Study On Laser Melting Process And Properties Of Mo And Mo-5Co Alloys

In recent years,with the rapid development of domestic and international defense industry,aerospace and nuclear industry,Traditional high temperature resistant materials can't satisfy the application of high temperature structural materials,so it is necessary to find new high temperature heat resistant materials with excellent room temperature toughness,high temperature strength,high temperature wear resistance and high recrystallization temperature.Compared with the traditional hot-pressed and sintered molybdenum alloy,the pure Mo and Mo-5Co alloys prepared by Selective Laser Melting(SLM)have better toughness and high temperature wear resistance at room temperature,and good high temperature oxidation resistance.In this paper,we first explore the forming parameters of pure Mo in Selective Laser Melting.The single variable research method is used to explore the effect of laser power,scanning speed and scanning pitch on the density of pure Mo.In this paper,we first explore the forming process parameters of pure Mo in Selective Laser Melting.The single variable research method is used to explore the effect of laser power,scanning speed and scanning pitch on the density of pure Mo.To find the excellent parameters with relatively high density for the preparation of pure Mo and Mo-5Co alloy samples,and to produce pure Mo and Mo-5Co alloys with a density of over 97%.The optical fiber microscope,scanning electron microscope,electronic universal stretching machine,high temperature friction and wear testing machine,high temperature oxidation furnace and other test equipment are used to test and characterize the relevant performance.The optimization results of Selective Laser Melting in pure Mo show that the density of laser melting in pure Mo is affected by the process parameters such as laser power,scanning speed and scanning pitch.The effect of laser power is the biggest,and the scanning speed affects the next.The laser power exploration range is 175w~350w,the scanning speed exploration range is 200mm/s~1000mm/s,and the scanning pitch is 40?m,50?m,60?m.When the laser power P=300W,the scanning speed v=400mm/s,and the scanning pitch d=60?m,the pure Mo molded parts have higher density.The Mo-5Co alloy with 5wt% Co element was prepared by selective laser melting and forming process parameters.The SLM molding pure Mo and Mo-5Co alloys were tested with the hot-pressed pure Mo.The differences in hardness,compression properties,high temperature friction at room temperature and high temperature oxidation performance of SLM-formed pure Mo and Mo-5Co alloys were compared and analyzed,and the reasons for the difference in performance were analyzed.The results show that the hardness and room temperature compressive strength of SLM-formed pure Mo are higher than that of hot-pressed pure Mo.The hardness and compressive strength of SLM-formed Mo-5Co alloy is better than that of SLM-formed pure Mo.SLM molding is performed in the friction and wear test at 400 °C.Mo-5Co has high wear resistance and a friction coefficient of 0.1.The results of high temperature oxidation test show that the oxidation resistance of Mo-5Co alloy at 700 °C is higher than that of pure Mo.