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In order to understand the thermal corrosion of iron to diamond at high temperature, water atomized pure iron powder improves the bonding strength of the bonding agent to diamond and the self-sharpness of the tool. The development trend of iron-based bonding agents mainly has the following aspects:
(1) Cast iron binder. The cast iron binder has been successfully used in diamond grinding wheels for ceramics. Its main components are: grey cast iron cutting powder and carbonyl iron powder. Because the cast iron powder contains silicon, the sintering process makes the graphite spheroidized to improve the strength of the bonding agent. The graphite in the cast iron can prevent the welding during the grinding process, make the surface of the workpiece clean, and reduce the surface roughness. Cast iron powder is saturated with carbon, so that there are very few carbon atoms diffused by the diamond when sintered at high temperature, thereby suppressing the deterioration of the diamond; carbonyl iron powder can reduce the carbon content of the cast iron and the brittleness after sintering, improve the sinterability of the cast iron powder and the diamond Adhesion. Compared with the bronze-based grinding wheel, the cast-iron grinding wheel has the advantages of high strength, large grinding ratio, convenient control of the grinding speed, and low surface roughness of the workpiece. The cast iron binder has also been successfully applied to diamond circular saw blades for stone.
(2) Superfine iron powder. Ultrafine iron powder has high sintering activity, and the hot-pressing sintering temperature can be reduced to below 800 ° C, which can effectively avoid the erosion of diamond by iron. At the same time, the ultrafine iron powder matrix has high strength, high hardness, and diamond wear resistance it is good.
(3) Add alloying elements. 1) Add a quantitative amount of low melting point elements or alloys such as copper, zinc, tin, phosphorus, and iron eutectic alloys as the bonding phase, let it melt earlier in the sintering process and become a liquid phase, so that the binder has liquid phase sintering Characteristics to obtain the ideal dense sintered body. 2) Add a small amount of high hardness and high melting point framework components, such as tungsten, tungsten carbide, metal oxide, etc., to improve the hardness and wear resistance of the bonding agent. 3) Strengthening ingredients, such as adding an appropriate amount of nickel to solid-solution strengthen the iron matrix; adding a small amount of carbon and silicon elements to form Fe, C or Fe, Si strengthening iron-based matrix; adding a small amount of phosphorus can significantly improve iron The hardness and abrasion resistance of the substrate and slowing down the hot erosion of iron to diamond, and improving the self-sharpening effect are significant; adding a small amount of molybdenum, beryllium and rare earth elements can play the same role. 4) Add appropriate amount of affinity element to enhance the chemical affinity of iron-based binder to diamond. For example, adding 3% drill can greatly improve the holding power of iron-based binder to diamond; adding appropriate carbide-forming elements (Cr, Ti), so that it can generate stable carbides at high temperatures, strengthen the carcass, and improve grip.
(4) Pre-alloyed or partially pre-alloyed. Due to the short hot-pressing sintering time, especially when the temperature is low, the high-melting alloy elements have no time to diffuse alloying, and still exist in the form of simple substance, which cannot fully function. Iron-based binder pre-alloying or partial pre-alloying can effectively solve The problem. For example, Fe-Ni-Cu, Fe-Ni-Cu-Sn, Fe-Co-Cu and other pre-alloyed powders have been used in large quantities for drilling tools; 663 bronze, Cu-Sn20, Cu-P, Fe-P, Fe- B alloy powder to reduce sintering temperature; adding Fe-Cr, Fe-Mn alloy powder is more effective than adding Cr or Mn directly.