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High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes)

An International Journal

ISSN for PRINT: 1093-3611

Institutional price:	$604.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2003, Volume7

158 pages

DOI: 10.1615/HighTempMatProc.v7.i2

Issue price - $144.00

INFLUENCE OF DC PLASMA PREHEATING ON OXIDE LAYERS FORMED BY FURNACE HEATING ON LOW CARBON STEEL SUBSTRATES AND RESULTING ADHESION/COHESION OF ALUMINA COATINGS

S. Valette
SPCTS - Science des precedes Ceramique et de Traitements de Surface - UMR CNRS 6638 - University of Limoges -123 Avenue Albert Thomas - 87060 Limoges Cedex - France

A. Denoirjean
Science des Precedes Ceramique et de Traitement de Surface, University of Limoges, UMR CNRS 6638; France

Pierre Lefort
Laboratoire Science des Precedes Ceramiques et Traitements de Surface UMR CNRS 6638 123 Avenue Albert-Thomas F-87060 Limoges Cedex, France

Pierre Fauchais
Laboratoire Sciences des Precedes Ceramiques et de Traitements de Surface, UMR 6638 CNRS-Universite de Limoges, faculte des Sciences et Technique, conventionne avec le CEA n° M08, France

ABSTRACT

In plasma spraying the preheating of low carbon steel substrates (X40) with a rough surface resulting from grit blasting, has received an increased interest because it promotes the adhesion and cohesion (A/C) of alumina coatings. Earlier works have reported the generation of a duplex Fе₃O₄/Fе₂O₃ layer after preheating by the d.c. plasma jet. Improved A/C values were obtained for an increase in Fе₃O₄ content in the oxide layer. Much improved adherence values were achieved with alumina spayed on Fe_1-xO layers. In this case, the Adhesion/cohesion values obtained on smooth substrate (Ra ~ 0.1 mm) were good (~ 40 MPa) and close to those obtained on rough ones (Ra ~ 5 mm). First the time evolution of the Fe_1-xO layer thickness and morphology produced in a controlled atmosphere furnace was studied. Then the influence of the plasma preheating of the wilstite layers was studied by SEM, and XRD analyses. XRD analysis results indicated a slight variation in the oxide phases depending on the preheating cycles. Fе₃O₄ was found to increase when a decomposition of Fe_1-xO into Fе₃O₄ was observed.