scholarly journals Tin Addition to Improve the Oxidation Behaviour of NbSs/Nb5Si3 Based In Situ Composite

2011 ◽  
Vol 278 ◽  
pp. 575-580 ◽  
Author(s):  
Stephane Knittel ◽  
Stéphane Mathieu ◽  
Michel Vilasi
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Oxidation Resistance ◽  
Oxidation Behaviour ◽  
Oxide Scales ◽  
Niobium Solid Solution

This work focuses on the effect of tin additions (2, 5 and 8%) to the MASC alloy (Nb-25Ti-8Hf-2Cr-2Al-18Si) on the microstructure and the oxidation behaviour at 815°C in air. The alloys are mainly constituted of a niobium solid solution plus the () Nb5Si3 silicides. For the higher Sn additions (5 and 8%), a fourth phase is evidenced: it is enriched in Sn and has a crystal structure close to Nb3Sn. The oxidation resistance of these alloys is clearly improved by tin additions: the oxygen inward diffusion is hindered and consequently the fragmentation of the silicides is avoided. Cracks in silicides are no longer observed for the MASC containing 8%Sn. This effect is not attributed to a better efficiency of the oxide scales but rather to the reduction of the niobium solid solution fraction with tin additions.

The Effect of Ge and Ti Additions on the Microstructures and Properties of Nb-18Si Based Alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
Zifu Li ◽  
Panos Tsakiropoulos
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Oxidation Resistance ◽  
Cast Alloy ◽  
High Volume ◽  
Primary Phase ◽  
Oxidation Behaviour ◽  
Volume Fractions ◽  
Two Phases ◽  
Cast Microstructure

ABSTRACTThe effects of Ge and Ti additions on the microstructure, hardness and oxidation behaviour of the alloys Nb–18Si–5Ge (ZF1) and Nb–24Ti–18Si–5Ge (ZF3) were studied. The as cast microstructure of the alloy ZF1 consisted of Nbss (cI2), and βNb5Si3 (tI32) with the latter being the primary phase and the two phases forming high volume fractions of Nbss + βNb5Si3 eutectic. The Ge addition stabilised the βNb5Si3 (tI32), and destabilised the Nb3Si (tP32) and the Nbss + Nb3Si eutectic. After heat treatment at 1200 °C for 100 h the βNb5Si3 (tI32) was partially transformed to the αNb5Si3 (tI32), and equilibrium was reached after heat treatment at 1500 °C for 100 h. The phases present in the as cast alloy ZF3 were the Nbss (cI2), and the Nb3Si (tP32), βNb5Si3 (tI32) and Ti5Si3 (hP16) silicides, with the latter forming a eutectic with the solid solution. The same phases were present after heat treatment at 1200 °C for 100 h but only the Nbss, and the Nb3Si and Nb5Si3 silicides were present after 100 h at 1500 °C where TiO2 was also formed. The Ge addition increased the microhardness of the Nb5Si3. The synergy of Ti with Ge resulted in a strong hardening effect and a remarkable retention of the hardness of the alloy ZF3. The additions of Ge and Ti to the Nb-18Si alloy improved the oxidation resistance at 800 °C, but pest oxidation behaviour was not eliminated.

Preparation and Oxidation Behaviour of an Al-Si Coating on a Ni3Al Based Single Crystal Superalloy IC21

2013 ◽  
Vol 747-748 ◽  
pp. 575-581 ◽  
Author(s):  
Yu Zhuo Liu ◽  
Qiong Wu ◽  
Shu Suo Li ◽  
Yue Ma ◽  
Sheng Kai Gong
Keyword(s):  
Phase Transformation ◽  
Oxidation Resistance ◽  
Outer Layer ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Oxidation Behaviour ◽  
Oxide Scales ◽  
Outward Diffusion ◽  
Microstructure Change ◽  
Β Phase

An Al-Si coating was prepared on IC21 alloy by powder pack cementation. The cyclic oxidation tests were carried out at 1150 in air for up to 100 h. The results indicate that the oxidation resistance of IC21 alloy is significantly improved by the Al-Si coating due to the presence of Ni2Al3and β-NiAl enriched outer layer, and Si can effectively supress the outward diffusion of Mo. The oxide scales mainly consist of α-Al2O3, which is the favorite to the oxidation resistance. Phase transformation occurred from β-NiAl to γ-Ni3Al and γ-Ni in the coating during oxidation. The coating still remained a certain amount of β phase after oxidation for 100h, which indicate a good protection. The microstructure change evolution was characterized, and the oxidation behavior of the coating was discussed.

