| Although metal materials have excellent wear resistance, their hardness、toughness and wear resistance cannot meet the requirements at the same time. Thus composite materials have emerged. As the most researched composites currently, particle reinforced metal matrix composites has many problems such as complicated preparation process、high production costs、weak interface bonding of the ceramic and metal matrix and uneven distribution of ceramic particles and so on. To solve these problems, the method of squeeze casting prepared ceramic particles reinforced high Cr cast iron wear-resistant parts was proposed in this paper. Systematic theoretical and experimental study were conducted from the aspects of process project、mold design、squeeze casting machine design、process exploration and the evaluation research of composites compound effect、microstructure and properties test.As the wear fillets for the vertical shaft crusher cone, the composite parts in this paper is wedge block with three rows imbedding hole,240*80*60mm in size, and the ceramic particles were ZTA (ZrO2 toughened Al2O3) of 2-4mm and 40% volume fraction, the mental matrix were micro-alloyed high-chromium cast iron KmTBCr26. The design of mold and squeeze casting machine were completed based on the technology named as "mixing by the molten metal and cohering by high pressures".Firstly, the feasibility experiments of squeeze casting ceramic particles/high Cr cast iron wear-resistant parts was conducted, proved that the process of "mixing by the molten metal and cohering by high pressures" is feasible. Secondly, a large number of experiments to study the influence of different process parameters on the parts forming and composite effect was carried out. when the main cylinder pressure at 700t, fill pressure cylinder pressure at 500t, pressure holding time at 12s, pack out cylinder pressure at 280t, speed is 100%, mental pouring temperature at 1600℃, ceramic particles preheating temperature at 1100℃, mold preheating temperature at 150-200℃, single-chamber particles quality at 2.3kg, particles height lower 3 mm than that of iron liquid height, the shape of runner is broadening formation, and placed 0.8mm baffle on particle chamber one side of near the pressure chamber, the better compound effect of composite parts was gained.The research of evaluation method on the wear-resistant parts compound effect was conducted, and proposed four evaluation indicators of mixing degree, partial poly degree, dispersion rate and combination rate to quantitative characterize the uniform degree of particle distribution, the particles reunion in the matrix and the combination of particle and matrix; the microstructure and hardness tests of composite parts were conducted, and the wear test in the condition of dry friction was carried out, the comparative investigations of the dry friction and wear properties between ZTA/KmTBCr26 composite and KmTBCr26 cast iron show clearly that wear resistance of the composite is 1.82 times higher than that of KmTBCr26 cast iron when the load is lower, while the wear resistance of the composite is increased to 3.3 times at high load. The impact fracture morphology of ZTA/KmTBCr26 composite was observed, found that the particles distribution in the ZTA/KmTBCr26 composite was generally uniform. Although the interfacial bonding between ceramic particle and KmTBCr26 matrix belongs to the micro-mechanic engaging, the fracture of composite is extending through the ceramic particle instead of the matrix, and it is not seen any particles detachment. So it is believed that the bonding strength between particle and matrix is larger than that of the matrix body. |
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