Fabrication of Multiple Oxidation-Resistant Coating on C/SiC Matrix

2010 ◽  
Vol 105-106 ◽  
pp. 406-408
Author(s):  
Yan Li Huo ◽  
Yu Feng Chen ◽  
Jie Tang ◽  
Hai Lin Liu ◽  
Chun Peng Wang
Keyword(s):  
High Speed ◽  
Middle Layer ◽  
Optical Microscope ◽  
Combustion Gas ◽  
Component Distribution ◽  
Good Oxidation Resistance ◽  
Eds Analysis ◽  
Gradient Component ◽  
Oxidation Resistant ◽  
Sic Composites

Oxidation-resistant coatings with gradient structures on C/SiC composites were fabricated. The gradient oxidation-resistant coatings were composed of three layers. The inner layer was reaction-bonded SiC which was fabricated by silicon infiltration. The middle layer was dense CVD SiC with the gradient component which was produced by the pyrolysis of methyltrichlorosilan (MTS) in excess hydrogen. The outer layer was a sealed layer with B4C and MoSi2 powders which was fabricated by slurry process. Optical microscope and SEM were used to observe the cross-section morphology and microstructure of coatings. XRD and EDS were used to characterize the phase composition and component distribution of coatings. EDS analysis showed the component distribution of CVD SiC coating changed significantly with the change of ratio of MTS to H2. The result indicated that C/SiC composite had good oxidation resistance when it was used at high temperature in the environment of high-speed combustion gas.

A correlation of CL emissions from Penrith sandstone with elemental distributions obtained by simultaneous SEM-CL and EDS analysis

1995 ◽  
Vol 53 ◽  
pp. 392-393
Author(s):  
Paul J. Wright
Keyword(s):  
Optical Microscope ◽  
Electron Gun ◽  
High Electron ◽  
Collection System ◽  
Electron Hole ◽  
Depositional Processes ◽  
Eds Analysis ◽  
Distribution Mapping ◽  
Backscattered Electron ◽  
Electron Imaging

Most industrial and academic geologists are familiar with the beautiful red and orange cathodoluminescence colours produced by carbonate minerals in an optical microscope with a cold cathode electron gun attached. The cement stratigraphies interpreted from colour photographs have been widely used to determine the post depositional processes which have modified sedimentary rock textures.However to study quartzose materials high electron densities and kV's are necessary to stimulate sufficient emission. A scanning electron microscope with an optical collection system and monochromator provides an adequate tool and gives the advantage of providing secondary and backscattered electron imaging as well as elemental analysis and distribution mapping via standard EDS/WDS facilities.It has been known that the incorporation of many elements modify the characteristics of the CL emissions from geological materials. They do this by taking up positions between the valence and conduction band thus providing sites to assist in the recombination of electron hole pairs.

scholarly journals Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Xiangjun Xu ◽  
Rui Hu ◽  
Junpin Lin ◽  
Jian Guo
Keyword(s):  
Mushy Zone ◽  
Solidification Rate ◽  
Solidus Temperature ◽  
Melting Zone ◽  
Optical Microscope ◽  
Directionally Solidified ◽  
Good Oxidation Resistance ◽  
Columnar Grains ◽  
Columnar Grain ◽  
Evolution Of Microstructure

High Nb-containing TiAl alloys have good oxidation resistance and mechanical properties, but the microstructure and the properties are substantially affected by the segregation. To quantitatively investigate the segregation behavior of Al during solidification, microstructures of directionally solidified (DS) Ti-45Al-8Nb (in atomic percent) alloy prepared at withdrawing rates of 30 μm/s and 200 μm/s and a temperature gradient of 4200 K/m were observed by optical microscope and electronic probe microanalyzer. The microsegregations were characterized by wave dispersive spectroscopy. The results show that the DS ingots include the no melting zone, directionally solidified zone with columnar grains, mushy zone, and quenched liquid zone. The primary dendritic arm spacings are 353 μm and 144 μm, respectively, for the two ingots. But the solidified microstructures of the ingots are large lamellar colonies, which contain a few B2 patches and γ bands induced by microsegregation. From dendritic zone to columnar zone, the volume fractions of B2 patches and γ bands decrease. The segregation extents of Al and Nb decrease with the increase of solidification rate. There exists an obvious back diffusion process of Al during solidification and cooling after solidification. According to evolution of Al concentration profiles from mushy zone to columnar grain zone, interdiffusion coefficient for Al in β-Ti at near solidus temperature is semiquantitatively calculated, and the value is (6 – 11) × 10−11 m2/s.

