Development Of Age Hardening Wear Resistance Electrode For Hardfacing

An electrode of age hardening wear resistance for hardfacing is studied in the paper. The electrode with low hardness in as-welded and good machinability is possessed of high hardness and good wear resistance by aging in high temperature while the materials that can be found in the marketplace are always possessed of high hardness with poor machinability or low hardness, good mchinability with poor wear resistance. The electrode designed by the author unites wear resistance and machinability to satisfy the demands of production today. One low-hydrogen type basic coating slag system that is CaCO3-CaF2-TiO2-ZrO2-SiO2 is chosen with a lot of experiments. A simple and convenient method for crack testing is introduced and the cracking resistance of hardfacing alloy can be evaluated qualitifiedly with it. The influence of microstructure on the machinability is analyzed concisely. The deposited metal microstructure in as-welded is compared with that after aging through optical microscope, scanning electron microscope and X-ray diffraction analyses. The mechanism of age hardening is investigated primarily, Namely welding is such a course that the workpieces are heated and cooled unevenly, most of alloying elements have been in the matrix in the form of solid solutions. It makes the temperature of martensite starting transformation MS so low that a lot of austenite can be retained in room temperature. That makes the values of hardness about 30HRC so low that it can be machined easily. After stress relief aging in high temperature, the austenitic matrix with little carbon content resulted from the complete precipitation of carbide would transform into martensitic matrix that heightens the hardness and wear resistance. The function of elements in hardfacing alloy including C, Cr, Mn, Ti, W, Mo, V, B, RE, Cu and the effect of thesealloying elements on the hardness and microstructure are also analyzed. Finally the abrasive resistance, thermal fatigue resistance and oxidation resistance in high temperature are presented through experiments.