Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    The deformation behavior of NiO scales on Ni in argon and air at temperatures from 20 to 800°C with respect to the relief of growth stresses (1994)
    Springer
    Oxidation of metals 42 (1994), S. 109-144 
    Details
    ISSN: 1573-4889
    Keywords: acoustic emission measurements ; compression testing ; nickel oxide ; oxide-scale failure ; pseudoplasticity ; TEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Stresses formed in oxide scales due to oxide growth are usually of a compressive nature, and there is still some debate on how these stresses are accommodated. While the deformation behavior of oxide scales under tensile stresses can be regarded as fairly well understood, there are many open questions concerning scale deformation and cracking under compressive straining. Therefore, the NiO scale formed on two different grades of Ni was chosen as a model system for compression tests with strain rates ranging from 8×10−4 to 8×10−8 s−1 in the temperature range of 20 to 800°C. Test environments were air and argon, and accompanying acoustic-emission measurements were taken in order to detect the beginning of oxide-scale cracking during straining. As a result the critical-strain values at the beginning of mechanical-scale damage could be determined quantitatively and explained consistently by model considerations. Furthermore, SEM and TEM investigations, backed up by sulfur decoration of microcracks at the end of the tests, revealed that at elevated temperatures a major deformation mechanism under these conditions takes the form of dynamic equilibrium of continuous microcracking with superimposed oxide-healing processes, making compressive strains of 10% and more possible without macroscopic scale failure. It is, therefore, assumed that a major mechanism of growth stress relief in oxide scales occurs via microcracking and scalecrack healing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061927
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    XRD Investigations of the Phosphorus Effect on the Oxidation of TiAl Alloys by High-Resolution Methods (2000)
    Springer
    Oxidation of metals 54 (2000), S. 317-337 
    Details
    ISSN: 1573-4889
    Keywords: TiAl ; oxidation ; phosphorus ; microdiffraction ; doping ; rutile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Recently it has been found that very small amounts (a few 100 ppm) of Padded to γ -titanium aluminide can significantly alter the oxidationbehavior between 973 and 1273 K. The mechanism responsible for this changeis, however, still not clear. In the present study, phosphorus wasincorporated into the surface of TiAl (containing 50 at.% Al) by ionimplantation and oxidation tests were carried out at 1173 K inair. Improvement of oxidation resistance is only temporary up to 100 hr forphosphorus-implanted TiAl. After 100 hr, the oxidation rate increases andbreakaway oxidation follows. XRD and EPMA showed that the breakawayoxidation is connected with massive nitride formation. Two different modelsare proposed which can explain the effect of phosphorus additions on theoxidation kinetics of TiAl during the protective stage within the first100 hr. The breakaway effect can be explained by penetration of air to themetal–oxide interface zone because of microcrack formation in theoxide scale, which was experimentally proved by acoustic-emission analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004606513758
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    The healing behavior of protective oxide scales on heat-resistant steels after cracking under tensile strain (1986)
    Springer
    Oxidation of metals 25 (1986), S. 409-421 
    Details
    ISSN: 1573-4889
    Keywords: heat-resistant steels ; oxide-scale crack healing ; protective capabilities ; constantextension-rate tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The healing of cracks in protective oxide scales on four heat-resistant steels has been investigated at 800°C in constant-extension-rate tests, in metallographie and in SEM-examinations. The experimental results suggest the existence of a critical strain rate below which crack healing leads to an instant repair of the cracked scale thuspreventing increased internal corrosion. The existence of this critical strain rate can be explained by model considerations, the results of which are in agreement with the results from the experiments. On the basis of scale cracking data from a previous paper and healing data in the present paper “scale cracking/healing maps” have been developed characterizing the protective capabilities of the oxide scales under tensile strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01072918
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Behavior of oxide scales on 2.25Cr-1Mo steel during thermal cycling. I. Scales formed in oxygen and air (1989)
    Springer
    Oxidation of metals 31 (1989), S. 1-34 
    Details
    ISSN: 1573-4889