Oxidation of Nb/Nb5Si3 In Situ Composites Fabricated via Spark Plasma Sintering with Al Addition

2013 ◽  
Vol 376 ◽  
pp. 49-53 ◽  
Author(s):  
Wen Yuan Long ◽  
Xiang Yan Zou ◽  
Wei Dong Wang ◽  
Jun Ping Yao
Keyword(s):  
Oxidation Resistance ◽  
Spark Plasma Sintering ◽  
Raw Materials ◽  
Oxidation Behaviour ◽  
X Ray Diffraction ◽  
In Situ Composites ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Al Addition

Dense Nb/Nb5Si3composites were fabricated via spark plasma sintering technology using Nb, Si, and Al elemental powders as raw materials. The microstructures of the synthesised composites were analysed through scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. The results show that the composites consisted of residual Nb particle phase and Nb5Si3phase. The microstructure of the Nb/ Nb5Si3in situ composites was evidently affected by Al addition, which prompted the formation of the Al3Nb10Si3phase. The oxidation resistance of the Nb/Nb5Si3in situ composites significantly improved with the increase in Al addition. Pesting oxidation behaviour was exhibited at 800°C by the Nb-20Si composites when exposed to air for 4h. This pest oxidation behaviour is not exhibited by the Nb-20Si-10Al and Nb-20Si-15Al composites after exposure to air for ~10h. The composite exhibits the best oxidation resistance at 15at% Al.

Effect of Nanocrystalline and Ti Implantation on the Oxidation Behaviour of Fe80Cr20 Alloy and Commercial Ferritic Steel

2011 ◽  
Vol 474-476 ◽  
pp. 2134-2139 ◽  
Author(s):  
Darwin Sebayang ◽  
Deni S. Khaerudini ◽  
Hendi Saryanto ◽  
M.A. Othman ◽  
T. Sujitno ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Crystallite Size ◽  
Oxidation Resistance ◽  
Oxidation Kinetics ◽  
Ferritic Steel ◽  
Oxidation Behaviour ◽  
Oxide Scales ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electronic Microscope

The oxidation behaviour of developed Fe80Cr20 alloy and commercial ferritic steel at 1173 - 1373 K in air is studied. Effects of crystallite size and titanium implantation on the oxidation behaviour of specimens were analyzed based on oxide morphologies and microstructures. Oxide scales characterisations of specimen after oxidized were identified by X-ray diffraction (XRD). The surface morphology of oxide scales were examined with scanning electronic microscope (SEM) and energy dispersive X-ray analysis (EDX). The rate constant of oxidation were determined using Wagner method. The results show that crystallite size and titanium implantation has remarkably enhanced the oxidation resistance. The oxidation kinetics indicate that the developed Fe80Cr20 as the finer crystallite size both unimplanted and implanted specimens show better performance.

scholarly journals Effect of Cr and Al alloying on the oxidation resistance of a Ti5Si3-incorporated MoSiBTiC alloy

2021 ◽  
Vol 40 (1) ◽  
pp. 204-213
Author(s):  
Xi Nan ◽  
Tomotaka Hatakeyama ◽  
Shuntaro Ida ◽  
Nobuaki Sekido ◽  
Kyosuke Yoshimi
Keyword(s):  
Solid Solution ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Oxidation Behavior ◽  
Oxide Scales ◽  
Accelerated Oxidation ◽  
Oxidation Test ◽  
Poor Oxidation Resistance

Abstract The effects of adding Cr and Al on the oxidation behavior of a Ti5Si3-incorporated MoSiBTiC alloy (46Mo–28Ti–14Si–6C–6B, at%) were investigated at 800 and 1,100°C. The addition of Cr and Al largely improved the oxidation resistance of the MoSiBTiC alloy at 800°C due to the formation of Cr2(MoO4)3 and Al2(MoO4)3 in the oxide scales. These protective molybdates mainly formed on the molybdenum solid solution (Moss) and Mo3Si phases that show poor oxidation resistance in the Cr- and Al-free alloy and consequently increased the oxidation resistance of the alloys. However, accelerated oxidation occurred on the 10Al alloy after the long-term oxidation test, suggesting that the formed oxide scale has limited protection ability. At 1,100°C, the addition of Cr and Al also enhanced the oxidation resistance to some extent by forming Cr2O3 and Al2O3 in the oxide scales.