scholarly journals Pitting Corrosion of Natural Aged Al–Mg–Si Extrusion Profile

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1081 ◽  
Author(s):  
Quanmei Guan ◽  
Jing Sun ◽  
William Wang ◽  
Junfeng Gao ◽  
Chengxiong Zou ◽  
...  
Keyword(s):  
Pitting Corrosion ◽  
High Speed ◽  
Three Dimensional ◽  
Optical Microscope ◽  
Damage Initiation ◽  
Coarse Grains ◽  
Corrosion Risk ◽  
Heterogeneous Microstructures ◽  
Set Up ◽  
Pit Depth

With the quick development of the high-speed railway and the service of the China Railway High-speed (CRH) series for almost a decade, one of the greatest challenges is the management/maintenance of these trains in environmental conditions. It is critical to estimate pitting damage initiation and accumulation and set up a corresponding database in order to support the foundations for interactive corrosion risk management. In this work, the pitting corrosion of a nature-aged commercial 6005A-T6 aluminum extrusion profile for 200 days was studied comprehensively. The heterogeneous microstructures were conventionally identified by the in situ eddy current, suggesting which investigated regions to fabricate samples for. After constant immersion for 240 h in 3.5 wt % NaCl, the shapes and depths of the pits were captured and measured by optical microscope (OM) and three-dimensional optical profilometry (OP), providing detailed quantification of uniform pitting corrosion. The typical features of the pits dominated by the distribution of precipitates include the peripheral dissolution of the Al matrix, channeling corrosion, intergranular attack, and large pits in the grains. Due to the high density of continuous anodic and cathodic particles constituted by alloying elements in coarse grains, the number of pits in the coarse grains was the highest while the number in the fine grains was the lowest, indicating that fine grains have the best corrosion resistance. The experimental dataset of the pit depth integrated with its corresponding microstructure would set the benchmark for further modeling of the pit depth and the remaining ductility, in order to manage the damage tolerance of the materials.

Effect of Pre-Oxidation Treatment on the Thermal Shock Resistance of Thermal Barrier Coatings in a Combustion Gas Environment

2010 ◽  
Vol 654-656 ◽  
pp. 1924-1927 ◽  
Author(s):  
Hui Mei ◽  
Lai Fei Cheng ◽  
Ya Nan Liu ◽  
Li Tong Zhang
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Thermal Shock Resistance ◽  
High Speed ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Oxidation Treatment ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Shock Resistance

Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The TBC coating comprised of 92 wt.% ZrO2 and 8 wt.% Y2O3 (YSZ), CoNiCrAlY bond coat, and MarM247 nickel base super alloy. After APS of YSZ two batches of TBC specimens were tested, one batch of which was pre-oxidised in air for 10h at 1080 oC. Both types of the specimens were directly pushed into a combustion gas at 1150 oC for 25 min and then out to the natural air for quenching. The combustion gas was produced by burning jet fuel with high speed air in a high temperature wind tunnel, which simulates the real service conditions in an aeroengine. Results show that TBCs prepared by the APS had good thermal shock resistance in the combustion gas. The pre-oxidation treatment of the TBC had a significant effect on its thermal shock life. The as-oxidised TBCs always had worse thermal shock resistance than the as-sprayed ones after thermal shock cycles.

Fabrication and Properties of Cu-Cr Coatings on the Inner Wall of Steel Pipe by Mechanical Alloying Method

2012 ◽  
Vol 602-604 ◽  
pp. 1663-1666
Author(s):  
Zhong Qing Tian ◽  
Guo Xing Zhang ◽  
Wei Jiu Huang ◽  
Yu Kai Zhu
Keyword(s):  
Friction Coefficient ◽  
Mechanical Alloying ◽  
Coating Thickness ◽  
High Speed ◽  
Testing Machine ◽  
Optical Microscope ◽  
Steel Pipe ◽  
Rotating Speed ◽  
Friction Testing ◽  
Cr Coating

