Intermediate-temperature oxidation behavior of Ti2AlC in air

2002 ◽  
Vol 17 (11) ◽  
pp. 2974-2981 ◽  
Author(s):  
X. H. Wang ◽  
Y. C. Zhou
Keyword(s):  
Raman Spectroscopy ◽  
Rate Constant ◽  
Oxidation Behavior ◽  
Parabolic Rate Constant ◽  
Oxidation Products ◽  
Scale Morphology ◽  
Temperature Oxidation ◽  
Good Oxidation Resistance ◽  
Parabolic Rate ◽  
Anomalous Oxidation

The isothermal oxidation behavior of Ti2AlC at intermediate temperatures of 500, 600, 700, 800, and 900 °C in flowing air was investigated by means of thermogravimetric analysis, x-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM)/energy dispersive spectroscopy. An anomalous oxidation with higher kinetics at lower temperatures of 500 and 600 °C was observed although Ti2AlC exhibited good oxidation resistance at higher temperatures. As revealed by SEM scale morphology observation, oxidation-induced cracks present at temperatures of 500 and 600 °C resulted in poor protectivity of scales and accounted for the anomalous oxidation. The weight gain data for the remaining temperatures were analyzed with an instantaneous parabolic rate constant method by assuming a parabolic rate law. The variations of instantaneous parabolic rate constant with time reflected the complexity of the oxidation behavior of Ti2AlC at intermediate temperatures. These variations were discussed from the viewpoint of phase transformation of oxidation products on the basis of XRD, Raman spectroscopy, and SEM scale morphology observation. As indicated by XRD and Raman spectra, the scale formed on Ti2AlC at higher temperature was stable α–Al2O3 and rutile TiO2, while transition aluminas of γ–Al2O3, δ–Al2O3, θ–Al2O3, and TiO2 (anatase) were detected at lower temperatures. The whisker morphology of θ–Al2O3 at 800 °C and ridged morphology of α–Al2O3 at 800 and 900 °C were confirmed by SEM.

Effects of Yttrium on Cyclic Oxidation Resistance of Co-10Cr-5Si Alloy

2013 ◽  
Vol 785-786 ◽  
pp. 914-917
Author(s):  
Jun Huai Xiang ◽  
Xian Chao Xu ◽  
Ling Yun Bai ◽  
Yun Xiang Zheng ◽  
Huai Shu Zhang
Keyword(s):  
Oxidation Resistance ◽  
Rate Constant ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Parabolic Rate Constant ◽  
Cooling Process ◽  
Parabolic Rate

The cyclic oxidation behavior of Co-10Cr-5Si alloys with and without Y in atmosphere at 800 °C was investigated. The addition of 0.3 at.% Y decreased the average parabolic rate constant from 4.45×10-10g2cm-2s-1to 3.58×10-10g2cm-2s-1. The thin scales grown on Co-10Cr-5Si alloys were mainly composed of an outer CoO layer, followed by an inner protective SiO2layer. However, the scales can not be observed for Co-10Cr-5Si-0.3Y alloy, probably due to the spallation of the scales during the cooling process. The addition of 0.3 at.% Y improved the cyclic oxidation resistance of the Co-10Cr-5Al alloy.

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

2014 ◽  
Vol 525 ◽  
pp. 154-157
Author(s):  
Jun Huai Xiang ◽  
Xian Chao Xu ◽  
Ling Yun Bai ◽  
Yun Xiang Zheng ◽  
Huai Shu Zhang
Keyword(s):  
Oxidation Resistance ◽  
Rate Constant ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Parabolic Rate Constant ◽  
Parabolic Rate

The cyclic oxidation behavior of Co-10Cr-5Si alloys with and without Y in atmosphere at 700 °C was investigated. The addition of 0.3 at.% Y decreased the average parabolic rate constant from 4.39×10-10g2cm-2s-1to 3.42×10-10g2cm-2s-1. The surface components with and without Y were both composed of an outer CoO and inner protective SiO2. There were more SiO2formed when Y doped into the alloy. The addition of 0.3 at.% Y improved the cyclic oxidation resistance of the Co-10Cr-5Al alloy.

