Thermal Fatigue Life Prediction of Ni Base Alloy Ceramic Composite Coating

Abstract

Ni base alloy ceramic grain composite coating is used mostly in high temperature condition, so thermal fatigue failure will be easy. If the thermal expansion coefficients and elastic modulus of Ni base alloy and ceramic grain are different, there will be thermal stresses between grain and matrix in thermosyphon. The thermal stress will arouse the initiation and growth of thermal fatigue crack. We use Eshebly-Mori-Tanaka method to study the thermal stress field in matrix and grain. It can be shown that the more difference of thermal expansion coefficients between Ni base alloy and ceramic grain is, the bigger the thermal stress is. The thermal stress relates to volume fractions and elastic constants of Ni base alloy and ceramic grain. Based on low-cycle fatigue crack growth rate formation, the thermal fatigue life was computed. The bigger thermal stress is, the smaller thermal fatigue life is. Thermal life is an exponential function of crack initiation length and critical length.

Thermal Expansion Coefficient of Ni Base Alloy Composite Coating Containing Spheroidal Ceramic Grains

“…Ni base alloy is of good heat-resisting ability, it is mostly applied in the engine of airplane, the turbojet and the nuclear reactor [1]. Ni base alloy ceramic composite coating containing spheroidal ceramic grains fabricated through vacuum fusion sintering process can acquire high strength and good thermal fatigue resistance [2,3]. The composite coating is a mechanical disordered composite; a large number of spheroidal ceramic grains are distributed in Ni base alloy matrix.…”

The Micromechanical Stress Field of Cermets Composite Containing Interfacial Arc-Microcracks

“…As the micromechanical structures are stochastic, indeterminate and evolutionary, many intercoupling methods are advanced in recent 40 years based on non-intercoupling method, including PCW method [2], Mori-Tanaka method [3] , and the explicit and universally applicable IDD method given by Zheng et al [4]. Mori-Tanaka method could predict the effective elastic modulus and thermal Fatigue Life of Ni based alloy ceramic grain composite [5,6]. Considering the random orientation of arc-microcrack, we use Mori-Tanaka method to determine the average disturbance strain.…”

Residual Stress Field of Ellipsoidal Ceramic Particles Ni-Base Alloy Composite Coating

“…Ni base alloy ceramic composite coating can be fabricated by a vacuum fusion sintering method [2]. Ni base alloy ceramic composite coating is a mechanic disordered composite [3], a large number of ceramic grains are distributed in ductile matrix. The experiments show that cracks produce mostly between ceramic particles and Ni base alloy matrix and grow mostly along boundary of phases.…”