The mechanical alloying method process has been innovatively used to prepare Cu-Cr coating on the inner wall of steel pipe. The effect of the rotating speed on thickness, microhardness and friction coefficient of the Cu-Cr coating was investigated. The coating thickness was measured from all samples using optical microscope. The microhardness was analyzed by Digital Microhardness Tester. The friction coefficient was tested by high speed reciprocating friction testing machine. The results show that the coating thickness is 26, 29 and 31μm at the rotating speed of 200, 250 and 300 rpm. The microhardness of the Cu-Cr coating prepared at 200, 250 and 300 rpm are about 760, 780 and 830 Hv. The friction coefficient of the Cu-Cr coating prepared at 200 rpm are about 0.25, 0.40 and 0.38 at the frequencies of 3, 4 and 5 Hz. The friction coefficient of the Cu-Cr coating prepared at 250 rpm are about 0.30, 0.29 and 0.20 at the frequencies of 3, 4 and 5 Hz. The friction coefficient of the Cu-Cr coating prepared at 300 rpm are about 0.10, 0.13 and 0.09 at the frequencies of 3, 4 and 5 Hz.

The Cutting Speed Influences on Tool Wear of ZTA Ceramic Cutting Tools and Surface Roughness of Work Material Stainless Steel 316L during High Speed Machining

2016 ◽  
Vol 840 ◽  
pp. 315-320 ◽  
Author(s):  
Afifah Mohd Ali ◽  
Norazharuddin Shah Abdullah ◽  
Manimaran Ratnam ◽  
Zainal Arifin Ahmad
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Tool Wear ◽  
High Speed ◽  
Dense Body ◽  
Cutting Speed ◽  
Optical Microscope ◽  
Stainless Steel 316L ◽  
Crater Wear ◽  
Matlab Programming

The purpose of this research is to find the effects of cutting speed on the performance of the ZTA ceramic cutting tool. Three types of ZTA tools used in this study which are ZTA-MgO(micro), ZTA-MgO(nano) and ZTA-MgO-CeO2. Each of them were fabricated by wet mixing the materials, then dried at 100°C before crushed into powder. The powder was pressed into rhombic shape and sintered at 1600°C at 4 hours soaking time to yield dense body. To study the effect of the cutting speed on fabricated tool, machining was performed on the stainless steel 316L at 1500 to 2000 rpm cutting speed. Surface roughness of workpiece was measured and the tool wears were analysed by using optical microscope and Matlab programming where two types of wear measured i.e. nose wear and crater wear. Result shows that by increasing the cutting speed, the nose wear and crater wear increased due to high abrasion. However, surface roughness decreased due to temperature rise causing easier chip formation leaving a good quality surface although the tool wear is increased.

On the Feasibility of Nuclear Versus Combustion Gas Turbine Propulsion for High-Speed Cargo Ships

2004 ◽  
Author(s):  
H. Boonstra ◽  
A. C. Groot ◽  
C. A. Prins
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Gas Turbine ◽  
High Speed ◽  
Nuclear Power ◽  
Parametric Design ◽  
Pebble Bed ◽  
Pressurized Water ◽  
Combustion Gas ◽  
The Impact

This paper presents the outcome of a study on the feasibility of a nuclear powered High-Speed Pentamaran, initiated by Nigel Gee and Associates and the Delft University of Technology. It explores the competitiveness of a nuclear power plant for the critical characteristics of a marine propulsion plant. Three nuclear reactor types are selected: the Pressurized Water Reactor (PWR), the Pebble-bed and Prismatic-block HTGR. Their characteristics are estimated for a power range from 100 MWth to 1000 MWth in a parametric design, providing a level base for comparison with conventional gas turbine technology. The reactor scaling is based on reference reactors with an emphasis on marine application. This implies that preference is given to passive safety and simplicity, as they are key-factors for a marine power plant. A case study for a 60-knot Pentamaran shows the impact of a nuclear power plant on a ship designed with combustion gas turbine propulsion. The Prismatic-block HTGR is chosen as most suitable because of its low weight compared to the PWR, in spite of the proven technology of a PWR. The Pebble-bed HTGR is considered too voluminous for High-Speed craft. Conservative data and priority to simple systems and high safety leads to an unfavorable high weight of the nuclear plant in competition with the original gas turbine driven Pentamaran. The nuclear powered ship has some clear advantages at high sailing ranges.

