Study On The Preparation And Properties Of Coarse Grained TiC-High Manganese Steel Bonded Carbides

TiC-high manganese steel bonded carbides as a kind of excellent abrasion resistance and anti-wear material, commonly used in key parts of wear component to improve its performance and life, has become an important development direction of high-performance wear-resistant parts production. The practical use show that the steel bonded carbide wear-resisting block used currently has its drawbacks such as large brittleness, fracture phenomenon and falls off phenomenon. Its wear-resisting performance has reached a balance, to further improve the comprehensive mechanical properties became an urgent practical need. In this paper, the particle size of hard phase TiC was taked as a starting point, to explore that through coarse grain change to solve existing problems, and the preparation technology and alloy performance were systematically studied as well.In the aspect of exploring the influence of ball mill process on the properties and organization of coarse grained TiC-high manganese steel bonded carbides,the dry grinding of raw material TiC and the wet grinding of alloy mixture,which used rolling ball mill,were studied and analyzed with the microstructure and mechanical properties of sintered alloy.The experimental results show that:1)TiC is typical brittle hard materials,as dry milling time increases,large pieces of TiC particles was quickly broken with the other certain dry grinding parameters steady.Volume fracture was the main refinement mechanism at the early stage of dry grinding,while surface fracture was the main refinement mechanism at the late stage of dry grinding.The best dry milling time was 3h with the D50 of TiC powder about 8?m in the experiment.2)Wet milling speed should be reduced to 0.65n??to avoid excessive refinement of coarse particle TiC material in the process of wet milling for the purpose to get priority of mixture over crushing.With the extension of wet milling time,there were less pore in the microstructure after sintering and the distribution of hard phase in the matrix was more uniform,and the corresponding mechanical properties such as flexural strength,impact toughness and hardness increased rapidly.The best wet milling time was 21h with the flexural strength about 1481MPa,impact toughness about 2.64J/cm2 and rockwell hardness about 65HRC in this phase of the experiment.In the aspect of exploring compacting molding and quality control of mixture, vacuum sintering and subsequent water toughening treatment, the suppressing curve of mixture and the influence of compact on the quality and performance of sintered metal were studied using the binder SBS. Change law and mechanism of atmosphere pressure in sintering furnace were studied, and its influence on performance and organization of alloy was analyzed. The law of function of water toughening treatment under temperature of 1050? on coarse grained TiC-high manganese steel bonded carbides was researched. Study found that: 1) Suppressing pressure indirectly affected the final density and rockwell hardness of the sintered alloy through the influence on quality and density of the compact. When pressing pressure exceeded 300 MPa, density and rockwell hardness of the sample tend to be stable, with the density about 6.05g/cm3 and the Rockwell hardness about 65 HRC. 2) Atmosphere pressure in furnace appeared three peaks in the process of vacuum sintering, which corresponded with pyrolysis volatilization of forming agent, the reduction of metal oxides and the volatile of metal Mn in the stage of liquid phase sintering. Reducing the first and the second pressure peak was good to remove harmful gas as soon as possible, while appropriately raising the third time atmosphere pressure peak can avoid the matrix metal composition from volatile and be beneficial to obtain high quality sintered products. 3) Water toughening treatment increased the degree of supersaturation of alloy matrix and let the XRD diffraction peak of austenite to be width and dwarf. It also effectively promoted composition distribution uniformity of TiC particles and the binding phase around the phase interface, which was conducive to improve the comprehensive mechanical properties of alloy.The study of the impact abrasive wear performance comparison found that: 1) The abrasive wear resistance of coarse grained TiC-high manganese steel bonded carbides showed the tendency of decreasing firstly while increasing later with the gradual improvement of the impact load. The abrasive wear resistance under the high impact load was better than that under the low impact load. The wear-resisting property under the impact load of 2J/cm2 was worse and that under the impact load of 4J/cm2 was the best in the experimental range. 2) The impact abrasive wear resistance of coarse grain steel bonded carbide had obvious advantages compared with the average grain size of TiC-high manganese steel bonded carbides. Wear-resisting performance was increased by 80%, especially under the high impact load, so was the performance improved by 50% compared with ordinary grain steel bonded carbide by low pressure sintering. 3) The impact abrasive wear types of coarse grained steel bonded carbide includes chisel cutting abrasive wear, grinding abrasive wear, scratches type abrasive wear, and at the same time it also has a certain degree of fatigue wear. The proportion of the four wear types were different under different impact load.