摘要:

AbstractReview of the papers presented to the Conference and of discussions. The topics dealt with included the various ways in which growing oxide scales can deform to accommodate their growth stresses. According to that plastic deformation occurs by the following mechanisms: dislocation glide, dislocation climb, Herring‐Nabarro stress‐assisted diffusion creep, grain‐boundary sliding, mechanical twinning and viscous flow of amorphous oxides. The deformation depends on the scale configuration and the stress system; many oxide systems are rather plastic at high temperatures, but pores, defect doping elements and second phase inclusions play important parts, too. It is generally accepted that the evidence for some plastic deformation in growing oxide scales is very strong, the most favoured mechanism at high temperatures being diffusion controlled creep associated with grain boundary sliding. Factors influencing adhesion of scales include electrostatic forces at the metalloxide interface, interface irregularities, stress/strain interactions between oxide and metal, stress relaxation in metal and oxide, and the presence of stress raisers such as voids, second phase particles and pores at the metal/oxide interface. The necessity of developing new measuring methods is pointed out

ISSN:0947-5117    

DOI:10.1002/maco.19720230902

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe experimental evidence for stress generation in growing oxide scales is briefly summarised, and the origin of these stresses is discussed. The limited experimental data related to oxide adhesion is discussed, and it is concluded that the adhesion between metal and oxide probably involves chemical interaction, and that the effects of impurities collecting at the interface are not easy to predict. It is emphasised however that the problem of adhesion at the metall oxide interface is complicated by the dynamic nature of the situation, so that it is necessary to postulate a growth mechanism which will allow contact between the oxide and the metal to be maintained. Finally, the problem of plastic flow in the oxide is considered, and it is suggested that some of the evidence which has been adduced to support the idea of large plastic flow is less than entirely convincing. Some of the phenomena may possibly be interpreted in terms of “stress‐directed grow

ISSN:0947-5117    

DOI:10.1002/maco.19720230903

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe microstructural features of scales as formed during the high temperature corrosion of metals can vary considerably. Apart from the obvious differences between scales derived from different metals, even with a given metal the microstructure of the scale is affected by factors such as metal purity and the conditions of exposure, namely the duration and temperature of oxidation and the partial pressure of the oxidant in the atmosphere. In particular variations in grain size and morphology, and in the degree and morphology, and in the degree and nature of porosity can occur; in addition in some systems precipitation of a second phase of variable morphology can take place. Some of these differing structural features in scales are discussed and illustrated.It is suggested that such variations in microstructure will considerably affect the mechanical properties of the scales in which they occur. In general few data concerning mechanical properties, in particular plastic deformation characteristics of scales have been published; furthermore little attempt has been made to assess the possible role of such variations in structure. Rather more information is, however, available from the field of ceramics, and this knowledge is critically reviewed. The usefulness and limitations of such information in relation to the interpretation of the creep behaviour of cobalt monoxide scales is illustrated.

ISSN:0947-5117    

DOI:10.1002/maco.19720230904

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe advantages and limitations of microhardness measurements in assessing the mechanical behaviour of oxidizing specimens are outlined. Hardness values for a wide range of oxides at ambient temperatures are presented and discussed in terms of the oxide structures. Hardness profiles across doped scales, produced by the oxidation of alloys, are correlated with concentration profiles obtained by electron probe microanalysis. The implications of oxide hardness in understanding the behaviour of materials at ambient and elevated temperatures are considered.

ISSN:0947-5117    

DOI:10.1002/maco.19720230905

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe mechanical properties of surface scales on iron and nickel have been previously measured, during growth at high temperatures, using a vibrational technique (1,2). The feasibility of using this technique to study other systems is discussed and, in particular, its application to high‐temperature, oxidation rate and oxide stability on the results are considered and values of the Youngs modulus of the oxide scale on Nimonic 90 over a range of temperatures have been determine

ISSN:0947-5117    

DOI:10.1002/maco.19720230906

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe dissolution of sulphur in copper oxides leads to modifications of the ionic and electronic defect structures, causing anion and cation mobilities and possibly the electron hole concentration to be increased. No clear explanation or mechanism for these effects is available so far. The increased creep rate in the presence of sulphur dioxide as well as the variations of the electrical conductivity and the thermoelectric effect require further study for a reasonable interpretation. The formation of SO3may play some role when oxygen and sulfur dioxide are present simultaneously.

ISSN:0947-5117    

DOI:10.1002/maco.19720230907

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractDes variations de température effectuées au cours de l'oxydation d'un métal ont un effet différent sur la cinétique d'oxydation, selon le métal considéré. Cette influence est discutée dans le cas du zirconium et comparée à celle observée dans le cas du cobalt, ces deux métaux se comportant d'une maniè're différente. En effet, une diminution brutale de la température au cours de l'oxydation du zirconium entraîne une accélération marquée de l'oxydation. Par contre, dans le cas du cobalt, une telle variation de température a une influence négligeable sur la vitesse ultérieure de l'oxydation. Ces résultats sont discutés en termes de plasticité relati

ISSN:0947-5117    

DOI:10.1002/maco.19720230908

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractPhosphathaltige Additive können als Inhibitoren gegen die Korrosion durch Vanadiumpentoxid wirken, wenn sichergestellt ist, daß in der Schmelze ein ausreichend hoher Phosphatgehalt vorliegt. Zu geringe Phosphatgehalte führen — da dann die Leitfähigkeit der Schmelze erhöht ist — zu einer Verstärkung der Korrosion. Der Gehalt der Schmelze an VIVeignet sich nicht als Maß für die Aggressivität, denn bei hohen Phosphatgehalten ist die Aggressivität besonders bei hohen VIV:VV‐Verhältn

ISSN:0947-5117    

DOI:10.1002/maco.19720230909

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19720230910

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19720230911

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY