Effect of infiltrated eutectic AlSi on the microstructure and properties of C/C composites

Eutectic AlSi alloy was pressure infiltrated into a porous C/C skeleton to develop a low cost new C/C composite for application without extreme high temperature. C/C composite possessed a density of 1.7 g/cm3 was prepared for comparison. The effects of filling AlSi with and without Al-Ti-C grain refiner on the microstructure and properties of C/C composites were mainly studied. Result indicated that the introduced AlSi interpenetrated with C/C skeleton and made the composites compact. In comparison with C/C composite, the compressive strength and particle erosion resistance were greatly enhanced while the density and thermal expansion coefficient (CTE) increased slightly. After adding the refiner, Si network involved dendritic Al in C/C-AlSi was transformed to refined mixed AlSi, Al bulk and Si surrounded dendritic Al, and two kinds of micro-cracks came into being, which resulted in the decreased strength, improved erosion property and increased CTE of C/C-AlSiR. Both AlSi textures and micro-cracks in the modified C/C composites determined the crack propagation and led to their different compressive behaviors and anti-erosion abilities.

Alternative Design of Double-Suction Centrifugal Pump to Reduce the Effects of Silt Erosion

Large amounts of sediment in the Himalayan rivers causes severe silt erosion to the hydraulic machinery operating along these rivers. In this study, the effects of silt characteristics on the silt-erosion characteristics of a double-suction centrifugal pump was studied and the anti-erosion property of bionic convex domes on silt erosion under these conditions was explored by using computational-fluid-dynamics methods, partly supported by a painted-blade erosion experiment. The results show that the silt size affects the erosion position and erosion strength, whereas the silt concentration mainly affects the erosion strength for the studied range. The bionic convex domes provide an effective solution to improve the silt erosion for most of the investigated silt-laden conditions by decreasing the erosion rate and the erosion area of the blade. The anti-erosion mechanism was studied combined with large eddy simulation. The analysis shows that the relative velocity of water around the blade surface is changed and the mass flow rate of silt particles hitting the blade is reduced by inducing swirling flows around the bionic convex domes.

Biomimetic Design and Manufacturing of Anti-Erosion Functional Surfaces Inspired from Desert Scorpion

Sand erosion is a phenomenon that solid particles impinging to a wall cause serious mechanical damages to its surface. It's tough to be a machine in the desert: particles of dirt and sand work their way into moving parts, where they abrade helicopter propellers, airplane rotor blades, pipes and other equipments. However, the desert scorpion (Androctonus australis) live their entire lives subjected to blowing sand, yet they never appear to be eroded. In this study, the anti–erosion characteristic rules of the scorpion surfaces under aerodynamics effect of gas/solid mixed media were studied. Biomimetic linear–cutted surfaces consisting of an array of three types of grooves, square–type, V–type and U–type, were designed and investigated to quantify their erosion wear resistance properties. A smooth surface sample was fabricated for comparison. The ANSYS-Fluent simulation of biomimetic models showed that the V-type groove sample, inspired by the desert organism's surface with different morphologies, exhibited the best erosion resistance. It also indicated the anti-erosion property of biomimetic samples could be attributed to the rotating flow in the grooves that reduces the impact speed of particles. The synchronized erosion test confirmed the conclusions. Furthermore, an application exploring of bionic blades on a centrifugal fan was conducted. The blades with optimum parameters could effectively improve anti-erosion property by 29%. We envision that more opportunities for biomimetic application in improving the anti–erosion performance of parts that work under dirt and sand particle environment will be proposed.

Study of drilling muds on the anti-erosion property of a fluidic amplifier in directional drilling

Due to some drawbacks of conventional drilling methods and drilling tools, the application of hydraulic hammers with a fluidic amplifier have been extensively popularized since its emergence in recent years. However, the performance life of a fluidic amplifier is still unsatisfactory in oil and gas wells drilling, especially the heavy wear or erosion of the fluidic amplifier leads to the reduction of service life time of hydraulic hammers, which is derived from the incision of drilling muds with high speed and pressure. In order to investigate the influence of drilling muds, such as particle size, solid content and jet velocity, on the antierosion property of a fluidic amplifier, several groups of drilling muds with different performance parameters have been utilized to numerical simulation on basis of Computational Fluid Dynamics (CFD). Simulation results have shown that the jet nozzle of fluidic amplifiers is primarily abraded, afterwards are the lateral plates and the wedge of the fluidic amplifier, which shows extraordinary agreement with the actual cases of fluidic amplifier in drilling process. It can be concluded that particle size, solid content and jet velocity have a great influence on the anti-erosion property of a fluidic amplifier, and the erosion rate linearly varies with the particle size of drilling muds, nevertheless exponentially varies with solid content and jet velocity of drilling muds. As to improve the service life time of a fluidic amplifier, the mud purification system or low solid clay-free mud system is suggested in the operation of directional well drilling.

Study on Preparing Coating for the Anti-Erosion Property of Artillery

To enhance anti-erosion property of artillery barrel and prolong the using period of the artillery, some new technologies are summarized and discussed in this paper, which including electric explosion spraying technology, hypersonic flame spraying technology and plasma surfacing. The experimental results show that the electric explosion spraying technology is a feasible method to prepare coating for the anti-erosion property of 100mm diameter artillery barrel.