Abstract
In this study, the effects of adding Ni in different ratios to Fe-matrix material containing C-Nb-V produced by powder metallurgy on microstructure, tensile strength, hardness and corrosion behaviors were investigated. Fe-C and Fe-C-Nb-V powders containing 5%, 10%, 13%, 15%, 20%, 30% and 40% nickel were pressed at 700 MPa and then sintered in an Ar atmosphere at 1400 °C. Microstructures of the samples were characterized with optical microscope, scanning electron microscope (SEM) and XRD. Corrosion behaviors were investigated by obtaining Tafel curves in an aqueous solution containing 3.5% NaCl. Mechanical properties were determined by hardness and tensile testing. While Fe-C alloy and Fe-C-Nb-V microalloyed steel without Ni typically have a ferrite-pearlite microstructure, the austenite phase has been observed in the microstructures of the alloys with 10% nickel and further. Yield and tensile strength increased with nickel content and reached the highest strength values with 13% Ni content. The addition of more nickel led to decrease the strength. Analysis of Tafel curves showed that corrosion resistance of alloys increased with increasing nickel concentration.
Highlights
Microalloyed steels are known as steels containing elements such as titanium, vanadium and aluminum at a maximum of 0.20% by wt
This may be the result of the creation of small precipitates such as niobium carbonitride (NbCN)
The EDS analysis indicated that Nb and V formed into grains and grain boundaries in the solution as precipitates (Figure 3a,b)
Summary
Microalloyed steels are known as steels containing elements such as titanium, vanadium and aluminum at a maximum of 0.20% by wt. These steels are a group of materials with superior properties such as excellent durability, weldability, corrosion resistance and toughness achieved by applying different strength enhancer mechanisms and appropriate thermomechanical procedures [1,2]. Powder metallurgy (PM) is defined as a method of producing small, functional, incompatible, difficult-to-manufacture parts such as composite structures, with high strength and minimum tolerance, in a more advantageous and economical way compared to other production methods. Nickel improves the resistance against the corrosion and oxidation at elevated temperatures
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