Carbide Precipitation In Steel Research Articles

Effect of different thermal treatment temperatures on dimensional stability and mechanical properties of M50 steel

By using field-emission scanning electron microscopy, X-ray diffraction, impact and tensile-property tests, the effect of thermal treatment temperatures in stabilization treatment on the microstructure, dimensional stability and mechanical properties of M50 bearing steel was studied. Results show that the size of M50 steel decreases due to carbide precipitation at 400 °C, 420 °C, 440 °C and 480 °C, and increases due to martensite transformation at 460 °C. In the thermal treatment temperature range of 400–480 °C, the amount of secondary carbide precipitation in M50 steel increases first and then decreases with the increase of thermal treatment temperature, and the amount of carbide precipitation in the steel reaches the maximum at 460 °C. During the thermal treatment temperature range of 400–460 °C, the residual austenite gradually decomposes and decreases in quantity. However, at 480 °C, the residual austenite has relatively higher carbon content to make it more stable and less likely to decompose. At the same time, the tensile properties are slightly improved, the impact toughness decreases at 460 °C and improved under other conditions.

Heterogeneous nucleation effect of in situ nanoparticles on the metal–matrix microstructure

Transmission electron microscopy (TEM) and atom probe tomography (APT) were combined to comprehensively characterize the change of microstructure under the heterogeneous nucleation effect of in situ nanoparticles. Results indicate that these in situ nanoparticles have a positive effect on optimizing structure and inducing carbide precipitation in steel. This work sheds light on a potential pathway for the improvement of the microstructure of steel by investigating the heterogeneous nucleation effect of in situ precipitation nanoparticles.

Modeling of Niobium Carbide Precipitation in Steel

Modeling of Niobium Carbide Precipitation in Steel

Advances in Physical Metallurgy and Processing of Steels. Microstructural Evolutions with Precipitation of Carbides in Steels.

The studies on the crystallographic features of diffusional transformation of austenite in various steels have been reviewed. A primary ferrite forming at an austenite grain boundary is related to at least one of the austenite grains separated by the boundary with the Bain correspondence. In the case of the microstructures containing both ferrite and carbides such as pearlite, degenerate pearlite, interphase precipitation of alloy carbides, and upper and lower bainites, the crystallographic relationships between ferrite and carbides provide further information to elucidate the transformation mechanisms. In the present report, therefore, the orientation relationships between ferrite, carbide and austenite as well as the habit planes of platelike transformation products and the mechanisms of transformations are discussed.

Super-carburization of low alloy steel and low carbon steel by fluidized-bed furnaces

The present work is concerned with super-carburization treatment on low alloy steel AISI 4135 and plain carbon steel AISI 1020 by fluidized-bed furnaces. Super-carburization is a repetition of carburization and precipitation heat treatment processes to produce a dense spheroidized carbide layer near to the steel surface. Carburization was conducted at 930°C and 800°C in an endothermic atmosphere with a carbon potential higher than 1.3% generated by the direct boosting of propane and air into the bed. The precipitation of carbides in steels was conducted at 600°C in a nitrogen-fluidized bed. The rapid cooling rate associated with the great undercooling of the fluidized bed effectively suppressed the formation of network cementite when carburized steels were cooled from the austenitizing temperature to the precipitation temperature. This phenomenon has made it possible for even a plain carbon steel to be super-carburized without difficulty.

Effects of plastic deformation on carbide precipitation in steel

The influence of plastic deformation on carbide precipitation in carbon steels containing 0.47, 0.74, and 0.88% carbon has been studied, using electron microscopy and magnetic analysis. Cold-work restrains precipitation in quenched steels: in a sufficiently deformed medium-carbon martensite normal precipitation of the ϵ-carbide in the first stage of tempering can be suppressed and, on heating above 200°C, the precipitation of cementite is hindered. If a steel is first tempered to precipitate an iron carbide and then deformed, the precipitate will tend to redissolve in the cold-worked matrix. Metallographic evidence of such a partial re-solution of an ϵ-carbide precipitate has been obtained in a steel tempered to the end of the first stage before deformation and subsequently aged at 130°C. Possible evidence of a similar, but appreciably smaller, solution effect was found in steels containing fine particles of cementite. It is suggested that these effects are a consequence of the strong interaction between carbon atoms and lattice defects in iron.