A segmented abradable ceramic coating system having superior abradability and erosion resistance is disclosed. The system includes a duct segment having a metallic substrate, a MCrAlY bond coat on the substrate and a segmented abradable ceramic coating on the bond coat. The segmented abradable ceramic coating includes a base coat foundation layer, a graded interlayer and an abradable top layer for an overall thickness of preferably about 50 mils (1.270 mm). The coating is characterized by a plurality of vertical microcracks. By precisely controlling the deposition parameters, composition of the layers and layer particle morphology, segmentation is achieved, as well as superior abradability and erosion resistance.

Segmented abradable ceramic coating

Elastic modulus of plasma-sprayed coatings determined by indentation and bend tests

A method of producing a segmented abradable ceramic coating system having superior abradability and erosion resistance is disclosed. The system includes a duct segment having a metallic substrate, a MCrAlY bond coat on the substrate and a segmented abradable ceramic coating on the bond coat. The segmented abradable ceramic coating includes a base coat foundation layer, a graded interlayer and an abradable top layer for an overall thickness of preferably about 50 mils (1.270 mm). The coating is characterized by a plurality of vertical microcracks. By precisely controlling the deposition parameters, composition of the layers and layer particle morphology, segmentation is achieved, as well as superior abradability and erosion resistance.

Method of producing a segmented abradable ceramic coating system

This study evaluated the Young's modulus, residual stress and strain, bonding strength, and microstructure of the plasma-sprayed hydroxyapatite coating (HAC) on Ti6Al4V substrate with and without immersion in Hank's balanced salt solution (HBSS). The purpose was to explore the possible correlation of HAC durability and mechanical properties of the coating. The results show that the residual stress and strain, Young's modulus, and bonding strength of the HAC after immersion in HBSS are substantially decreased. The decayed Young's modulus and mechanical properties of HACs are accounted for by the degraded interlamellar or cohesive bonding in the coating due to the increased porosity after immersion that weakens the bonding strength of coating and substrate system. The biologic implications of the research are discussed in detail. This study contributes to the arguments that the method to alleviate the dissolution of HAC will increase the bonding strength of the coating system after immersion, which together with the controlled residual stress and strain in the coating might promote the long-term stability of the HA-coated implant. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 886–899, 2003

Mechanical properties and Young's modulus of plasma-sprayed hydroxyapatite coating on Ti substrate in simulated body fluid.

Much research has been performed in the field of thermal barrier coatings (TBCs) deposited by atmospheric plasma spraying of ZrO2-Y2O3. The necessity of efficient thermal insulation, corrosion resistance, and sufficient lifetime under thermomechanical loads promotes the development of TBCs of several millimeters in thickness. However, some problems arise with the production of thick TBCs, such as poor adhesion and low thermal shock resistance. These problems are not observed clearly when the TBCs are, for example, 300 µm thick. This article presents strategies of thick TBC lifetime optimization by different cooling systems. Attempts have been made to improve thermal shock resistance (TSR) by applying thicker coatings with graded porosity, but they failed. Besides metallographical evaluation and scanning electron microscopy (SEM) analysis, microcracks and porosity were determined. Furthermore, the results of bond strength and burner rig tests are presented, and forthcoming experimental tasks are outlined.

Some aspects of thick thermal barrier coating lifetime prolongation

Thirty three plasma spray runs of ZrO2 (with 20% Y2O3) were made in which processing parameters were intentionally varied. Strength and modulus were measured using four-point bend testing. Strength values ranging from 2110 to 7690 lbf in-2 and modulus values ranging from 2.88 to 6.80 Mlbf in-2 were observed. An elementary model was developed to predict the strength and modulus based on the powder particle heating and acceleration as well as the residual stress of the substrate and the thermal shock induced during spraying. The model explains 88% of the variation in strength values and 72% of the variation in modulus values.

H.E. Eaton

Papers

A study of the effects of variations in parameters on the strength and modulus of plasma sprayed zirconia