摘要:

AbstractDiffusionsschichten werden in großem Umfang industriell genutzt, um die Oberflächeneigenschaften von Maschinenelementen den Anforderungen anzupassen. Diese Schichten werden in der Regel zur Verbesserung des Verschleißverhaltens eingesetzt. Häufig ist es wünschenswert, wenn zugleich eine Verbesserung des Korrosionsverhaltens bewirkt wird.In dieser Arbeit wurde das Korrosionsverhalten verschiedener Diffusionsschichten untersucht. Dazu wurden drei Diffusionsverfahren ausgewählt, nämlich Salzbad‐, Gas‐, und Plasmanitrocarburieren, die an fünf verschiedenen Stählen zur Anwendung gelangten. Die Stähle waren St 52‐3, Ck 45,42 CrMo 4, 30 CrNiMo 8 und × 20 Cr 13. Die Schichtdicken und deren Porositäten warden mit Hilfe der Lichtmikroskopie untersucht. Der Schichtaufbau wurde mittels der Röntgenfeinstrukturanalyse, die Oberflächen‐Kenngrößen mittels des Tastschnittverfahrens bestimmt. Der Korrosionstest wurde mittels Salzsprühnebelprüfung durchgeführt. Die vorherrschenden, durch Korrosion verursachten Schädigungen wurden mittels Rasterelektronenmikroskopie dokumentiert.Es stellte sich heraus, daß grundsätzlich alle Schicht/Substrat‐Kombinationen eine Verbesserung der Korrosionsbeständigkeit gegenüber den Grundwerkstoffen bewirkten. Größere Verbindungsschichten und gleichmäßig ausgebildete Nachoxidationen reduzierten die Korrosionsangriffe am besten. Als beständigste Schicht/Substrat‐Kombinationen gegen Korrosion stellten sich salzbadnitrocarburierte Vergütungsstähle heraus, während die dünnen Verbindungsschichten der plasmanitrocarburie

ISSN:0947-5117    

DOI:10.1002/maco.19970480602

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractStainless steel ground anchors are still rarely used in Europe. A project was initiated to demonstrate the technical and economic performance of stainless steels for such applications.Three different steel grades were examined, i.e. two austenitic grades 1.4311 (‘304LN’) and 1.4406 (‘316LN’) and one duplex grade 1.4362 (‘2304N’). All of them had low carbon contents (<0.03%) and were alloyed with nitrogen to improve their strength properties.Different electrochemical tests were carried out to assess the performance of stainless steel in chloride/sulphate environments. The results confirmed that the investigated stainless steels may be employed for a wide range of corrosive ground anchor e

ISSN:0947-5117    

DOI:10.1002/maco.19970480603

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe corrosion behavior of Fe‐Cr and Fe‐Ni‐Base commercial alloys has been investigated in an argon‐42.6% oxygen‐14.7% bromine gas mixture at 700 °C which was one of the environments encountered in the UT‐3 thermochemical water decomposition reaction process to produce hydrogen. The test alloys were type 304 and 310 stainless steels, Incoloy 800, and Incoloy 825.Two‐dimensional thermodynamic phase stability diagrams were constructed for iron, chromium, nickel, and titanium to predict the condensed corrosion products that are stable with respect to the representative alloying elements when the alloy is exposed to the argon‐42.6% oxygen‐14.7% bromine gas mixture at 700 °C. The oxides were thermodynamically stable phases with respect to the corresponding metals.Post‐reaction treatment of test alloys included discontinuous mass‐change measurements, scanning electron microscopy (SEM), electron probe micro‐analysis (EPMA) for morphological and compositional investigation of the corrosion products, and the X‐ray diffraction (XRD) for phase identification. XRD identified oxides and spinels as corrosion products but low‐melting metal bromides were detected for all alloys with deleterious effects on high‐temperature properties of these alloys during exposure to the environment.The poor corrosion resistance of the test alloys was mainly caused by the cracking and spalling of iron and chromium‐rich oxides and further growth of various metal bromides beneath the oxide scale following prolonged exposure. The high iron content of the test alloys had deleterious effects on the performance o

ISSN:0947-5117    

DOI:10.1002/maco.19970480604

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractSome problems have occured in heat pumps using groundwater, and we have found in the pumped water some bacteria able to induce corrosion (sulphate reducing bacteria, iron oxydizing bacteria…). Before we present any study on the behaviour of metallic materials, we have realized a statistical study on bacteriological contamination of groundwater. We have observed that 45% of the installation were contaminated. But no clear relation can be found between geographical location and the presence of these bacteria.Observation of well by immersed video camera showed a varied resistance to biofilm growth on different materials for casing as steels, PVC, wood, concrete… In some cases we observed an important growth on stainless steels as AISI 304L or 430 grades.Finally, we propose some technical possible solutions for new installations and some prevention to do on actual si

ISSN:0947-5117    

DOI:10.1002/maco.19970480605

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe first assumption was that titanium and its alloy should have excellent corrosion resistance in alkaline hydrogen peroxide bleaching. However, the pulp mill experience of the corrosion resistance of titanium alloy conflict partly with the earlier knowledge. The corrosion of both titanium and titanium alloy was studied in alkaline hydrogen peroxide environment. The cell was equipped with a water circulation loop and chemistry monitoring system. The monitoring system adjusted the pH‐value, hydrogen peroxide concentration and temperature of the solution.Both titanium and titanium alloy dissolved by uniform corrosion in passive state due to the hydrogen peroxide ion. This ion can destroy protective dioxide layer of titanium. The critical concentration of hydrogen peroxide ion could be estimated experimentally and for both titanium and titanium alloy it was 0.008 ± 0.008 M at 80 °C in alkaline hydrogen peroxide ion environment.However, theoretically based on thermodynamic no critical hydrogen peroxide concentration could be found whereas traces of this ion can attack titanium and titanium alloys. The experimentally determined corrosion rate of both titanium and titanium alloy seems to follow an exponential law as a function of hydrogen peroxide ion concentration, which could be explained by the Arrhenius equat

ISSN:0947-5117    

DOI:10.1002/maco.19970480606

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractEs wird über das Korrosionsverhalten von handelsüblichen verzinkten Stahlrohren berichtet, die in einer Warmwasserzirkulation mit einem kathodischen Schutzverfahren eingebaut waren und über den Zeitraum von einem Jahr untersucht wurden. Die Ergebnisse werden denen verzinkter Stahlrohre gegenübergestellt, die in einer vergleichbaren Warmwasseranlage ohne Schutzverfahren installiert wa

ISSN:0947-5117    

DOI:10.1002/maco.19970480607

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480608

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480611

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480613

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480617

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY