Engineering Commons^™

High Temperature Oxidation Study Of Tantalum Carbide-Hafnium Carbide Solid Solutions Synthesized By Spark Plasma Sintering, Cheng Zhang

FIU Electronic Theses and Dissertations

Tantalum carbide (TaC) and hafnium carbide (HfC) possess extremely high melting points, around 3900 ^oC, which are the highest among the known materials. TaC and HfC exhibit superior oxidation resistance under oxygen deficient and rich environments, respectively. A versatile material can be expected by forming solid solutions of TaC and HfC. However, the synthesis of fully dense solid solution carbide is a challenge due to their intrinsic covalent bonding which makes sintering challenging.

The aim of the present work is to synthesize full dense TaC-HfC solid solutions by spark plasma sintering with five compositions: pure HfC, HfC-20 vol.% TaC …

Γ/Γ' Co-Base Superalloys – New High Temperature Materials Beyond Ni-Base Superalloys?, Steffen Neumeier, Christopher H. Zenk, Lisa P. Freund, Mathias Göken

Beyond Nickel-Based Superalloys II

In 2006 a new L1₂ phase, Co₃(Al,W), was discovered in the Co-Al-W system which has led to the development of novel Co-base superalloys with g/g¢ microstructures similar to those of the well-established Ni-base superalloys. First investigations on simple ternary alloys could show that these Co-Al-W based alloys exhibit higher solidus temperatures and show less segregations after casting compared to typical Ni-base superalloys. This leads to the question whether this g/g¢ Co-base superalloys can be regarded as new class of high temperature materials that can compete with or even supersede established Ni-base superalloys.

In the first part of …

Correlation Between Zn-Rich Phase And Corrosion/Oxidation Behavior Of Sn-8zn-3bi Alloy, Xin Zhang, Chong Li, Zhiming Gao, Yongchang Liu, Zongqing Ma, Liming Yu, Hui Jun Li

Faculty of Engineering and Information Sciences - Papers: Part A

The microstructure of Sn-8Zn-3Bi alloy was refined by increasing the solidification rate and the correlation between Zn-rich phase and the corrosion/oxidation behavior of the alloy was investigated. The Zn-rich phase transforms from coarse flakes to fine needles dispersed in the β-Sn matrix with the increase of the cooling rate. The transformation of Zn-rich precipitates enhances the anticorrosive ability of Sn-8Zn-3Bi alloy in 3.5 wt.% NaCl solution. On the contrary, Sn-8Zn-3Bi alloy with a fine needle-like Zn-rich phase shows poor oxidation resistance under air atmosphere, due to the fast diffusion of Zn atoms in Sn matrix.

High Temperature Oxidation Of Indefinite Chill Roll Material Under Dry And Humid Atmospheres, Liang Hao, Zhengyi Jiang, Zhixin Chen, Dongbin Wei, Xiawei Cheng, Jingwei Zhao, Ming Luo, Li Ma, Suzhen Luo, Laizhu Jiang

Faculty of Engineering and Information Sciences - Papers: Part B

In this paper, the isothermal oxidation of the indefinite chill (IC) roll is investigated by using a thermogravimetric analyzer (TGA) from 550 to 700 °C under dry and humid atmospheres. It is found that the oxidation kinetics follow a linear trend and the oxide scale consists of two layers after the oxidation in dry air but three layers in humid air above 600 °C. In dry air, the graphite is covered by the oxide scale above 650 °C. The water vapor accelerates the oxidation of the matrix and the graphite. The graphite is covered by the extension of the oxide …

Breakaway Oxidation Behaviour Of Ferritic Stainless Steels At 1150 °C In Humid Air, Xiawei Cheng, Zhengyi Jiang, Brian J. Monaghan, Dongbin Wei, Raymond Longbottom, Jingwei Zhao, Jianguo Peng, Ming Luo, Li Ma, Suzhen Luo, Laizhu Jiang

Faculty of Engineering and Information Sciences - Papers: Part A

The breakaway oxidation behaviour of ferritic stainless steels 430, 443 and 445 has been investigatedat 1150◦C in humid air. The oxidation kinetics exhibited significant differences among the three ferriticstainless steels. A uniform and steady growing oxide scale was developed on the 430 steel with an evensteel/oxide interface. Local breakdown of the initially protective oxide scale occurred and oxide noduleswere developed on the 443 and 445 stainless steels, resulting in irregular and rough steel/oxide inter-faces. The breakaway oxidation behaviour was significantly influenced by the microstructure and thecomposition of the oxide scale. The Mn-Cr spinel oxide formed on top of the Cr2O3scale …