Isothermal and Cyclic Oxidation Behavior of Turbine Blade Alloys

2006 ◽  
Author(s):  
N. S. Cheruvu ◽  
K. T. Chiang
Keyword(s):  
Turbine Blade ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Parabolic Rate Constant ◽  
Isothermal Oxidation ◽  
Isothermal Exposure ◽  
Temperature Oxidation ◽  
Rate Laws ◽  
Parabolic Rate ◽  
Kinetics Of

Oxidation behavior of two nickel-based turbine blade alloys has been investigated at three temperatures ranging from 950°C to 1066°C. Thermogravimetric analysis (TGA), isothermal exposure and cyclic oxidation tests were conducted on GTD-111 (Ni-14.1Cr-3.7W-9.2Co-1.5Mo-3.1A1-4.9Ti-0.02Cb-2.93Ta-0.11C) and IN-738 (Ni-16.0Cr-2.6W-8.1Co-1.6Mo-3.5A1-3.4Ti-0.7Cb-1.6Ta-0.10C) blade alloys. TGA results showed that the oxidation kinetics of both alloys obey parabolic rate laws. The GTD-111 material exhibited a higher parabolic rate constant than IN 738 at all temperatures investigated. Cyclic oxidation behavior of these alloys was compared by plotting the weight change results as a function of thermal cycles. Consistent with the TGA results, cyclic oxidation test results also showed that GTD-111 was less resistant to high-temperature oxidation as compared to the IN-738 alloy. To characterize the oxide scales, a series of short term isothermal oxidation tests were conducted and the spalled scale after oxidation exposure was collected and analyzed by energy-dispersive x-ray analysis (EDX) as a function of aging time. The composition of the scales varied between the alloys. The variation of oxidation behavior of these alloys is discussed with respect to the composition differences between the two alloys.

scholarly journals Additively Manufactured NiTi and NiTiHf Alloys: Estimating Service Life in High-Temperature Oxidation

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2104 ◽  
Author(s):  
Hediyeh Dabbaghi ◽  
Keyvan Safaei ◽  
Mohammadreza Nematollahi ◽  
Parisa Bayati ◽  
Mohammad Elahinia
Keyword(s):  
High Temperature ◽  
Oxidation Rate ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Early Stage ◽  
Niti Alloy ◽  
Temperature Oxidation ◽  
X Ray ◽  
Rate Law ◽  
Parabolic Rate

In this study, the effect of the addition of Hf on the oxidation behavior of NiTi alloy, which was processed using additive manufacturing and casting, is studied. Thermogravimetric analyses (TGA) were performed at the temperature of 500, 800, and 900 °C to assess the isothermal and dynamic oxidation behavior of the Ni50.4Ti29.6Hf20 at.% alloys for 75 h in dry air. After oxidation, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used to analyze the oxide scale formed on the surface of the samples during the high-temperature oxidation. Two stages of oxidation were observed for the NiTiHf samples, an increasing oxidation rate during the early stage of oxidation followed by a lower oxidation rate after approximately 10 h. The isothermal oxidation curves were well matched with a logarithmic rate law in the initial stage and then by parabolic rate law for the next stage. The formation of multi-layered oxide was observed for NiTiHf, which consists of Ti oxide, Hf oxide, and NiTiO3. For the binary alloys, results show that by increasing the temperature, the oxidation rate increased significantly and fitted with parabolic rate law. Activation energy of 175.25 kJ/mol for additively manufactured (AM) NiTi and 60.634 kJ/mol for AM NiTiHf was obtained.

