Oxidation Resistance and Mechanical Enhancement of Ferro-Silicon Nitride on Silica Sol Bonded SiC Castable

2018 ◽  
Vol 768 ◽  
pp. 286-290
Author(s):  
Ding Chen ◽  
Hua Zhi Gu ◽  
Ao Huang
Keyword(s):  
Silicon Nitride ◽  
Oxidation Resistance ◽  
Oxidation Rate ◽  
Microstructural Analysis ◽  
Isothermal Oxidation ◽  
Silica Sol ◽  
Damage Resistance ◽  
Sic Whiskers ◽  
Stress Damage ◽  
Ferro Silicon

Silica sol bonded SiC castable have obvious advantages of slag resistance and thermal stress damage resistance. However, they are not widely used due to their weak oxidation resistance at high temperature. Ferro-silicon nitride is added to improve the oxidation resistance of SiC castable. The efficiency of SiC castable in the presence of different contents of ferro-silicon nitride was evaluated through sintered properties, isothermal oxidation behaviors and microstructural analysis. The results show that sample with 5wt% ferro-silicon nitride possessed good mechanical behavior after heat treatment due to its acceleration for the formation of SiC whiskers. At 1500 °C, Isothermal oxdation curve indicated that the oxidation progress performed two-stage model controlled by chemical reaction at the earlier period and diffusion at the later period. Sample with 5wt% ferro-silicon nitride present faster oxidation rate (kc) at the earlier stage versus the contrast sample (0.025 mg·cm-2·min-1 vs 0.087 mg·cm-2·min-1), and slower oxidation rate (kd) at the later stage (0.145 mg·cm-2·min-1 vs 0.137 mg·cm-2·min-1). After 470 min isothermal oxidation test, the weigh gain of sample with 0 wt% ferro-silicon nitride exceeded the sample with 5wt% ferro-silicon nitride.

Effect of Cation Extraction on the Oxidation Resistance of Si3N4

2007 ◽  
Vol 280-283 ◽  
pp. 1263-1266
Author(s):  
Jian Qing Wu ◽  
Fang Li Yuan ◽  
Xin Jun Zeng ◽  
Ping Gen Rao
Keyword(s):  
Silicon Nitride ◽  
Oxidation Resistance ◽  
Oxidation Rate ◽  
Extraction Process ◽  
Extraction Temperature ◽  
Temperature Oxidation ◽  
Nitride Ceramics ◽  
Si3n4 Ceramics ◽  
Cation Extraction

A new method called cation extraction process has been applied to improve the oxidation resistance of silicon nitride ceramics with sintering additives. It is found that the high temperature oxidation rate of the Si3N4 ceramic treated by the process decreased remarkably in contrast to the oxidation rate of the Si3N4 without the process. The oxidation rate of Si3N4 ceramics with the cation extraction process is reduced more than 50% comparing with that of the Si3N4 ceramics without the process. The morphological characteristic and phase composition of the oxides were analyzed by means of SEM and XRD. The oxidation rate of silicon nitride after cation extraction treatment is determined by the quality of the “purified layer” formed below the pre-oxide scale. Thicker oxide layer formed in pre-oxidation, higher extraction temperature and longer extraction time are helpful to form a good “purified layer”.

Effect of the Amorphous Silica Coating Derived by Sol-Gel Processing on the Oxidation Behavior of Ni

2009 ◽  
Vol 79-82 ◽  
pp. 671-674
Author(s):  
B.Y. Ren ◽  
Y.H. Gao ◽  
S.J. Wang ◽  
X.J. Zhang ◽  
N.X. Feng
Keyword(s):  
Thin Film ◽  
Amorphous Silica ◽  
Oxidation Rate ◽  
Oxidation Behavior ◽  
Sol Gel ◽  
Silica Coating ◽  
Isothermal Oxidation ◽  
Dip Coating ◽  
Silica Sol ◽  
Gel Processing

Amorphous silica coating was deposited on the surface of Ni by dip-coating processing from commercial silica sol. Isothermal oxidation of the coated and uncoated specimens at 973 K to 1173 K in air was conducted to investigate the effect of the silica coating on the oxidation behavior of Ni by TGA, SEM and XRD. Results of the oxidation tests showed that the oxidation rate of Ni was reduced greatly due to the applied thin film. The possible mechanism of the effect of thin film on the oxidation of Ni was discussed.

Effect of Rare Earth on High Temperature Properties of Heat-Resisting Steel

2012 ◽  
Vol 557-559 ◽  
pp. 108-111
Author(s):  
Xiao Liu ◽  
Hu Fei Zhang
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Rare Earth ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Cleavage Fracture ◽  
Oxidation Rate ◽  
High Temperature Mechanical Properties ◽  
Dimple Fracture ◽  
Reduction Of Area

The oxidation resistance and high temperature mechanical properties of FeCrNi heat-resisting steel are analyzed and studied. The results show that the oxidation resistance of the heat-resisting steel is improved remarkably after adding RE. The value of oxidation rate of Sample 1 (without adding RE) is 1.71 times higher than Sample 2, respectively at 1423K. And the value of oxidation rate of Sample 1 is 1.4 times higher than Sample 2, respectively at 1473K. The fracture mode of heat-resisting stainless steel is typical cleavage fracture, but dimple fracture after adding RE into the steel. The high temperature mechanical properties of heat-resisting steel is improved obviously by RE. In comparison with heat-resisting stainless steel without RE, the reduction of area of heat-resisting stainless steel with RE is increased 26.27% at 1123K.

