Microstructure of plasma sprayed Al2O3-3wt% TiO2 coating using freeze granulated powder

Microstructure of plasma sprayed Al2O3-3wt% TiO2 coating using freeze granulated powder

Yiming Yao, Ola Lyckfeldt, Aurélien Tricoire, Dennis Lundström, Uta Klement

Abstract

This study is aiming at controlling the microstructure of plasma sprayed Al2O3-TiO2 composite coatings using freeze granulated powders. As sprayed and sintered Al2O3 + 3wt% TiO2 powders were air plasma sprayed with industry process parameters and compared with a commercial powder. The resulting coatings were investigated with respect to powder flowability, porosity and microstructure of the granules. The results showed that microstructure and melting fraction in the coatings could be tailored with the freeze granulation process and heat treatment conditions.

Keywords

Al2O3-TiO2, Freeze Granulation, Plasma Spray, Microstructure

Additive-free hot-pressed silicon carbide ceramics-A material with exceptional mechanical properties

Additive-free hot-pressed silicon carbide ceramics-A material with exceptional mechanical properties

P. Šajgalík, J. Sedláček, Z. Lenčéš, J. Dusza, H.-T. Lin

Abstract

Densification of silicon carbide without any sintering aids by hot-pressing and rapid hot pressing was investigated. Full density (>99% t.d.) has been reached at 1850 °C, a temperature of at least 150–200 °C lower compared to the up to now known solid state sintered silicon carbide powders. Silicon carbide was freeze granulated and heat treated prior the densification. Evolution of microstructure, mechanical properties and creep behavior were evaluated and compared to reference ceramics from as received silicon carbide powder as well as those of commercial one. Novel method results in dense ceramics with Vickers hardness and indentation fracture toughness of 29.0 GPa and 5.25 MPa m1/2, respectively. Moreover, the creep rate of 3.8 × 10−9 s−1 at 1450 °C and the load of 100 MPa is comparable to the commercial α-SiC solid state sintered at 2150 °C.

Keywords

Silicon carbide, Hot pressing, Microstructure, Mechanical properties, Creep resistance, freeze granulation