    Keywords: cyclic oxidation ; 2.25-1Mo steel ; acoustic-emission technique ; oxide-scale buckling and cracking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The acoustic-emission (AE) technique has been applied to study scale-damage processes during thermal cycling of a tube, preferentially between 600 and 300°C in air, oxygen, and air + 0.5% SO2. The AE measurements were accompanied by optical and electron-optical investigations on tube rings exposed to the same cycling conditions. During the first period of cycling, a scale rich in hematite is formed. It suffers compressive stresses during cooling. The result is a buckled multilayered scale with separated lamellae. The scaling rate is lower than under isothermal conditions. AE signals start after 175°C cooling. After longer exposure times, the scale contains an increasing amount of magnetite and becomes more compact. The scaling rate increases and is comparable to that under isothermal conditions. AE signals are already observed after 50°C cooling and are correlated with crack formation in the magnetite caused by tensile stresses there. The addition of SO2 to air enhances the crack-healing process due to higher Fe diffusion in FeS. The scale is more compact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665485
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Behavior of oxide scales on 2.25Cr-1Mo steel during thermal cycling. II. Scales grown in water vapor (1989)
    Springer
    Oxidation of metals 31 (1989), S. 35-69 
    Details
    ISSN: 1573-4889
    Keywords: cyclic oxidation ; water vapor ; 2.25Cr-1Mo steel ; acoustic emission technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The acoustic emission (AE) technique has been applied to identify scale cracking during thermal cycling of tubes of 2.25Cr-1Mo steel. The scale morphology and failure mode were investigated by light and electron optical methods. The scale formed at 600°C in water vapor consists of an outer magnetite and an inner, chromium-containing spinel layer. Cooling leads to tensile stresses in the scale that cause macro and microcrack formation in the scale. At constant-cycle parameters, a characteristic set of crack length and crack density is established. Changes in the cycle parameters also change the crack length and crack density. The experimental results can be described by a model developed by Hasselmann assuming a large number of noninteracting microcracks in a ceramic plate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665486
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Cyclic-oxidation behavior of TiAl and of TiAl alloys (1993)
    Springer
    Oxidation of metals 39 (1993), S. 93-106 
    Details
    ISSN: 1573-4889
    Keywords: cyclic oxidation ; TiAl ; TiAl alloys ; scale spallation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The cyclic-oxidation behavior of (in w/o) Ti-36Al, Ti-35Al-0.1C, Ti-35Al-1.4V-0.1C and Ti-35Al-5Nb-0.1C was studied between 800 and 1000° C in air. A few experiments were also performed in oxygen. Scale spallation after oxidation in air occurs during cooling on TiAl, TiAl-C, and TiAl-V at or close to the metal/scale interface when a critical scale thickness has been achieved. This process repeats and can lead to a stratified scale. These three materials form scales composed of an inward-growing fine-grain mixture of TiO2-Al2O3 and an outward-growing coarse-grain TiO2 layer or TiO2+Al2O3 mixture. The TiAl-Nb alloy had a significantly different behavior. The scale on this material grew very slowly because a protective Al2O3 layer formed at the metal/scale interface. This behavior resulted in much better resistance to spallation because the critical scale thickness was reached only after a much longer time, and is different from the behavior of the other three alloys. Oxidation in air leads to slight nitridation of the subsurface zone beneath the scale. In comparison to oxidation in air, oxidation in oxygen improves the cyclicoxidation behavior. Whereas the scale formed in air was uniformly thick over the entire surface, the scale grown in oxygen varied locally in structure and thickness. A large fraction of the surface was covered with a thin Al2O3 layer, while the remaining part formed a two-layer scale similar to that formed in air. The results are discussed briefly in the light of a recently published model for scale spallation under compressive stress, however, quantitative estimations are not possible due to a lack of relevant data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666612
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Behavior of oxide scales on 12Cr-1Mo steel during thermal cycling (1993)
    Springer
    Oxidation of metals 39 (1993), S. 389-410 
    Details
    ISSN: 1573-4889
    Keywords: cyclic oxidation ; 12Cr-1Mo steel ; acoustic emission ; oxide-scale failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Soot-blower operation leads to thermal-cyclic-oxidation conditions of heat-resistant steels in conventional power stations. The consequence may be failure of the protective oxide scales and increased corrosive attack. The behavior of protective oxide scales on 12Cr-1Mo steel was investigated under isothermal conditions at 650°C and under thermal cycling conditions between 650 and 300°C (200°C). The tests were performed in air, air + 0.5%SO2, simulating the fire side, and Ar-5% H2-50% H2O, simulating the steam side. Complete heat-exchanger tubes were used as specimens. The main instrument for the detection of scale failure was acoustic-emission analysis. In air and air + 0.5% SO2 the M2O3 scales with M = Fe, Cr were very thin and did not show significant failure either during isothermal or during cyclic oxidation. The thicker scales formed in Ar-5% H2-50% H2O, consisting of several partial layers, failed even during isothermal oxidation due to geometrically-induced growth stresses in the scale. Thus, in the thermal-cycling cooling periods there was only very little additional scale cracking. The scale behavior can be explained consistently by applying the existing quantitative models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664663
