Preparation Of TiC Reinforced Ni Based Composite Coatings And Study Of Organization And Properties

In this paper,mainly TiC and Ni60 powders were used as raw materials to prepare titanium carbide reinforced nickel-based composite coatings on carbon steel substrates by using plasma melting and laser melting equipment.The composition and microstructure of the physical phases within the coating were analysed using scanning electron microscopy with additional energy spectroscopy and X-ray diffractometry,and tested the microhardness,wear resistance and corrosion resistance of the coating.The effects of different power,scanning speed and titanium carbide content on the tissue properties of the prepared composite coatings and the distribution state,grain size and morphology of the titanium carbide in the coatings were investigated.The tissue evolution and wear resistance mechanisms during the preparation of titanium carbide reinforced nickel-based composite coatings were analysed and studied.The following main conclusions were drawn from specific studies.(1)The prepared TiC/Ni composite coating forms a fusion line at the junction of the coating and the substrate,and a high quality metallurgical bond is formed between the coating and the substrate.(2)There are more defects such as pores and cracks in the composite coating prepared by plasma cladding,and the defects in the coating increase significantly with the increase of scanning speed,while no obvious defects are observed in the laser cladding composite coating.However,the thickness of the coating increases with the increase of the melting power and the slowing down of the scanning speed,while the grain size changes in the opposite direction.(3)In the plasma cladding process: the enhanced phase TiC is mainly concentrated at the top of the coating and decreases from the outside to the inside,and there is a more obvious aggregation of TiC in the composite coating and more defects such as holes and cracks appear at the aggregation.In the laser cladding process: the enhanced phase TiC is distributed throughout the coating and is more evenly distributed,but the size of the titanium carbide grains grows significantly as the scanning speed decreases,the melting power increases and the titanium carbide content increases.(4)The microhardness in the composite coatings prepared by plasma cladding fluctuates considerably with the depth of the coating.The microhardness of the plasma cladding composite coating is highest at the highest scanning speed and increases and then decreases with increasing cladding power.The microhardness in the composite coatings prepared by plasma cladding fluctuates considerably with the depth of the coating.The microhardness of the plasma cladding composite coating is highest at the highest scanning speed and increases and then decreases with increasing cladding power.The TiC content has a greater influence on the composite coatings prepared by both the laser cladding and plasma cladding preparation processes,which both reach the maximum average hardness of the coating at the highest TiC addition(5)The average friction coefficient of the plasma clad composite coating decreases as the scanning speed decreases,rising and then decreasing as the cladding power increases.For laser cladding,the average coefficient of friction of the composite coatings at different scanning speeds is not very different and remains at around 0.48.The friction coefficient of the laser cladding composite coating with10% TiC is more stable,while the friction coefficient of the coating decreases with increasing titanium carbide content during the plasma cladding process.The wear mechanisms of the composite coatings are abrasive wear and adhesive wear,where abrasive wear is partly caused by shedding and breaking of TiC in the coating.(6)The composite coating prepared by plasma cladding has a pistil-like chromium carbide,which is strongly reinforced in the coating matrix by the branching crystals of the carbide,effectively enhancing the frictional wear performance of the coating.At the same time,the average friction coefficient is higher because the heat input has a greater influence on the thickness of the laser cladding composite coating(e.g.lower coating thickness at low power,high scanning speed and high titanium carbide content)and tends to wear into the substrate during the long wear process.(7)The corrosion resistance of the composite coatings prepared by plasma cladding decreases with the increase in scanning speed and cladding power and then increases.The corrosion resistance of the composite coatings prepared by laser cladding gradually decreases with the increase of scanning speed,and decreases with the increase of cladding power and then increases.The results of the polarisation tests show that the corrosion resistance of the composite coating decreases with increasing TiC content in laser cladding and then increases,while the corrosion resistance of the plasma prepared composite coating decreases with increasing titanium carbide content.