Evaluating high temperature elastic modulus of ceramic coatings by relative method

Abstract

Abstract:The accurate evaluation of the elastic modulus of ceramic coatings at high temperature (HT) is of high significance for industrial application, yet it is not easy to get the practical modulus at HT due to the difficulty of the deformation measurement and coating separation from the composite samples. This work presented a simple approach in which relative method was used twice to solve this problem indirectly. Given a single-face or double-face coated beam sample, the relative method was firstly used to determine the real mid-span deflection of the three-point bending piece at HT, and secondly to derive the analytical relation among the HT moduli of the coating, the coated and uncoated samples. Thus the HT modulus of the coatings on beam samples is determined uniquely via the measured HT moduli of the samples with and without coatings. For a ring sample (from tube with outer-side, inner-side, and double-side coating), the relative method was used firstly to determine the real compression deformation of a split ring sample at HT, secondly to derive the relationship among the slope of load-deformation curve of the coated ring, the HT modulus of the coating and substrate. Thus, the HT modulus of ceramic coatings can be evaluated by the substrate modulus and the load-deformation data of coated rings. Mathematic expressions of those calculations were derived for the beam and ring samples. CVD-SiC coatings on graphite substrate were selected as the testing samples, of which the measured modulus ranging from room temperature to 2100 ℃ demonstrated the validity and convenience of the relative method.

Influence of Preheating on the Microstructure Evolution of Laser Re-Melting Thermal Barrier Coatings/Ni-Based Single Crystal Superalloy Multilayer System

“…The residual APS coatings remain the lamellar structure with massive inter-splats pores and interior voids. The as-sprayed coatings consist of a lamellar structure with massive inter-splat pores and interior voids, which have an approximate 50% reduction in in-plan elastic modulus with respect to the bulk materials [52,53,54,55]. While the laser re-melting can eliminate these pores to develop a dense re-melted layer, when heating or cooling, the four layers will suffer the thermal mismatch stress due to the inter-layer deformation constraints.…”

Low thermal conductivity and anisotropic thermal expansion of ferroelastic (Gd1−xYx)TaO4 ceramics

“…E is a physical quantity related to the resistance of the material to deformation, and can also characterize the bonding strength of the material [49,50]. During the operation of the turbine engine, it will be hit by some foreign objects, which will cause cracks in the coating and eventually damage [51].…”

High temperature mechanical retention characteristics and oxidation behaviors of the MoSi2(Cr5Si3)—RSiC composites prepared via a PIP—AAMI combined process

“…A batch of five specimens were tested and the obtained values were averaged. Specimens with the size of 3 mm × 4 mm × 50 mm were used to measure the three-point flexural strength (σ f ) and elastic modulus (E f ) with a span of 30 mm and a loading rate of 0.5 mm•min -1 [1,38]. The fracture toughness (K IC ) of the as-prepared samples was measured by the single-edge-notched-beam (SENB) method, the size of the specimens was 4 mm (height) × 2 mm (width) × 35 mm (length) with a span of 15 mm and a loading velocity of 0.5 mm•min -1 , and the notches were incised www.springer.com/journal/40145 in the middle of the samples along the height using a circular saw with a width of 0.3 mm to the depth of 1-1.5 mm [39].…”