Tailored thermal barrier coatings deposited by hybrid water-stabilized plasma torch

High enthalpy plasma generated by hybrid water-stabilized plasma (WSP-H) torch enables spraying of dry powders, suspensions as well as solutions with superior feed rates, which makes this technology ideal for cost-effective spraying of thick and/or large-area coatings. Moreover, the versatility of the deposition process enables individual tailoring of the coatings compositions, microstructures and properties for various novel applications. In this study, feasibility of high throughput deposition of TBCs with WSP-H technology will be illustrated for selected model materials (e.g., YSZ, Gd2Zr2O7, YAG) deposited from conventional powders as well as from liquid feedstocks. Application-relevant properties of these coatings (thermal conductivity, wear resistance, mechanical properties, high-temperature behavior, etc.) will be discussed and related to the wide range of achievable microstructures (see figures below for illustration). Examples of perspective multiphase coatings having layered, intermixed or functionally graded microstructures will be also provided. Please click Additional Files below to see the full abstract

COMPACTION OF LITHIUM-SILICATE CERAMICS USING SPARK PLASMA SINTERING

This paper deals with the compaction of ceramics based on lithium-silicate by spark plasma sintering (SPS). The initial powder was prepared by calcination in a resistance furnace at a temperature of 1300 °C with the ratio of Li/Si = 1. Compacting by SPS was carried out at temperatures of 800 - 1000 °C with a maximum pressure of 80 MPa. Samples with open porosity of less than 1 % were prepared at the temperature of 1000 °C. According to the quantitative Rietveld refinement of x-ray diffraction data, the dominant phases in all samples were Li₂Si₂O₅ and Li₂SiO₃, together representing over 80 wt. % of the sintered material

Thermophysical properties of YSZ and YCeSZ suspension plasma sprayed coatings having different microstructures

International audienc

The microstructural studies of suspension plasma sprayed zirconia coatings with the use of high-energy plasma torches

International audienc

Influence of processing conditions on the microstructure and sliding wear of a promising Fe-based coating deposited by HVAF

Thermal spray is a versatile and cost-effective process to deposit wear and corrosion resistant coatings. In this work, a relatively new ‘Fe-based’ chemistry comprising boride and carbides, is explored as a ‘greener’ alternative to the relatively expensive and carcinogenic Co-based coatings to mitigate wear. The emergent thermal spray process of high-velocity air-fuel (HVAF) spraying was chosen to deposit the Fe-based coatings, with the high-velocity oxy-fuel (HVOF) also being employed solely for the purpose of preliminary comparison. Detailed characterization of the HVOF and HVAF sprayed Fe-based coatings was carried out. Microstructure, porosity, hardness and phase analysis results demonstrate the influence of processing conditions, where specific spray conditions yielded minimal undeformed particulates content, high hardness, low porosity and feedstock phase retention. Differences in microstructural features of the as-deposited coatings in relation to their processing conditions are discussed in detail. The coatings were subjected to ball-on-disc tribometry tests at different load conditions and their friction and wear performance were evaluated. The coefficient of friction results of investigated coatings concurred with their respective microstructural features. Post-mortem of the worn coating surface, the mating alumina ball surface and wear debris was performed using SEM/EDS analysis to understand the associated wear mechanisms and material transfer. This work provides new insights on identifying appropriate HVAF processing conditions to achieve acceptable microstructural features and phases in Fe-based coatings for improved wear performance