Sintered stainless steel has a wide range of applications mainly in the automotive
industry. Properties such as wear resistance, density and hardness can be improved by addition of
nanosized particles of refractory carbides. The present study compares the behavior of the sintering
and hardness of stainless steel samples reinforced with NbC or TaC (particles size less than 20 nm)
synthesized at UFRN. The main aim of this work was to identify the effect of the particle size and
dispersion of different refractory carbides in the hardness and sintered microstructure. The samples
were sintered in a vacuum furnace. The heating rate, sintering temperature and times were
20°C/min, 1290°C and 30, 60 min respectively. We have been able to produce compacts with a
relative density among 95.0%. The hardness values obtained were 140 HV for the reinforced
sample and 76 HV for the sample without reinforcement.
Mechanical properties of ferritic-marensitic steels can be improved through dispersion of fine particles with large industrial applications like nuclear, military and aeronautic areas. Steels used at nuclear reactors suffer some damage when exposure to various kinds of radiation such as gamma, plasma, neutrons among others. Special steels have been studied to resist these processes in which cause a significant degradation of these materials. Reduced activation ferritic/martensitic steels (RAFM) are used for fusion structural materials with the substitution of some alloying elements such as Mo, Nb and Ni present in the commercial martensitic steels by other elements which exhibit faster decay of induced radioactivity, such as Ta, W and V. This present work study the development of EUROFER97 steel reinforced with 3wt% of tantalum carbide (TaC).
Steel is an alloy EUROFER promising for use in nuclear reactors, or in applications where the material is subjected to temperatures up to 550°C due to their lower creep resistance under. One way to increase this property, so that the steel work at higher temperatures it is necessary to prevent sliding of its grain boundaries. Factors that influence this slip contours are the morphology of the grains, the angle and speed of the grain boundaries. This speed can be decreased in the presence of a dispersed phase in the material, provided it is fine and homogeneously distributed. In this context, this paper presents the development of a new material metal matrix composite (MMC) which has as starting materials as stainless steel EUROFER 97, and two different kinds of tantalum carbide-TaC, one with average crystallite sizes 13.78 nm synthesized in UFRN and another with 40.66 nm supplied by Aldrich. In order to improve the mechanical properties of metal matrix was added by powder metallurgy, nano-sized particles of the two types of TaC. This paper discusses the effect of dispersion of carbides in the microstructure of sintered parts. Pure steel powders with the addition of 3% TaC UFRN and 3% TaC commercial respectively were ground for 5 hours in the planetary mill. Each of the resultant particulate samples were cold compacted under a uniaxial pressure of 600MPa in a cylindrical die 5 mm in diameter. Subsequently, the compressed were sintered in a vacuum oven at a temperature of 1250°C with an increment of 20°C and 10°C per minute and maintained at these isotherms for 60 minutes. The distribution, size and dispersion of steel and composite particles were determined by X-ray diffraction, laser particle size and scanning electron microscopy(SEM). The structures of the sintered bodies were observed by optical microscopy(OM) and scanning electron microscopy(SEM).
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