Influence Of Cooling Conditions And Magnetic Field On Microstructure And Properties Of Shearer Sliding Boots Surfacing Layer

Sliding shoes are a key bearing component on the base of coal shearers. Due to the poor working environment and the increasing weight of the coal shearer, the minimum requirement for the various properties of sliding shoes is increased. The materials of sliding shoes must possess a good strength, wear resistance and toughness. Consequently, the proper materials and technologies should be chosen to ensure that the sliding shoes can meet the requirement of strength under the real working conditions, and simultaneously, hold a high wear-resistant property under the severe wear. The method is the key way to promote the serving effect of coal shears. Combined with the actual production of coal shear manufactures at home and abroad, the processing techniques of the wear-resistant layers of coal shears, especially high-power coal shears, still mainly use surfacing welding on the guide face. The choice of the reasonable matrix, wear-resistant materials and processing techniques to improve the working reliability is still one of the important and difficult points in the researches of domestic related enterprises at the current stage.The paper was aimed at the problems concerned of the wear failure of sliding shoes. Wear-resistant layer was welded on the surface of sliding shoes under the cooling condition and the magnetic field. Furthermore, the microstructure, hardness, residual stress and wear property of the surfacing layers were analyzed to study the influence of the cooling condition and the magnetic field on the structure and properties of the surfacing layers. Eventually, a theoretic basis is provided for the actual application.Under the alkaline, brine and water-cooling conditions, the trend of columnar crystals changing into equiaxed crystals increased in the structure of the surfacing layers, moreover, the amount of precipitated carbide particles in the matrix of martensite increased in turn. The hardness of the surfacing layers were improved than that under the air-cooling condition, furthermore, the improved range of the hardness under the water-cooling condition was higher than those under other cooling conditions. In addition, the wear loss of the surfacing layers under the water-cooling condition markedly declined compared with the air-cooling condition, moreover, the decreased range of the wear loss gradually increased with load. However, the surfacing layers possessed a high residual stress under the water-cooling condition, which could contribute to welding cracks and some similar defects.After magnetic field was operated under the rapid cooling condition, the microstructure of the surfacing layers was mainly dominated by equal axial grains, furthermore, the size of grains was finest under the transverse magnetic field. The hardness of the surfacing layers under three kinds of magnetic field was lower than that without a magnetic field. Moreover, the hardness increases first and then decreased with the increasing intensity of the magnetic field. The transverse magnetic field could obviously improve the hardness under a low-intensity magnetic field; the longitudinal magnetic field owned a similar effect on the hardness under a high-intensity magnetic field; in addition, the oblique magnetic field could provide a high hardness under the low- and high-intensity magnetic field. As the intensity of the magnetic field was 0.06 T, the transverse magnetic and the oblique magnetic field had a higher ability to promote the hardness of the surfacing layers than the longitudinal magnetic field. Moreover, after the application of external magnetic field, the residual stress in the interface of the surfacing layers decreased obviously; the phenomena could increase the serving life of the surfacing layers.The friction coefficient of three kinds of the magnetic field shared a similar variety law. The wear loss presented a V-shaped variation tendency with the increasing intensity of the magnetic field. When the low load reached 200 N, the surfacing layers possessed a best wear-resistant property and a smallest wear loss 81.1mg under the longitudinal magnetic field. When the load was medium and high, the surfacing layers performed an excellent wear resistance and the wear loss reaches 216.2mg with the 600 N load under the oblique magnetic field. Under the optimized intensity of the magnetic field, the wear mechanism was abrasive wear and the wear morphology was mainly dominated by tiny furrows, furthermore, the surfacing layers showed a strong resistance to adhesion wear and abrasive wear.