Experimental Research On Solid Transformation Of GCr15and H13Steel

Transformation is a basic theory of Material science, which includes eutectoiddecomposition, bainite transformation, and martensite transformation and so on. In thispaper, influences of a series of heat treatments on transformation of GCr15and H13steel were studied, and transformation products of GCr15and H13were also observedand analyzed by Axiovert-25CA optical microscope(OM), QUANTA-400scanningelectron microscope(SEM), laser scanning confocal microscope(LSCM), and JEM-2100transmission electron microscope(TEM).The results are as below: furnace heating to800℃, and cooling slowly to700℃and keep the temperature for2hours and finallyget the samples out of the furnace after furnace cooling to500℃. The result of energyspectrum analysis show that aggregation growth of carbides coincide withGibbs-Thomson theorem that the smaller of radius of carbides particles, the bigger ofsolubility of them, and solute atoms are apt to diffuse from small particles to biggerones. the nucleation and growth of upper bainite are in the grain boundary of austenite,therefore, bainite structure is formed inside the austenite grains. The two-dimensionalshape of bainite carbides is sinewy, while the three-dimensional shape is laminar. Theshape of cryptocrystalline martensite of GCr15steel is the conformity organization oflath martensite and plate martensite, and the majority is the lath martensite. Thesubstructures of cryptocrystalline martensite are fault and high density dislocations,however, twin crystal do not find in the microstructure. the hardness after quenching isincreasing with the rising of solubility of carbon and alloying elements. when temperingat200~560℃, the microstructure will transform from tempered martensite to temperedsorbite, and secondary hardening appears at520℃.