Effect of Isothermal Forging on Microstructures and Mechanical Properties of Nb-Si In Situ Composite

2007 ◽  
Vol 561-565 ◽  
pp. 423-426 ◽  
Author(s):  
Yong Wang Kang ◽  
Shi Yu Qu ◽  
Ya Fang Han ◽  
Ji Xia Song ◽  
Ding Zhong Tang
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Nominal Composition ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
In Situ Composite ◽  
Large Size ◽  
Directional Texture ◽  
Niobium Solid Solution

Nb-Si based in-situ composites have great potential for the application of high temperature structure components. In this paper, the influence of microstructure on the compression behavior of Nb-Si in-situ composite forged at high temperature was studied. The alloy with nominal composition of Nb-12Si-24Ti-4Cr-4Al-2Hf was consumable arc-melted, and then isothermal forged at 960°C. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to characterize the microstructure, composition and phases. The compressive behaviors at 1250°C were carried out by Gleeble thermo-mechanical simulator. The results showed that the microstructures were inhomogenous in the different sections of the ingot, and no evident directional texture formed, and the main phases were niobium solid solution, Nb5Si3 and Ti5Si3. However, no macro-elements segregation in the ingot was observed. The compression strength was in the range of 140-360MPa. BSE observation showed that irregular-shaped Nb5Si3 and Ti5Si3 phases distributed in Nb solid solution and the size of Nb5Si3 in three tested samples was 10μm. Large size of eutectoid texture existed in the sample with strength of ~140MPa. On the contrary, in the sample with higher strength of 360MPa, eutectoid structures were hardly detected. The results suggested that the strength decreased gradually with size increase of eutectoid structure.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

PYROMET 538

Alloy Digest ◽  
1970 ◽  
Vol 19 (12) ◽  
Keyword(s):  
Solid Solution ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Oxidation Resistance ◽  
Heat Treating ◽  
Temperature Performance ◽  
Technology Corporation ◽  
Carpenter Technology Corporation

Abstract PYROMET 538 is a solid-solution strengthened, austenitic alloy with a desirable combination of strength, corrosion resistance, oxidation resistance, and economy. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-247. Producer or source: Carpenter Technology Corporation.

scholarly journals Oxidation behavior of non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution powders in air

2021 ◽  
Author(s):  
Huilin Lun ◽  
Yi Zeng ◽  
Xiang Xiong ◽  
Ziming Ye ◽  
Zhongwei Zhang ◽  
...  
Keyword(s):  
Solid Solution ◽  
Oxidation Resistance ◽  
Oxidation Behavior ◽  
Group Iv ◽  
Hypersonic Vehicles ◽  
Metal Carbides ◽  
Initial Oxidation ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Kinetics Of

AbstractMulti-component solid solutions with non-stoichiometric compositions are characteristics of ultra-high temperature carbides as promising materials for hypersonic vehicles. However, for group IV transition-metal carbides, the oxidation behavior of multi-component non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution has not been clarified yet. The present work fabricated four kinds of (Zr,Hf,Ti)Cx carbide solid solution powders by free-pressureless spark plasma sintering to investigate the oxidation behavior of (Zr,Hf,Ti)Cx in air. The effects of metallic atom composition on oxidation resistance were examined. The results indicate that the oxidation kinetics of (Zr,Hf,Ti)Cx are composition dependent. A high Hf content in (Zr,Hf,Ti)Cx was beneficial to form an amorphous Zr-Hf-Ti-C-O oxycarbide layer as an oxygen barrier to enhance the initial oxidation resistance. Meanwhile, an equiatomic ratio of metallic atoms reduced the growth rate of (Zr,Hf,Ti)O2 oxide, increasing its phase stability at high temperatures, which improved the oxidation activation energy of (Zr, Hf, Ti)Cx.

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