Effect of volume fraction of (Cr, Fe)7C3 carbides on corrosion resistance of the Fe-Cr-C hardfacing alloys at Cr/C=6

In this investigation, three different chemical compositions of Fe-Cr-C alloys were fabricated on AISI 1010 steel substrates by gas tungsten arc welding (GTAW). The optical emission spectroscopy (OES), optical microscopy (OM), scanning electron microscopy (SEM), techniques and corrosion test were used for determining chemical composition studying the microstructure and corrosion behavior of the Fe-Cr-C alloys. The OM and SEM results show that the microstructure of these alloys consisted of (Cr,Fe)7C3 carbides with austenite, and by increasing of the carbon and chromium content in hardfacing alloys, the volume fraction of (Cr,Fe)7C3 carbides in microstructure was increased. The polarization curves of the corrosion tests show that the increase of the volume fraction of (Cr,Fe)7C3 carbides in the microstructure promotes the corrosion resistance of the Fe-Cr-C hardfacing alloys. The corrosion mechanism of the Fe-Cr-C hardfacing alloys was intergranular and galvanic corrosion

Microstructure and mechanical properties of friction stir welded ferrite-martensite DP700 steel

In the present work, friction stir welding technique was applied on 2 mm thick ferrite-martensite DP700 steel sheets at rotational speeds of 600, 800 and 1000 rpm. The microstructure and mechanical properties of the welds were evaluated. It was found that Zener-Hollomon parameter decreased with increasing rotational speed that leads to grain coarsening in the stir zone. It was also found that increment of rotational speed increased softening phenomenon in sub-critical heat affected zone. The results also showed that the presence of WC particles in the stir zone, which was due to the tool wear, as well as formation of a soft ferrite band degrade the tensile properties at rotational speed of 600 rpm while HAZ softening was responsible for reduction of strength and ductility in conditions of 800 and 1000 rpm

Effect of Austenitizing Temperature on Mechanical Properties of the Mixed Bainite - Martensite Microstructure in CrMoV Steel

<div><p>The effect of austenitizing temperature on mechanical properties of the mixed bainite - martensite microstructure in CrMoV steel was studied in the present work. The result showed that at low austenitizing temperature (910°C - 1000°C), the mixed microstructures containing 12-28% volume fraction of lower bainite showed higher yield and tensile strength than fully martensitic microstructure. The partitioning of the prior austenite grain by lower bainite was found to cause a refinement of the martensite packet size. In addition the strength of the lower bainite in the mixed microstructure is enhanced by plastic constraint induced by the surrounding stronger martensite. By increasing the austenitizing temperature from 1000°C to 1200°C (40min), the YS, UTS, %EL, %RA and CVN impact energy decreased for all samples. This is attributed mainly to the increase in austenite grain size and width of bainite sheaves.</p></div