T.E.M. Statistical Characterization of Grain Boundaries in Polycrystalline NiO Scales Obtained by High Temperature Oxidation of Nickel

Laves phase (Cr2X) strengthened Cr solid solution [Cr(X)]-based alloys are under development for a variety of high-temperature structural applications. Among the most promising alloys are castings based on the Cr(Ta)-Cr2Ta eutectic, which exhibit room-temperature fracture toughness in the 10-12 MPa√m range and creep rupture lives in excess of 1000 h at 1000° (138 MPa) in air. These alloys exhibit superior high-temperature oxidation resistance to previously developed Cr(Nb)-Cr2 Nb based alloys despite the general similarities of Ta and Nb. In order to optimize high-temperature oxidation resistance an understanding of why the Cr(Ta)-Cr2Ta alloys are more oxidation resistant is needed. Detailed EPMA characterization of the oxidized scaleswas initiated as a first steptowards gaining this understanding.Fig. 1 shows a backscattered electron image of cast and heat treated and heat treated Cr-10Nb at.% after a 6 cycle, 120 h exposure at 1100°C in humid air. Most of the coupon was converted to a complex mixture of Cr-, Nb-, and Cr+ Nb- oxides.

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Characterization of oxide scales to evaluate high temperature oxidation behavior of Ni–20Cr coated superalloys

Materials Science and Engineering A ◽

10.1016/j.msea.2007.01.088 ◽

2007 ◽

Vol 464 (1-2) ◽

pp. 110-116 ◽

Cited By ~ 34

Author(s):

H. Singh ◽

D. Puri ◽

S. Prakash ◽

Rabindranath Maiti

Keyword(s):

High Temperature ◽

High Temperature Oxidation ◽

Oxidation Behavior ◽

Oxide Scales ◽

Temperature Oxidation ◽

High Temperature Oxidation Behavior

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Influence Mechanism of Cu on High Temperature Oxidation Behavior of Titanium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.944.110 ◽

2019 ◽

Vol 944 ◽

pp. 110-119 ◽

Cited By ~ 1

Author(s):

Hang Chen ◽

Guang Bao Mi ◽

Pei Jie Li ◽

Chun Xiao Cao

Keyword(s):

High Temperature ◽

Grain Boundaries ◽

Oxide Layer ◽

High Temperature Oxidation ◽

Oxidation Behavior ◽

Temperature Oxidation ◽

Oxidation Rates ◽

Cu Alloy ◽

Cu Alloys ◽

Oxidation Surface

The oxidation behavior and mechanism of Ti-Cu alloys (0≤w(Cu)≤20%) in the temperature range of 1000°C～1300°C are studied by thermogravimetric analysis(TGA) combined with SEM, EDS and XRD analysis methods. The results show that the oxidation rates of Ti-Cu alloys increase sharply when the temperature rises above 1000°C. The oxidation products have a three-layer structure, from the outside to the inside, which are dense outer oxide layer of TiO2, porous inner oxide layer of low valence oxide of Ti and Cu-enriched layer. With the increase of the temperature, the thicknesses of oxide layers of Ti-Cu alloy increase and the Cu-enriched phase increases gradually and melts. The melting Cu-enriched phase flows to the oxidation surface along the grain boundaries of the oxide layer. The high temperature oxidation resistance of Ti-Cu alloys declines with the increase of Cu content. The main reason is that more liquid Cu-enriched phase is formed and flows to the oxidation surface along the oxide grain boundaries in the Ti-Cu alloy, and Ti and O ions can diffuse more easily along the liquid Cu-enriched phase, which increases the oxidation rates.

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