| The coal industry occupies an extremely important strategic position in national economy. In recent period, the energy structure that the coal is the main energy source in our country will not be changed radically. Shearer picks that are installed in the most front of the machine are used to cut coal seam Improving the reliability of coal winning machine cutting picks and prolonging its service life will have a profound influence to the whole coal mining industry. Plasma cladding technology has a series of advantages such as high production efficiency, convenient operation, low equipment cost and so on. TiC has high hardness, high melting point, low density and excellent wear resistance, TiC is also used as a hard phase to strengthen the matrix in composite materials. Ni has good wettability with TiC, and Ni has good liquidity, high heat resistance, strong corrosion resistance and well toughness.In this paper, wear and impact resistant composite coatings with TiC as reinforcing phase, solid solution of y-Ni as matrix phase were in situ labricated on Q235low carbon steel substrate by plasma cladding technology with19Ni-37C-44Ti (at.%),30Ni-32C-38Ti (at.%),40Ni-26.5C-33.5Ti (at.%) and50Ni-22C-28Ti (at.%) mixed alloy powder as raw material respectively.Heat treatment process for pick was simulated to various coatings using BFX-12B type box electric furnace. The micro structure and phases composition of the coatings were identified by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the coating A with19Ni-37C-44Ti (at.%) mixed alloy powder as raw material was mainly composed of metal ceramic phase TiC and γ-(Fe, Ni) solid solution, there were also a few unreacted graphite particles. The coating B with30Ni-32C-38Ti (at.%) mixed alloy powder as raw material, the coating C with40Ni-26.5C-33.5Ti (at.%) mixed alloy powder as raw material and coating D with50Ni-22C-28Ti (at.%) mixed alloy powder as raw material were predominantly composed of metal ceramic phase TiC, γ-(Ni,Fe) solid solution and also some unreacted graphite particles, but the content and morphology of each phase composition were not identical. It presented a good metallurgical combination between coating and substrate, microstructure of the coatings were small dispersion and dense, with typical rapid condensation characteristics, dark grey TiC primary phase with high hardness was evenly distributed in the y-Ni solid solution based phase with good strong toughness.Micro hardness profiles along the depth direction of the coatings were measured by a Vickers hardness tester. Results show that the coatings all have higher hardness distribution than35CrMnSi, with the increase of Ni content in the coatings, the mircohardness values decrease; Within the same coating, the mircrohardness reduced from the coating surface to combination area.The dry sliding friction and wear properties in room temperature of various coatings were tested through the pin on disc wear testing machine, and the results show that under the condition of room temperature dry sliding friction and wear test, the coatings have less wear weightlessness and low friction coefficient than35CrMnSi. And wear weightlessness of these coatings are not sensitive to the load. With the increase of Ni content in the coatings, the abrasion resistance decrease, but considering about the existence of micro-cracks in the coating A and the operation condition of the coal winning machine, the coating B with30Ni-32C-38Ti (at.%) mixed alloy powder as raw material is the best choice. |
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