Effect Of Tungsten On Properties Of Superaustenitic Stainless Steel And Its Mechanism

00Cr24Ni22Mo7N is the so-called one of the main brand of superaustenitic stainless steel containing 7%molybdenum,The solid solution state of steel has excellent plastic,toughness and strength,Its performance is higher than common austenitic stainless steel and superaustenitic stainless steel containing 6%molybdenum.The corrosion resistant performance and mechanical performance even more than some nickel base corrosion resistant alloy,However,If the molybdenum content is too high,the deformation resistance of steel increases,thermoplastic reduces and easy to form intermetallic phase in steel at the same time,it will affect the performance of the steel,greatly restricted the development of super austenitic stainless steel.This paper uses 2%tungsten instead of 1%molybdenum,the precipiated phase of the two superaustenitic stainless steels have been studied by employing metallographic,scanning electron microscope and transmission electron microscope.Moreover,observe and study the corrosion resistance and impact resistance of the two kinds of alloys,thoroughly analyzed the influence mechanism of tungsten in the superaustenitic stainless steel.The results show that the two kinds of alloy completely solid solution at 1200?,the temperature of the solid solution system for 60 min.In the aging temperature range 750?1000?,the main precipiated phase is sigma(a)phase,with the increase of temperature,precipitation of sigma phase process is Chain along grain boundary precipitation,precipitate along three level at the junction,and accompanied by a small amount of intracrystalline granular precipitation(?)Gradually to the transgranular growth,rendering layer is full of the whole grain boundary precipitation(?)Grain boundary distribution is discontinuous,The a phase back into the matrix?In the temperature range 750?1000? under the condition of heat preservation for 60 min,precipitation accelerated first along with the rise of temperature,reach the maximum at 950?,then with the temperature increase,precipitation reduced speed.In the temperature range 750?1000? under the condition of heat preservation for 60 min,using 2%tungsten instead of 1%molybdenum can delay the grow up of sigma phase.Through found corrosion test in the solution,adding tungsten elements can improve the pitting corrosion resistance of the alloy during short time aging treatment.For superaustenitic stainless steel after aging,the poor chrome area near the grain boundary of sigma phase become the location of the pitting corrosion occurred more easily.Because of the tungsten element diffusion speed slower,lower than that of Cr and Mo element,can delay the grow up of sigma phase,thus improved the pitting corrosion resistance of alloy.