工艺开拓了小设备干大件的新路子 ,可供锻造行业的同仁们参考     

滚压成形力的数值计算与模拟

滚压成形技术在工程中的应用越来越广泛.但是到目前为止,滚压成型方面的理论还不完善,有些计算公式还有待验证.本文对板材进行U型成形时的成形力与成形角和板厚之间的关系进行了模拟数值计算和现场测量,并与经验公式的计算结果进行了比较,存在有较大的差异,从而说明经验计算公式有待进一步修正.     

反应等离子喷涂TiN/AlN涂层在润滑状态下摩擦磨损性能的研究

对用反应等离子喷涂法制备的TiN/AlN涂层在油润滑条件下的摩擦磨损特征进行了研究,并就轻、重载荷下的磨损机理进行了探讨。结果表明:油润滑条件下,涂层磨损体积显著降低。在轻载荷下,以疲劳磨损为主;在重载荷下,以脆性剥落和磨粒磨损为主。     

第三届中国国际压铸展览会侧记

介绍了第三届中国国际压铸展览会有关情况，根据展出现状对国内外压铸机、模具，涂料，压铸合金。熔化及保温炉等作了介绍和评述。