Microstructure and Oxidation Resistance of Y Modified Silicide Coatings Prepared on Zr-Ti-Al Alloy

2018 ◽  
Vol 913 ◽  
pp. 365-374
Author(s):  
Jia Hua He ◽  
Xi Ping Guo
Keyword(s):  
Growth Rate ◽  
Layer Structure ◽  
Deposition Process ◽  
Al Alloy ◽  
Silicide Coating ◽  
Arc Melting ◽  
Double Layer Structure ◽  
Oxidation Resistant ◽  
Induction Skull Melting ◽  
High Frequency Induction

Zr-20Ti-5Al (at. %) alloy used as substrates for Si-Y2O3co-deposition experiments was prepared by firstly vacuum non-consumable arc melting and then high frequency induction skull melting. The results showed that Y modified silicide coating prepared at 1250 °C for 4 h possessed a double-layer structure, mainly consisting of a thick (Zr, Ti)Si2outer layer and a 15 mm thick (Zr, Ti)Si inner layer. Meanwhile, the growth rate of ZrSi2phase changed with temperature, while the growth rate of ZrSi did not vary significantly with temperature. The growth of the coating as well as the two layers followed parabolic laws, and the co-deposition process was controlled by diffusion. ZrSi2was not appropriate as oxidation-resistant coatings to protect Nb based alloy from oxidation due to the lack of the formation of good quality glassy SiO2layer in the scale.

Microstructure and High-Temperature Oxidation-Resistant Performance of Several Silicide Coatings on Nb-Ti-Si Based Alloy Prepared by Pack Cementation Process

2012 ◽  
Vol 533 ◽  
pp. 145-165
Author(s):  
Jing Li ◽  
Xi Ping Guo
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Outer Layer ◽  
High Temperature Oxidation ◽  
Layer Structure ◽  
Middle Layer ◽  
Alloy Coating ◽  
Deposition Process ◽  
Temperature Oxidation ◽  
Oxidation Resistant

The microstructure and high-temperature oxidation-resistant performance of several silicide coatings on an Nb-Ti-Si based alloy were revealed in the present work. These silicide coatings were prepared respectively at 1250°C for 8 h by pack siliconizing process, Si-Y co-deposition process and Si-Al-Y co-deposition process (with different Al contents in the packs). The results showed that the purely siliconized coating was composed of a (Ti,Nb)5Si3 ouer layer, a (Nb,X)Si2 (X represents Ti, Cr and Hf elements) middle layer and a (Ti,Nb)5Si4 inner layer. A thicker and more compact double-layer structure including a (Nb,X)Si2 outer layer and a (Ti,Nb)5Si4 inner layer was observed in the Si-Y co-deposition coating. In addition, a higher Y content (about 0.34 at. %) in the outer layer of the Si-Y co-deposition coating was obtained, while the Y content was only about 0.06 at. % in the purely siliconized coating. The Si-Al-Y co-deposition coating possessed a (Nb,X)Si2 outer layer, a (Ti,Nb)5Si4 middle layer and an Al, Cr-rich inner layer. A suitable addition of Al powders (5 wt. %) in the packs was beneficial to thicken the (Nb,X)Si2 outer layer, while a sharp reduction in the coating thickness was found when excess Al powders (10 wt. %) was added in the packs. However, compared with the former coating, the later coating prepared with more Al powders in the packs resulted in a slight increase in the content of Al and Y in the (Nb,X)Si2 outer layer from about 0.21 and 0.54 at. % to 0.87 and 0.79 at. % respectively. The thickness and microstructure of the scales formed on above four coatings upon oxidation at 1250°C for either 5 h or 100 h were comparatively investigated. The oxidation resistance of these silicide-type coatings was notably enhanced by the addition of Y and Al. The Si-Al-Y co-deposition coating, which was prepared with 5 wt. % Al powders in the pack, possessed the best oxidation resistance due to its optimum dense and continuous scale and compact coating remained. Keywords: Nb-Ti-Si based alloy; coating; microstructure; oxidation-resistant perfor-mance *Corresponding author. Tel./fax: +86 29 88494873. E-mail address: [email protected] (X. Guo).

Oxidation Behavior and Pack Siliconized Oxidation-Resistant Coatings of an Nb-Based Ultrahigh Temperature Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 371-374 ◽  
Author(s):  
X.P. Guo ◽  
L.X. Zhao ◽  
Ping Guan ◽  
K. Kusabiraki
Keyword(s):  
Oxidation Resistance ◽  
Double Layer ◽  
Outer Layer ◽  
Oxidation Behavior ◽  
Layer Structure ◽  
Transitional Layer ◽  
Double Layer Structure ◽  
Oxidation Resistant ◽  
Ultrahigh Temperature ◽  
Two Phases

The halide-activated pack cementation method was utilized to deposit silicide coatings on a multicomponent Nb-Ti-Si based alloy. The siliconized temperature was 1150 °C and the holding time was 10h. Both the specimens with siliconized coatings and without coatings were oxidized at 1250°C for 5, 10, 20, 50 and 100h respectively. The coating possessed a double layer structure with the composition of (Nb,X)Si2 (X represents Ti, Cr and Hf), and the outer layer was denser. The major structure in the outer layer was composed of columnar crystals perpendicular to the interface between the coating and the substrate, and that in the inner layer was mainly composed of equiaxed crystals. A transitional layer about 5μm thick was found between the coating and the substrate. After oxidation at 1250°C, the major constituents in the scale were SiO2 and TiO2 and the mole ratio of these two phases was about 2:1. The thickness of the (Nb,X)Si2 layer decreased and that of transitional layer increased as the oxidation time prolonged. The siliconized coating exhibited excellent oxidation-resistance at 1250°C within 50 hours.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

