Abstract
High chromium steel has been synthesized by an induction furnace adopting electromagnetic stirring (EMS). Varying amounts of cobalt was added to obtain 3, 6, and 12% Co in the steel. The melt was allowed to solidify with or without EMS in a rotary magnetic field. The effects of the varying cobalt content and the stirring have been characterized by the microstructural evolution and the consequent improvement in mechanical properties. The application of a rotary EMS during solidification has shown a significant effect on the grain refining, the reduction of element segregation, the promotion of eutectic volume fraction, and the consequent improvement of mechanical properties, including hardness and high-temperature strength. The formation mechanism of the eutectic structure and the precipitation of M7C3 and M23C6 carbides was discussed according to the calculated phase diagram. The increment of cobalt content improved the eutectic volume fraction. Cobalt addition also enhanced the hardness and the yield tensile strength, provided that the ingot structure was homogenized by the EMS.
Highlights
High chromium steel is characterized by a good mechanical performance at an elevated temperature, which is generally used in a variety of engineering applications, such as the manufacturing of components for advanced power plants
The macrostructures and microstructures of the samples were observed by optical microscopy and the scanning electron microscopy (SEM) respectively
Compared with the structure observed in an as-cast steel, the grains became finer when the electronmagnetic stirring (EMS) was imposed
Summary
High chromium steel is characterized by a good mechanical performance at an elevated temperature, which is generally used in a variety of engineering applications, such as the manufacturing of components for advanced power plants. In the solidification of metals and alloys, forced stirring can be used to improve the microstructure and performance of the ingots. EMS has been reported to promote equiaxed grain the to promote equiaxed reduce the average grain size in alloys such as copper variousalloys steels [14,15],. Solidification of metals led to the refinement and better distribution of precipitates [28,29] In this this work, work, the the effect effect of ofcobalt cobaltaddition addition was was studied studied in in detail detail using using three three kinds kinds of of steels, steels, with with each each of of their their as-cast as-cast ingots ingots being being compared compared in in terms terms of of microstructure microstructure and and mechanical mechanical properties. Size, eutectic structure, and the change in hardness andtemperature high temperature strength was discussed
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