A Study of Developing Composite Material of Penetrated Diamond Particles Into Metal Plate

2009 ◽  
Author(s):  
Keijiro Nishi ◽  
Shigeru Tanaka ◽  
Shigeru Itoh
Keyword(s):  
Thermal Conductivity ◽  
Shock Wave ◽  
Composite Material ◽  
High Speed ◽  
High Hardness ◽  
Optical Microscope ◽  
Metal Plate ◽  
Underwater Shock Wave ◽  
Diamond Particles ◽  
Underwater Shock

An explosive welding technique which uses underwater shock wave to weld thin aluminum plate has been studied and the technical advantages were reported. In this research, we propose a method to produce a composite material using an underwater shock wave generated by detonation of explosive. In the production process, a metal plate (flyer plate) accelerates to a high speed by the underwater shock wave, and collided with diamond particles and penetrated the metal plate. Diamonds were used as the particles and aluminum plates (A1050) as the flyer plates. Diamond has high hardness and excellent thermal conductivity, therefore diamond should provide improvement in the thermal conductivity of the composite material. From recovered sample, the multilayer joined surface including diamond particles was observed using an optical microscope. The production of the pipe of composite materials was attempted using this technique as the application. Details of the experimental methods and results are reported in this paper.

Natural Aging Behavior of Double-Sided MIG Welded A7N01-T5 Aluminum Alloy

2018 ◽  
Vol 941 ◽  
pp. 1155-1160
Author(s):  
Ying Li ◽  
Zhi Qiang Zhang ◽  
Jian Liu ◽  
Hua Yin ◽  
Chang Shu He
Keyword(s):  
Aluminum Alloy ◽  
High Speed ◽  
Aging Process ◽  
Weld Zone ◽  
Natural Aging ◽  
Middle Layer ◽  
Age Hardening ◽  
Aging Behavior ◽  
Epma Analysis ◽  
Zn Content

A heat treatable A7N01 (Al-Zn-Mg) aluminum alloy mainly used to fabricate high-speed train body structures was double-sided welded by MIG welding. The natural aging behavior of the joint was systematically studied by local and global mechanical property testing method. Based on TEM observation and EPMA analysis, the key factors that lead to different natural aging behavior among various regions of the joint were discussed. The global tensile strength of the joints increased obviously after natural aging. All the joint samples fractured in the weld zone, which demonstrated the weld zone was the weakest zone of the joints. And the strength of the global welds were depended on the microstructure and natural aging ability of the weld zone. Moreover, the increase of the tensile property of the three local regions in the weld zone after post natural aging decreased as Middle>lower>upper. The above phenomenon was also further confirmed by microhardness measurement. The age hardening behavior is greatly influenced by the concentration of strengthening precipitates forming element Zn. The Zn content in the weld zone determined by EPMA showed that element Zn was dispersed unevenly, which is attributed to the double V-groove design used in this work and Zn vaporization in the molten pool during welding. The Zn content in the middle layer metals is higher than that of the upper and lower layers, resulting in the remarkable hardening response for the middle layer of the weld zone during natural aging process. Additionally, the solution zone containing the same Zn content as the base metal and undergoing sufficient solid solution during welding was found to possess the high hardening ability after natural aging process.

Ultra High Speed Turning of Inconel 718 with Sialon Ceramic Tools

2010 ◽  
Vol 126-128 ◽  
pp. 653-657 ◽  
Author(s):  
Guang Ming Zheng ◽  
Jun Zhao ◽  
Xin Yu Song ◽  
Cao Qing Yan ◽  
Yue En Li
Keyword(s):  
Wear Mechanisms ◽  
Inconel 718 ◽  
High Speed ◽  
Cutting Speed ◽  
Optical Microscope ◽  
Cutting Condition ◽  
Inconel 718 Alloy ◽  
High Speed Turning ◽  
Sialon Ceramic ◽  
Ultra High Speed

This paper explores the wear mechanisms of a Sialon ceramic tool in ultra high speed turning of Nickel-based alloy Inconel 718. Microstructures of the chips are also investigated. Stereo optical microscope and scanning electron microscope (SEM) are employed to observe worn surfaces of the tool produced by various wear mechanisms and morphological features of chips. In addition, the elemental compositions of wear products are evaluated by energy-dispersive X-ray spectroscopy (EDS). As a result of the study, wear mechanisms identified in the machining tests involve adhesive wear and abrasive wear. At the initial stage of cutting process, crater wear and flank wear are the main wear patterns. At the rapid wear stage, the SEM and EDS results showed that the adhered elements of Inconel 718 alloy on the tool rake face such as Ni, Fe and Cr accelerated the tool wear rate. Meanwhile, it was found that the chip morphology was serrated type under ultra high speed cutting condition, furthermore, the tendency of serration of the chip increased with the increase in cutting speed and feed rate.

Sign in / Sign up

Export Citation Format

Share Document