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    The cyclic-oxidation behavior of several nickel-base single-crystal superalloys without and with coatings (1994)
    Springer
    Oxidation of metals 41 (1994), S. 271-300 
    Details
    ISSN: 1573-4889
    Keywords: cyclic oxidation ; single-crystal superalloys ; coating, reactive-element effect ; acoustic emission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several commerical single-crystal superalloys (CMSX-2, CMSX-3, CMSX-4, CMSX-6, SRR 99) and some laboratory versions of one of them (CMSX-4) with various Y additions were investigated concerning their cyclic-oxidation resistance in air at 1000 and 1150°C. The investigations also included two materials (CMSX-6, SRR 99) with an RT-22 coating. Weight changes and acoustic emission were recorded up to 1000 cycles and scales, coatings, and substrates were characterized by metallography, SEM, and microprobe in postexperimental investigations. The best cyclic-oxidation behavior and excellent resistance to spalling even at 1150°C were shown by a laboratory version of CMSX-4 containing between 10 and 60 ppm Y. While at 1000°C interdiffusion can be taken as tolerable for the coated alloys, there is rapid degradation of the coating by interdiffusion at 1150°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01080784
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    TEM investigations of the early stages of TiAl oxidation (1996)
    Springer
    Oxidation of metals 46 (1996), S. 255-285 
    Details
    ISSN: 1573-4889
    Keywords: electron diffraction ; intermetallic ; oxidation ; TEM ; titanium aluminide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The early stages of TiAl oxidation at 900°C and 1000°C in air have been investigated by transmission electron microscopy (TEM). The investigations revealed that at the beginning of oxidation, i.e., after 4 min, TiO2 and Al2O3 grow in a preferential orientation on the γ-TiAl substrate. After 4 h of oxidation an oxide scale structure can already be found similar to that known from long-term oxidation. In addition, besides α-Al2O3, the formation of a second aluminum oxide phase and of titanium nitrides is observed. The processes at the metal-oxide interface of oxidation in the early stages, consisting of a repeated cycle of Al2O3 formation, Al2O3 dissolution, outward migration of Al through the scale, and reprecipitation of Al2O3 in the outer scale, are described by a model. The four stages observed in the kinetics of TiAl oxidation are explained on the basis of the results obtained and the structure of the oxide scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01050799
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Oxidation of the intermetallics MoSi2 and TiSi2—A comparison (1997)
    Springer
    Oxidation of metals 47 (1997), S. 139-203 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; MoSi2 ; TiSi2 ; air ; oxygen ; O and Si transport in SiO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of two MoSi2 variants, one Mo-rich and one Si-rich, and TiSi2 was investigated between 1000 and 1400°C in air, oxygen and an 80/20-Ar/O2 mixture. A protective SiO2 scale develops on MoSi2 in all atmospheres in the temperature range investigated. The SiO2 modification changes around 1300°C from tridymite to cristobalite. This change in SiO2 modification seems to cause an enhanced formation of SiO2 and evaporation of MoO3. The SiO2 grows at the MoSi2-scale interface. In air a two-layer scale grows on TiSi2 between about 1000 and 1200°C with an inner inwards growing fine-grain mixture of SiO2 + TiO2 and an outer outward-growing TiO2 partial layer. TiN formation in the transient oxidation is responsible for the formation of the inner mixed partial layer because in N -free atmospheres a scale of a SiO2 matrix with some Ti oxide precipitates inside is formed. A one-layer scale structure similar as that in N-free atmosphere is found on TiSi2 in air at T 〉 1200°C. In oxygen the TiO2 precipitates grow as needles mostly oriented perpendicular to the surface. Due to the faster oxygen transport in TiO2 compared with SiO2, these TiO2 needles act as “oxygen pipes,” causing an enhanced oxidation of TiSi2 in front of these needles. The SiO2 scale dissolves about 1–2% TiO2. This doping causes a mixed oxygenand Si transport with the consequence that the SiO2 scale on TiSi2 grows partly by oxygen transport inwards and Si transport outwards. The SiO2 modification is cristobalite over the entire temperature range investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01682375
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...