Thermal shock and erosion resistant tantalum carbide ceramic material

Ceramic tantalum carbide artifacts with high thermal shock and mechanical erosion resistance are provided by incorporating tungsten-rhenium and carbon particles in a tantalum carbide matrix. The mix is sintered by hot pressing to form the ceramic article which has a high fracture strength relative to its elastic modulus and thus has an improved thermal shock and mechanical erosion resistance. The tantalum carbide is preferable less than minus 100 mesh, the carbon particles are preferable less than minus 100 mesh, and the tungsten-rhenium particles are preferable elongate, having a length to thickness ratio of at least 2/1. Tungsten-rhenium wire pieces are suitable as well as graphite particles

Performance of rocket nozzle materials with several solid propellants

Erosion resistance and thermal stress cracking tests of rocket nozzle materials with solid propellant

Some considerations of the performance of two honeycomb gas path seal material systems

A standard Hastelloy-X honeycomb material and a pack aluminide coated honeycomb material were evaluated as to their performance as labyrinth seal materials for aircraft gas turbine engines. Consideration from published literature was given to the fluid sealing characteristics of two honeycomb materials in labyrinth seal applications, and their rub characteristics, erosion resistance, and oxidation resistance were evaluated. The increased temperature potential of the coated honeycomb material compared to the uncoated standard could be achieved without compromising the honeycomb material's rub tolerance, although there was some penalty in terms of reduced erosion resistance

Erosion of iron-chromium alloys by glass particles

The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping

Improved high pressure turbine shroud

A new high pressure turbine shroud material has been developed from the consolidation of prealloyed powders of Ni, Cr, Al and Y. The new material, a filler for cast turbine shroud body segments, is called Genaseal. The development followed the identification of oxidation resistance as the primary cause of prior shroud deterioration, since conversion to oxides reduces erosion resistance and increases spalling under thermal cycled engine conditions. The NICrAlY composition was selected in preference to NIAL and FeCRALY alloys, and was formulated to a prescribed density range that offers suitable erosion resistance, thermal conductivity and elastic modulus for improved behavior as a shroud

Advanced fiber-composite hybrids--A new structural material

Introduction of metal foil as part of matrix and fiber composite, or ""sandwich'', improves strength and stiffness for multidirectional loading, improves resistance to cyclic loading, and improves impact and erosion resistance of resultant fiber-composite hybrid structure

Erosion of gadolinia doped EB-PVD TBCs

Gadolinia additions have been shown to significantly reduce the thermal conductivity of EB-PVD TBCs. The aim of this paper is to further the understanding on the effects of dopants on the erosion resistance of EB-PVD TBCs by studying the effects of 2 mol% Gd2O3 additions on the room and high temperature erosion resistance of as received and aged EB-PVD TBCs. Previously it has been reported that gadolinia additions increased the erosion rate of EB- PVD TBCs, this is indeed the case for room temperature erosion, however under high temperature (825 à °C) erosion conditions this is not the case and the doped TBCs have a slightly lower erosion rate than the standard YSZ EB-PVD TBCs. This has been attributed to a change in the erosion mechanisms that operate at the different temperatures. This change in mechanism was not expected under the impact conditions used and has been attributed to a change in the column diameter, and how this influences the dynamics of particle impactio

Effects of erodant particle shape and various heat treatments on erosion resistance of plain carbon steel

Erosion tests were conducted on 1045 steel samples which had been subjected to different heat treatments. The weight of material removed upon erosion with glass beads and crushed glass was measured. The data show that there is no correlation between hardness and erosion resistance. The erosion rate was strongly dependent on the shape of erodant particles, being an order of magnitude higher for erosion with crushed glass than with glass beads. Heat treatment had a profound effect on the erosion resistance when the erodant particles were glass beads but little or no effect when the particles were crushed glass. It is thus concluded that different mechanisms of material removal are involved with these two erodants. This conclusion is supported by the surface morphology of annealed 1045 steel samples which had been eroded by these two types of erodant particles. SEM micrographs of the eroded surfaces show that for erosion with glass beads it is deformation induced fracture of surface layers

Sealing technology for aircraft gas turbine engines

Experimental evaluation under simulated engine conditions revealed that conventional mainshaft seals have disadvantages of high gas leakage rates and wear. An advanced seal concept, the self-acting face seal, has a much lower gas leakage rate and greater pressure and speed capability. In endurance tests (150 hr) to 43 200 rpm the self-acting seal wear was not measurable, indicating noncontact sealing operation was maintained even at this high rotative speed. A review of published data revealed that the leakage through gas path seals has a significant effect on TSFC, stall margin and engine maintenance. Reducing leakages by reducing seal clearances results in rubbing contact, and then the seal thermal response and wear determines the final seal clearances. The control of clearances requires a material with the proper combination of rub tolerance (abradability) and erosion resistance. Increased rub tolerance is usually gained at the expense of reduced erosion resistance and vice versa

Development of sprayed ceramic seal systems for turbine gas path sealing

A ceramic seal system is reported that employs plasma-sprayed graded metal/ceramic yttria stabilized zirconium oxide (YSZ). The performance characteristics of several YSZ configurations were determined through rig testing for thermal shock resistance, abradability, and erosion resistance. Results indicate that this type of sealing system offers the potential to meet operating requirements of future gas turbine engines