Abstract
The structure of thermally sprayed coatings consists of lamellae which are oriented parallel to the substrate surface. Coatings most often consist of a metallic bond coat and a ceramic overlay, although in principle there is no restriction to the number of components in any coating system. The lamellae separate and fracture by distinctive mechanisms which are reflected in the failure morphology, and these may be described as adhesive (between the coating and substrate), cohesive (within the coating), or mixed mode.
There is a large variability in the failure stress for any nominally identical group of coatings. This variability in coating strength is initially assumed to arise from the defective nature of the coating. A lower bound for the fracture toughness of alumina coatings can be calculated as 0.2 MNm-3/2. The coating strength values may also be treated as belonging to the statistical distribution of the Weibull function. The Weibull modulus of the coating strength varied from 1.4 to 3.8. This analysis infers that the flaw size within coatings is highly variable and that the flaws are non-uniformly dispersed. The present work focuses on the question of whether tensile adhesion tests are an appropriate testing method for thermally sprayed materials.
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References
D.A. Gerdeman and N.L. Hecht:Arc Plasma Technology in Materials Science, 206 pp, Springer-Verlag: New York, 1972.
American Welding Society:Thermal Spraying—Practice, Theory and Application, AWS, Inc., 1985.
C.C. Berndt and R. McPherson:A Fracture Mechanics Approach to the Adhesion of Plasma Sprayed Coatings, pp. 310–316, The 9th Int. Thermal Spraying Conf., May 19–23, 1980, The Hague, Netherlands, Nederlands Instituut voor Lasteniek, 1980. Discussion on pp. 40–41 of Rapporteurs Volume.
P.C. Hopman: “The Direct Pull-Off Test,”JOCCA, 1984, vol. 7, pp. 179–184.
J. Sickfeld: “Pull-Off Test, an Internationally Standardized Method for Adhesion Testing—Assessment of the Relevance of Test Results,” pp. 543–567, Adhesion Aspects of Polymeric Coatings. K.L. Mitall (Ed.), Plenum, New York, 1983.
C.C. Berndt and R. McPherson: “The Adhesion of Plasma Sprayed Ceramic Coatings to Metals,”Mater. Sci. Res., 1981, vol. 14, pp. 619–628.
ASTM C633-69: “Standard Method for Adhesion or Cohesive Strength of Flame-Sprayed Coatings,” American Society for Testing and Materials, Philadelphia, 1969.
DIN 50 160: “Determination of Adhesive Strength in the Traction-Adhesive Strength Test,” DIN-Normen, Beuth Verlag Gmbht, Berlin 30, August 1981.
AFNOR NF A91-202-79: “Characteristics and Methods of Test for Metal Spraying,” Association Francaise de Normalisation, Tour Europe, Cedex 792880, Paris, October 1979.
JIS H 8666-80: “Thermal Sprayed Ceramic Coatings,” Japanese Standards Association, 1-24, Akasaka 4, Minato-ku, Tokyo, Japan, 1981.
SAE AMS 24378: “Coating, Plasma Spray Deposition,” SAE, 400 Commonwealth Dr., Warrendale, PA, 1 January 1986.
F.J. Hermanek: “Determining the Adhesive Cohesive Strength of Thin Thermally Sprayed Deposits,”Weld. J., 1978, vol. 57, pp. 31–35.
W.F. Brown, Jr. and J.E. Srawley: “Plain Strain Crack Toughness Testing of High Strength Metallic Materials,” p. 15, ASTM STP410, American Society for Testing and Materials, 1969.
A.S. Telelman and A.J. McEvily, Jr.: “Fracture of Structural Materials,” John Wiley & Sons Inc, New York, 1967.
T.E. Strangman: “Thermal Barrier Coatings for Turbine Airfoils,” Report 21-4892, Garrett Turbine Engine Company, Phoenix, AZ, April 10, 1984.
I. Kvernes and M. Seiersten: “Developments and Problems in the Use of Thermal Barrier Coatings on Metals,” pp. 615–620High Temperature Corrosion. R.A. Rapp (Ed.), NACE, Houston, TX, 1983.
S.B. Batdorf: “Fundamentals of the Statistical Theory of Fracture,”Fracture Mechanics of Ceramics, pp. 1–30, vol. 3. R.C. Bradt, D.P.H. Hasselman, F.F. Lange (Eds.), Plenum Press, New York, 1978.
A.G. Evans: “A General Approach for the Statistical Analysis of Fracture,” Fracture Mechanics of Ceramics, pp. 31–49, vol. 3. R.C. Bradt, D.P.H. Hasselman, F.F. Lange (Eds.), Plenum Press, New York, 1978.
B. Bergman: “On the Estimation of the Weibull Modulus,”J. Mater. Sci. Letters, 1984, vol. 3, pp. 689–692.
S.J. Grisaffe: “Analysis of Shear Bond Strength of Plasma-Sprayed Alumina Coatings on Stainless Steel,” NASA TN D-3113, July 16, 1965.
BS 5350: Part C3: “Adhesives: Determination of Bond Strength in Direct Tension,” British Standards Institution, Maylands Av., Hemel Hempstead, Horts, UK, 1978.
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Berndt, C.C. Tensile adhesion testing methodology for thermally sprayed coatings. J. Materials Engineering 12, 151–158 (1990). https://doi.org/10.1007/BF02834068
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DOI: https://doi.org/10.1007/BF02834068