High growth-rate atomic layer deposition process of cerium oxide thin film for solid oxide fuel cell

2019 ◽  
Vol 45 (3) ◽  
pp. 3811-3815 ◽  
Author(s):  
Jin-Geun Yu ◽  
Byung Chan Yang ◽  
Jeong Woo Shin ◽  
Sungje Lee ◽  
Seongkook Oh ◽  
...  
Keyword(s):  
Thin Film ◽  
Growth Rate ◽  
High Growth ◽  
Atomic Layer ◽  
Deposition Process ◽  
High Growth Rate ◽  
Solid Oxide ◽  
Oxide Thin Film ◽  
Oxide Fuel ◽  
Layer Deposition

Effects of Cr+ ion implantation on the oxidation of Ni3Al

1993 ◽  
Vol 8 (4) ◽  
pp. 734-740 ◽  
Author(s):  
M. Chen ◽  
S. Patu ◽  
J.N. Shen ◽  
C.X. Shi
Keyword(s):  
Oxidation Resistance ◽  
Layer Structure ◽  
Surface Region ◽  
Optical Microscope ◽  
Al Alloy ◽  
Temperature Oxidation ◽  
Intermediate Layers ◽  
Air Interface ◽  
Before And After ◽  
High Temperature Oxidation Behavior

Ni3Al samples were implanted with different doses of 150 keV Cr+ ions to modify the surface region. The high temperature oxidation behavior was tested. The surface layer structure was investigated by AES, TEM, XRD, and optical microscope before and after the test. The experimental results show that chromium ions turn a small amount of ordered superlattice Ni3Al phase into a disordered Ni–Al–Cr phase. Also there is a bcc chromium phase in the implanted sample. Implanted Ni3Al alloy has better oxidation resistance than the unimplanted one at 900 °C. The oxide layer is of a multilayer structure after 50 h oxidation, composed of a NiO inner layer, Cr2O3, spinel NiAl2O4 intermediate layers, and an α–Al2O3 external layer at the oxide/air interface. The α-Al2O3 and Cr2O3 are independent scale-like layers. The two protective layers improve the oxidation resistance significantly. The effects of implanted elements and possible reaction mechanisms are discussed.

Reaction between MgO-SiO2 refractory material and Fe-Al alloy

2018 ◽  
Vol 115 (5) ◽  
pp. 512 ◽  
Author(s):  
Abdulaziz Alhussein ◽  
Piotr R. Scheller ◽  
Wen Yang
Keyword(s):  
Refractory Material ◽  
Reaction Rate ◽  
Interface Layer ◽  
Al Alloy ◽  
Single Particles ◽  
Spinel Layer ◽  
Reduction Of Iron ◽  
Rate Controlling Step ◽  
High Frequency Induction Furnace ◽  
High Frequency Induction

The interaction between molten Fe-Al alloy containing 5.1 wt.% aluminium and MgO-SiO2-based refractory was investigated. In high-frequency induction furnace at 1550 °C refractory samples were immersed in liquid alloy for 1 min, 2 min, 10 min, 20 min, 30 min and 60 min. Scanning electron microscope was employed to investigate phases at the interface and inclusions in the Fe-Al alloy. Forsterite phase in refractory was transformed to MgO·Al2O3 spinel, owing to the reduction of iron oxide and silica in forsterite by aluminium in the Fe-Al alloy at the interface. The interface layer separated locally from the refractory material and formed cluster and single particles in the Fe-Al alloy. In view on the reaction rate, the disintegration of the refractory material increased the reaction area but interfered with increasing thickness of the spinel layer. The dissolution rate of silica into the molten alloy decreased with increasing the reaction time because of the slowed down transport of aluminium diffusing through increasing spinel layer became the rate controlling step.

Properties and CA4GE-Engine Test of TiAl-Based Alloy Valves by Permanent Mold Casting

2010 ◽  
Vol 139-141 ◽  
pp. 557-560
Author(s):  
Wen Bin Sheng ◽  
Chun Xue Ma ◽  
Wan Li Gu
Keyword(s):  
Tial Alloy ◽  
Centrifugal Casting ◽  
Casting Process ◽  
Vacuum Arc ◽  
Permanent Mold ◽  
Casting Method ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Mold Casting ◽  
Induction Skull Melting

TiAl-based alloy valves were manufactured by combining charges compressed /vacuum arc melting (VA)/ induction skull melting (ISM) procedure with permanent mold centrifugal casting method. Microstructures, compositions and mechanical properties of as-cast and hot isostatical pressed (HIPed) valves are detected. Results show that the permanent mold centrifugal casting process obviously refines the size of grain in TiAl alloy and the tensile strength of as-cast and HIPed valves are 550MPa and 580MPa at 20°C, 370MPa and 470MPa at 815°C, respectively. As-cast specimens show ~0% elongation at 20°C and 1~2% at 815°C, while HIPed ones show an elongation of 1~2% at room temperature and about 10% at 815°C. Furthermore, a 200-hour test was carried out with CA4GE-engine, which demonstrated the possibility of as-cast TiAl alloy valves for the substitution of present steel ones.

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