Relations between Mechanical Properties of Thermal-Sprayed Ceramic Coatings and Substrate Temperature during Deposition

Abstract

Thermal spraying is widely used in various industrial fields as effective surface modification method. However, the coating failures such as cracking, debonding and spallation occur due to external loading or internal stress induced by the mismatch of material properties between coating and substrate, and these become a major problem. In this study, mechanical properties of thermal-sprayed ceramic coatings were investigated. Al 2 O 3 and Y 2 O 3 -stabilized ZrO 2 (YSZ) coatings were deposited on plate substrates. Stainless steel plates and aluminum plates, of different thermal expansion coefficients, were used as substrates. The coatings were prepared at two different thicknesses. During deposition of each specimen, the history of substrate temperature was recorded. Four-point bending tests were carried out, while strains at the coating surface and the substrate surface were measured with strain gages. The apparent Young's modulus of the coating was determined using the composite beam theory. Subsequently, the rupture strain of the coating was measured by a three-point bending test. In addition, the residual stresses of the coating were determined by mechanical polishing. The relationships between the results of these tests and the each substrate temperatures during deposition were discussed.

Effects of High-Temperature Exposure on Mechanical Properties of Thermal Sprayed CoNiCrAlY Alloy Coating

“…Concerning residual stresses of coatings, establishment of a numerical model was reported focusing on residual stress distribution in direction of thickness (2) - (4) , and many researches about fracture of coating such as cracking and delamination were reported using various test methods (5) - (7) . Authors have reported about mechanical properties of thermal sprayed ceramic coatings related with substrate temperature during deposition (8) .…”