Oxidation behavior of bulk Ti3SiC2 at intermediate temperatures in dry air

2006 ◽  
Vol 21 (2) ◽  
pp. 402-408 ◽  
Author(s):  
H.B. Zhang ◽  
Y.C. Zhou ◽  
Y.W. Bao ◽  
J.Y. Wang
Keyword(s):  
Phase Transformation ◽  
Low Temperatures ◽  
Driving Force ◽  
Oxidation Behavior ◽  
Isothermal Oxidation ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Dry Air ◽  
High Oxidation ◽  
Anomalous Oxidation

The isothermal oxidation behavior of bulk Ti3SiC2 at intermediate temperatures from 500 to 900 °C in flowing dry air was investigated. An anomalous oxidation with higher kinetics at lower temperatures was observed. This phenomenon resulted from the formation of microcracks in the oxide scales at low temperatures. The generation of these microcracks was caused by a phase change in the oxide products, i.e., the transformation of anatase TiO2 to rutile TiO2. This phase transformation resulted in tensile stress, which provided the driving force for the formation of the microcracks during oxidation. Despite the existence of microcracks, the intermediate-temperature oxidation of Ti3SiC2 generally obeyed the parabolic rate law and did not exhibit catastrophic destruction due to the fact that cracks occurring in the oxide layers were partially filled with amorphous SiO2. Therefore, further high oxidation kinetics was prevented.

Isothermal Oxidation Behavior of AlN-TiB2 Ceramics Synthesized by SHS-HIP

2013 ◽  
Vol 575-576 ◽  
pp. 170-173
Author(s):  
Li Juan Zhou ◽  
Yun Xia Zhao ◽  
Hong Bo Li ◽  
Yong Ting Zheng ◽  
Fan Tao Meng
Keyword(s):  
High Temperature ◽  
Oxidation Behavior ◽  
Hot Isostatic Pressing ◽  
Isothermal Oxidation ◽  
Oxidation Products ◽  
Aluminum Borate ◽  
Temperature Synthesis ◽  
Good Oxidation Resistance ◽  
High Temperature Synthesis ◽  
Conductive Ceramics

sothermal oxidation behavior of the AlN-TiB2 conductive ceramics prepared by self-propagating high-temperature synthesis and hot isostatic pressing (SHS-HIP) was evaluated in a temperature range from 900 to 1400 °C for exposure times from 1 to 16 h in air. The oxidation experimental results show that the conductive ceramics have a good oxidation resistance below 1200 °C. The oxidation products on the sample surfaces are mainly composed of Al2TiO5, TiO2 and aluminum borate phases.

High Temperature Oxidation Behaviour of Detonation-Gun-Sprayed Cr3C2-NiCr-CeO2 Coatings on Inconel-718 at 900°C

2014 ◽  
Author(s):  
Sekar Saladi ◽  
Jyoti V. Menghani ◽  
Satya Prakash
Keyword(s):  
High Temperature ◽  
Inconel 718 ◽  
High Temperature Oxidation ◽  
Parabolic Rate Constant ◽  
Coated Specimen ◽  
Oxidation Products ◽  
Temperature Oxidation ◽  
X Ray ◽  
Heating And Cooling ◽  
Detonation Gun

The high temperature oxidation behavior of detonation-gun sprayed Cr3C2-NiCr coatings with and without 0.4 wt. % CeO2 additive on Ni-based superalloy inconel-718 is comparatively discussed in the present study. Oxidation studies were carried out at 900°C for 100 cycles in air under cyclic heating and cooling conditions on bare and coated superalloys. The thermo-gravimetric technique was used to establish kinetics of oxidation. X-ray diffraction, SEM/EDAX and X-ray mapping techniques were used to analyze the oxidation products of bare and coated samples. The results indicate that Cr3C2-NiCr-CeO2 coated specimen showed better oxidation resistance. The overall weight gain and parabolic rate constant of Cr3C2-NiCr-CeO2 coated specimen was found to be lowest in the present study signifying that the addition of CeO2 in Cr3C2-NiCr powder has contributed to the development of adherent and dense oxide scale on the coating at elevated temperature.

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