Posted 28 Dec 2010 18:59
The use of a wide range of cast iron, in the developed countries, iron and steel ratio of about 0.47 to 0.5, in some sectors even more than the use of cast iron steel. Cast iron material in the production of a large proportion of low cost, can be cast, pressure processing, cutting, heat treatment can make it through the mechanical properties of a wide range. But its corrosion resistance, mechanical properties and can not fully meet the performance. Although the surface treatment of cast iron are many, but more or less the existence of some limitations, and none can solve the engineering adaptation, with performance that is the premise of ensuring the process and economy. Welding technology can achieve surface alloying metal to make steel with wear and corrosion properties of surface materials has been widely used in the manufacture of parts and repair the surface. Currently available from the fluxing layer in many ways, such as the oxyacetylene flame powder spray, plasma arc spray, high frequency induction melting and laser remelting. Oxyacetylene flame spray technology is a more mature corrosion surface treatment technology, with its energy-saving, low cost, efficient, flexible and reliable access to the advantages of the coating is widely used in surface treatment of a variety of materials. Fe-based self-fluxing alloy powder and nickel-based self-fluxing alloy powder is the most common spray materials, the same time, nickel-based self-fluxing alloy is a widely used with excellent corrosion resistance of the coating material. Spray the surface of cast iron sprayed layer and the substrate Ni65A binding site organization is divided into: spray zone, the interface area (transition layer), heat affected zone, base metal matrix. Spray layer of nickel solid solution matrix with hard particles dispersed phase; with the surface, each element diffusion, the formation of bright white ribbon of the transition layer, base metal matrix, less heated, organizational change, and still is a child care's body + carbide organization. Carbon diffusion into the spray layer, and Cr to form (Fe, Ni) 23C6 and Cr carbide, which hinder the spray coating of hard phase grain growth, resulting in grain refinement, formation of significant trees cast iron dendrites. High temperature diffusion, the interface zone appears 2Ni solid solution, the composition of coating and the substrate by the combination of diffusion at the interface of the substrate surface temperature, when the substrate surface temperature is high enough, the matrix elements of the diffusion coating to the amount of Fe larger diffusion distance is longer, at the interface can form dense full 2Ni solid solution of the white layer.