| Hydraulic impact hammer is a main working part of rotary drilling system widely used inthe field of hard rock drilling. Due to poor working conditions, severe abrasion of the pistoncylinder liner greatly reduces the service life of the impact hammer, and directly impacts on thedrilling efficiency. It is the focus of researchers that improving the abrasion resistanceperformance of the hydraulic impact hammer piston cylinder liner. In accordance with theabrasion form of the hydraulic impact hammer piston cylinder liner, a technology forimproving the abrasion resistance performance and a preparation process of a bionic surfaceare researched based on a combination of experiments and numerical simulations in this paper.The bionic model used in this paper is scapharca subcrenata which lives in the siltenvironment. The scapharca subcrenata shell surface model was established using reverseengineering technology （the software Geomagic studio）, and the numerical simulation of themultiphase flow field of the scapharca subcrenata shell surface was conducted by coupling ofEDEM and FLUENT. Based on the results above, we explored the abrasion resistancemechanism of the scapharca subcrenata shell surface. An analysis of the contour curves of thescapharca subcrenata is carried out using the software GetData Graph Digitizer, and the pointdata extracted was curve fitted by the software MATLAB, so both the trigonometric functionequation and the unit bionic model are acquired respectively. The hardness distribution of thescapharca subcrenata shell surface is measured by micro-hardness tester. The result showedthat the scapharca subcrenata shell surface appears hard alternate with soft structures. Impairedby the structures, a coupling bionic model was established.The experimental research of the abrasion resistance performance of the bionic samplewere carried out in this paper by the test optimization design theory and the coupling theory ofEDEM and FLUENT. We carried out an abrasion resistance test for the bionic sample and thecoupling bionic sample using a mixed orthogonal table of L9（21×33）, the results showed thatthe primary and secondary factors in the order affecting the relative abrasion rate of testing samples were the Laser Surface Strengthening Technology（D）, the amplitude（B）, the cycletime（C） and the direction of stripes（A）. From the abrasion resistance performance analysis ofthe three samples we can see the abrasion resistance performance of the coupling bionic sample,the unit bionic sample and the smooth scapharca subcrenata shell surface sample weakened inturn. Based on the conditions of this experiment, the abrasion resistance performance of thenormal stripes is superior to that of the tangential stripes.The multiphase flow field of the bionic sample and the smooth sample surfaces werenumerical simulation by EDEM and FLUENT, the water-sand multiphase flow information andthe behavior of the sand grains on the bionic surface were obtained. The abrasion resistancemechanism of the bionic sample was preliminary analyzed that the ribbed structure of thesample with the stripe bionic surface changes the movement direction of the sand grains. Thelow-speed fluid in the groove structures weaken the impact of particles to the wall surface, andalso protect the material of the recess in the sample. The strengthening treatment ribbedstructures as a larger part of the model help to further improve the erosion resistance of thecoupling bionic sample.A preparation process of the bionic abrasion-resistant surface for20CrMnTi wasresearched in this paper. The test parameters of the laser processing were optimized using thetest optimization design method. To get laser alloying optimal combination of parameters forpeak power0.657kW, the pulse width4ms, scanning speed1.5mm·s-1, frequency6Hz, defocusamount7mm, laser transformation hardening optimal combination of parameters for peakpower0.974kW, the pulse width of4ms, scanning speed2.0mm·s-1, frequency4Hz, defocusamount7mm. We find surface depression, internal pores and cracks that existed in some weldpools are caused by the surface material splashing or vaporization due to the high density oflaser energy. The microhardness values before and after the laser processing were measured, itshowed that the microhardness of laser alloying treatment sample had a significantimprovement. By observation of the microstructure of the material, we found grain refinementand an increase of needle-like martensite. Considering the factors such as laser surfacehardening technology, enhanced with shape, width or spacing, we processed a bionic hammerpiston sample. |
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