Formation of SiC whiskers from silicon nitride

1992 ◽  
Vol 27 (10) ◽  
pp. 2726-2730 ◽  
Author(s):  
R. V. Krishna Rao ◽  
M. M. Godkhindi
Keyword(s):  
Silicon Nitride ◽  
Sic Whiskers

Effect of Hf Content on Oxidation Resistance of Single Crystal Superalloy at 1000°C

2014 ◽  
Vol 915-916 ◽  
pp. 562-566 ◽  
Author(s):  
Z.X. Shi ◽  
Shi Zhong Liu ◽  
M. Han ◽  
J.R. Li
Keyword(s):  
Grain Size ◽  
Single Crystal ◽  
Oxide Scale ◽  
Oxide Layer ◽  
Oxidation Resistance ◽  
Isothermal Oxidation ◽  
Single Crystal Superalloy ◽  
Ambient Atmosphere ◽  
Directionally Solidified ◽  
Better Than

The specimens of single crystal superalloy DD6 with 0.10% Hf and 0.47% Hf were prepared in the directionally solidified furnace. The effect of Hf content on the isothermal oxidation resistance of the second generation single crystal superalloy DD6 was studied at 1000°Cin ambient atmosphere. Morphology of oxides was examined by SEM, and their composition was analyzed by XRD and EDS. The experimental results show that the oxidation resistance of DD6 alloy with 0.47% Hf is better than that of the alloy with 0.10% Hf. The alloy with different Hf content all obeys parabolic rate law during oxidation for 100h at 1000°C. The increase of Hf content can promote the Al2O3 formation and decreases the proportion of NiO. The oxide grain size and the thickness of the oxide layer all reduce with increasing of Hf content. The oxide scale of the alloy with different Hf content is made up of an outer NiO layer with a small amount of Co3O4, inner Al2O3 and Cr2O3 layer with a small amount of TaO2.

Preparation and ESR Properties of Silicon Nitride Nanowires

2012 ◽  
Vol 164 ◽  
pp. 69-72
Author(s):  
Jin Chen ◽  
Xiao Gang Wang ◽  
Hai Yan Zhang
Keyword(s):  
Carbon Nanotubes ◽  
Phase Composition ◽  
Silicon Nitride ◽  
Oxidation Resistance ◽  
Raw Materials ◽  
Blue Shift ◽  
Ftir Spectra ◽  
Structure Phase ◽  
Ammonia Atmosphere ◽  
Main Component

We prepared Solid silicon nitride nanowires using carbon nanotubes as precursors., Si and SiO2 were used as raw materials,the reaction was carried out in ammonia atmosphere The structure, phase composition, ESR properties and oxidation resistance of the sample were investigated. The results showed that the sizes of the nanorods are 60–80 nm in diameter and up to several microns in length. In the products α-Si3N4 is the main component; the FTIR spectra of the silicon nitride nanowires have blue shift phenomena;The ESR properties show that the as made materials contains a large number of unpaired electrons

Effects of Yttrium on Cyclic Oxidation Resistance of Co-10Cr-5Al Alloy at 700 °C

2014 ◽  
Vol 528 ◽  
pp. 25-29
Author(s):  
Ling Yun Bai ◽  
Xian Chao Xu ◽  
Jun Huai Xiang ◽  
Yun Xiang Zheng ◽  
Jun Wang
Keyword(s):  
Oxide Scale ◽  
Oxidation Resistance ◽  
Oxidation Rate ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Adhesive Property ◽  
Complex Mode ◽  
Rate Law ◽  
Parabolic Rate

The cyclic oxidation behavior of Co-10Cr-5Al alloys in atmosphere at 700 °C was investigated. The addition of 0.3 at.% Y changed the oxidation behavior from the approximate parabolic rate law to complex mode. The scale grown on the surface of Co-10Cr-5Al cracked seriously, while the oxide scale the Y doped alloy had better adhesive property. Yttrium doped in the sample promoted the forming of continuous Al2O3layer and decreased the oxidation rate of Co-10Cr-5Al alloys.

scholarly journals Oxidation Behavior of Multilayer Hard Coatings (TiCN/Al2O3/TiN) in Process of Recycling Coated Multicomponent Hardmetal Scrap

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1796 ◽  
Author(s):  
Hai Kuang ◽  
Dunqiang Tan ◽  
Wen He ◽  
Zhiqiang Yi ◽  
Zhihang Zou ◽  
...  
Keyword(s):  
Oxidation Rate ◽  
Oxidation Behavior ◽  
Isothermal Oxidation ◽  
Hard Coatings ◽  
Hard Alloys ◽  
Al2o3 Layer ◽  
Good Oxidation Resistance ◽  
Element Diffusion ◽  
Negative Effect ◽  
Al2o3 Phase

The coating is one of the biggest problems in the recycling of coated multicomponent hardmetal scraps. The isothermal oxidation behavior of WC-Co multicomponent cemented carbide inserts with a TiCN/Al2O3/TiN hard coating in the recycling process was investigated. The oxidation rate slowed down as the protective coating blocked element diffusion. A rapid oxidation rate was obtained when they were milled into powders and isothermally oxidized at 900 °C. A rapid path for element diffusion was provided by the defects, which were promoted by stress, expansion, and gas volatilization. Both the TiN and TiCN layers were oxidized to a porous TiO2 scale, while the Al2O3 phase remained and the dense Al2O3 layer acted as a barrier for its good oxidation resistance. Pieces of the Al2O3 layer were obviously seen in the final oxides. This provides critical information to reduce the negative effect of coatings and improve the performance of recycled WC powders and hard alloys.

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