Abstract
The influence of strain history on the oxidation and mechanical degradation of an aluminide coating was examined by induction heating of stepped-disk specimens. The coating was applied to a single-crystal Ni-base superalloy (RENÈ N4) by pack aluminization. The anisotropic elasticity of the single-crystal substrate allowed simultaneously subjecting the aluminide coating to different strain amplitudes. Two distinct modes of coating degradation were observed for tests performed in air between temperature limits of 520 °C and 1080 °C: scalloping (spatially periodic surface oxidation and roughening) and cracking. The degree of scalloping became more severe as the compressive strain imposed on the coating was increased. Six thousand cycles between peak strains of -0.20 and 0.007 pct produced uniform surface oxidation, without scalloping, whereas 6000 cycles between peak strains of -0.56 and 0.01 pct gave oxidation and scalloping to 80 pct of the coating thickness. Cracks along coating grain boundaries were observed after 6000 cycles between peak strains of -0.45 and 0.16 pct. The depth of scalloping was found to correlate approximately with peak compressive substrate strain. Based on this correlation, a mechanism for scallop initiation and growth involving cyclic breakdown of the surface oxide and irreversible cyclic creep of the coating is proposed. Cracking along coating grain boundaries is attributed to tensile strains applied below the transition temperature of the coating. The results obtained from this study indicate that cyclic strain history is an important variable which should be included when determining the oxidation rate of coatings and alloys.
Similar content being viewed by others
References
E.D. Thulin, D.C. Howe, and I.D. Singer: NASA Report No. CR-165608, Pratt & Whitney Aircraft Group, East Hartford, CT, 1982.
J.W. Holmes: Doctoral Thesis, Massachusetts Institute of Technology, Cambridge, MA, Sept. 1986.
M. Kaufman: TMS-AIME, Paper No. F82-11, 1982.
F.S. Pettit and G.W. Goward: inMetallurgical Treatises, J.K. Tien and J.F. Elliott, eds., TMS-AIME, Warrendale, PA, 1981, pp. 603–19.
J.A. Goebel, F.S. Pettit, and G.W. Goward:Metall. Trans., 1973, vol. 4, pp. 261–78.
J.L. Smialek:Metall. Trans., 1971, vol. 2, pp. 913–20.
G.W. Goward, D.H. Boone, and C.S. Giggins:Trans. ASM, 1967, vol. 60, pp. 228–41.
M.J. Fleetwood:J. Inst. Met., 1970, vol. 98, pp. 1–7.
J.L. Smialek and C.E. Lowell:J. Electrochem. Soc., 1974, vol. 121 (6), pp. 800–05.
H.M. Hindam and W.W. Smeltzer:J. Electrochem. Soc., 1980, vol. 127 (7), pp. 1630–35.
G.C. Wood and F.H. Stott:Br. Corros. J., 1971, vol. 6, pp. 247–56.
N.R. Lindblad:Oxid. Met., 1969, vol. 1 (1), pp. 143–50.
P. Steinmetz, B. Roques, B. Dupre, C. Duret, and R. Morbioli:in High Temperature Protective Coatings, S.C. Singhai, ed., TMS-AIME, Warrendale, PA, 1982, pp. 135–57.
J.W. Holmes, F.A. McClintock, K.S. O’Hara, and M.E. Conners: inLow Cycle Fatigue—Directions For The Future, ASTM STP 942, ASTM, Philadelphia, PA, 1987, pp. 672–91.
J.W. Holmes and F.A. McClintock: inSuperalloys 1988, D.N. Duhl, G. Maurer, S. Antolovich, C. Lund, and S. Reichman, eds., TMS-AIME, Warrendale, PA, 1988, pp. 855–64.
J.W. Holmes and F.A. McClintock:Scripta Metall., 1983, vol. 17, pp. 1365–70.
M.M.P. Janssen and G.D. Rieck:Trans. TMS-AIME, 1967, vol. 239, pp. 1372–90.
G.W. Goward and D.H. Boone:Oxid. Met., 1971, vol. 3 (5), pp. 475–95.
O.W. Kriege and J.M. Bans:Trans. ASM, 1969, vol. 62, pp. 195–200.
E. Lang and L. Tottle: Reprint ofSome Observations Concerning the Stuctural Stability of Aluminide Coatings on IN738LC, Joint Research Establishment, Petten, The Netherlands, 1986.
Kevin O’Hara: General Electric Aircraft Engines, Lynn, MA, personal communication, Sept. 1986.
A.G. Evans, G.B. Crumley, and R.E. Demaray:Oxid. Met., 1983, vol. 20 (5/6), pp. 193–216.
G. Yurek: Massachusetts Institute of Technology, Cambridge, MA, private communication, 1986.
E. Busso: Master of Science Thesis, Massachusetts Institute of Technology, Cambridge, MA, Sept. 1986.
Touloukian, R.K. Kirby, R.E. Taylor, and T.Y.R. Lee:Thermophysical Properties of Matter, IFI/Plenum, New York, NY, 1979, vol. 13, p. 176.
G.V. Samsonov:The Oxide Handbook, Plenum, New York, NY, 1973, p. 183.
F.A. McClintock:Fracture of Solids, D.C. Drucker and J.J. Gilman, eds., 1963, pp. 65–102.
C.A. Berg and F.A. McClintock:Z. Angew. Math. Phys., 1966, vol. 17, pp. 453–56.
A. Taylor and R.W. Floyd:J. Inst. Met., 1952, vol.81, pp. 451–64.
O.W. Kriege and C.P. Sullivan:ASM Trans. Q., 1968, vol. 61, pp. 278–90.
Z. Meng, G. Sun, and M. Li: inSuperalloys 1984, M. Gell, C.S. Kortovich, R.H. Bricknell, W.B. Kent, and J.F. Radavich, eds., TMS-AIME, Warrendale, PA, 1984, pp. 563–72.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Holmes, J.W., McClintock, F.A. The chemical and mechanical processes of thermal fatigue degradation of an aluminide coating. Metall Trans A 21, 1209–1222 (1990). https://doi.org/10.1007/BF02698251
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF02698251