Constrained sintering of YSZ/Al2O3 composite coatings on metal substrates produced from eletrophoretic deposition

Abstract Yttria stabilized zirconia/alumina (YSZ/Al2O3) composite coatings were prepared from electrophoretic deposition (EPD), followed by sintering. The constrained sintering of the coatings on metal substrates was characterized with microstructure examination using electron microscopy, mechanical properties examination using nanoindentation, and residual stress measurement using Cr3+ fluorescence spectroscopy. The microstructure close to the coating/substrate interface is more porous than that near the surface of the EPD coatings due to the deposition process and the constrained sintering of the coatings. The sintering of the YSZ/Al2O3 composite coating took up to 200 h at 1250 °C to achieve the highest density due to the constraint of the substrate. When the coating was sintered at 1000 °C after sintering at 1250 °C for less than 100 h, the compressive stress was generated due to thermal mismatch between the coating and metal substrate, leading to further densification at 1000 °C because of the ‘hot pressing’ effect. The relative densities estimated based on the residual stress measurements are close to the densities measured by the Archimedes method, which excludes an open porosity effect. The densities estimated from the hardness and the modulus measurements are lower than those from the residual stress measurement and the Archimedes method, because it takes account of the open porosity.

[1]  G. Lu,et al.  Constrained‐Film Sintering of a Borosilicate Glass: In Situ Measurement of Film Stresses , 1995 .

[2]  R. Raj,et al.  Flaw Generation During Constrained Sintering of Metal-Ceramic and Metal–Glass Multilayer Films , 1989 .

[3]  G. Lu,et al.  Constrained-film sintering of cordierite glass-ceramic on silicon substrate , 1998 .

[4]  I. Chen,et al.  Sintering dense nanocrystalline ceramics without final-stage grain growth , 2000, Nature.

[5]  H. Bowen,et al.  Kinetics of Constrained‐Film Sintering , 1990 .

[6]  Yung-Chiang Lin,et al.  Constrained Densification Kinetics of Alumina/Borosilicate Glass + Alumina/Alumina Sandwich Structure , 2004 .

[7]  H. Riedel,et al.  Equilibrium pore surfaces, sintering stresses and constitutive equations for the intermediate and late stages of sintering—I. computation of equilibrium surfaces , 1994 .

[8]  James F. Shackelford,et al.  The CRC Materials Science And Engineering Handbook , 1991 .

[9]  P. Xiao,et al.  Fabrication of ceramic composite coatings using electrophoretic deposition, reaction bonding and low temperature sintering , 2002 .

[10]  P. Xiao,et al.  Residual stresses and constrained sintering of YSZ/Al2O3 composite coatings , 2004 .

[11]  J. A. Thompson,et al.  THE EFFECT OF HEAT TREATMENT ON THE STIFFNESS OF ZIRCONIA TOP COATS IN PLASMA-SPRAYED TBCs , 2001 .

[12]  L. Lorenzoni,et al.  Studies of the sintering kinetics of thick thermal barrier coatings by thermal diffusivity measurements , 2005 .

[13]  A. F. Renteria,et al.  Effect of ageing on microstructure changes in EB-PVD manufactured standard PYSZ top coat of thermal barrier coatings , 2006 .

[14]  Robert A. Miller,et al.  Current status of thermal barrier coatings — An overview , 1987 .

[15]  K. Peng,et al.  Electrophoretic deposition of porous hydroxyapatite scaffold. , 2003, Biomaterials.

[16]  W. D. Kingery,et al.  Introduction to Ceramics , 1976 .

[17]  J. Jean,et al.  Stress development during constrained sintering of alumina/glass/alumina sandwich structure , 2004 .

[18]  R. Raj,et al.  Sintering Behavior of Ceramic Films Constrained by a Rigid Substrate , 1985 .

[19]  P. Xiao,et al.  Nanoindentation and residual stress measurements of yttria-stablized zirconia composite coatings produced by electrophoretic deposition , 2006 .

[20]  S. Guo,et al.  Effect of thermal exposure on hardness and Young's modulus of EB-PVD yttria-partially-stabilized zirconia thermal barrier coatings , 2006 .

[21]  Jianlin Shi,et al.  Relation Between Coarsening and Densification in Solid-state Sintering of Ceramics: Experimental Test on Superfine Zirconia Powder Compacts , 1999 .

[22]  J. Rödel,et al.  Cosintering Simulation and Experimentation: Case Study of Nanocrystalline Zirconia , 2001 .

[23]  O. Guillon,et al.  Anisotropic constitutive laws for sintering bodies , 2006 .

[24]  E. Winn,et al.  Microstresses in particulate-reinforced brittle composites , 2001 .

[25]  Jianlin Shi,et al.  Thermodynamics and Densification Kinetics in Solid-state Sintering of Ceramics , 1999 .

[26]  E. Jordan,et al.  Thermal Barrier Coatings for Gas-Turbine Engine Applications , 2002, Science.

[27]  D. Clarke,et al.  Residual Stresses in Alumina/Ceria‐Stabilized Zirconia Composites , 1995 .

[28]  Anthony G. Evans,et al.  Mechanisms controlling the durability of thermal barrier coatings , 2001 .

[29]  J. Rödel,et al.  Critical Evaluation of Hot Forging Experiments: Case Study in Alumina , 2003 .

[30]  K. Schlichting.  Failure modes of plasma-sprayed thermal barrier coatings , 2003 .

[31]  David J. Green,et al.  An Introduction to the Mechanical Properties of Ceramics , 1998 .

[32]  D. Clarke,et al.  Wrinkling of α-alumina films grown by thermal oxidation—I. Quantitative studies on single crystals of Fe–Cr–Al alloy , 1998 .

[33]  R. McPherson,et al.  A review of microstructure and properties of plasma sprayed ceramic coatings , 1989 .

[34]  A. Fahmy,et al.  Thermal‐Expansion Behavior of Two‐Phase Solids , 1970 .

[35]  R. Raj.  Analysis of the sintering pressure , 1987 .

[36]  J. S. Reed,et al.  Principles of ceramics processing , 1995 .

[37]  A. Tsoga,et al.  Surface and grain-boundary energies in yttria-stabilized zirconia (YSZ-8 mol%) , 1996 .

[38]  A. Jagota,et al.  Crack Growth and Damage in Constrained Sintering Films , 1993 .

[39]  G. Lu,et al.  Constrained-film sintering of a gold circuit paste , 1995 .

[40]  G. Pharr,et al.  An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments , 1992 .

[41]  F. P. Knudsen.  Dependence of Mechanical Strength of Brittle Polycrystalline Specimens on Porosity and Grain Size , 1959 .

[42]  R. M. Spriggs.  Expression for Effect of Porosity on Elastic Modulus of Polycrystalline Refractory Materials, Particularly Aluminum Oxide , 1961 .