چكيده به لاتين
In this study, the microstructure, hardness, and dry sliding wear behavior of the hardfaced layers made by cored wires Fe-B, Fe-B-C and Fe-B-C-Ti alloy were investigated and the titanium effect was studied by comparing and analyzing the microstructure and wear properties of the three hardfacing alloys. ST37 steel was used as the substrate and the deposition of the hardfaced layers was conducted by the flux cored arc welding (FCAW) process under single-, two-, and three-pass conditions. Dry sliding wear tests were performed by a pin-on-disk apparatus, based on ASTM-G99, at room temperature (25 C) at the normal applied loads of 50, 100, and 150 N with a constant speed of 0.08 m/s for a sliding distance of 1000 m. The microstructural and phase analyses were carried out by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), respectively. In samples hardfaced with Fe-B cored wire, with an increase in boron content of 3.18wt.% the microstructure consists of a lamellar eutectic (α-Fe2B) and primary particles of Fe2B and some FeB around the Fe2B columnar particles, while in samples hardfaced with Fe-B-C cored wire, with an increase in boron content of 3.12wt.% and an increase in carbon to 0.38wt.%, the microstructure includes eutectic (P-Fe2B), which is a Fe2B phase in the skeletal (fishbone-like) and eutectic (P-Fe3(C,B)), which is the Fe3 (C, B) rays are daisy-like, as well as some FeB around the primary Fe2B columnar particles. The presence of cracks on the surface of the basic Fe2B column blades due to the formation of FeB and the difference in the Fe2B thermal expansion coefficient and FeB was observed in samples hardfaced with Fe-B and Fe-B-C cored wires. So, the results showed that the hardfaced layer produced by the single-pass process contains TiC rectangular phase distributed within a matrix containing ferrite and the eutectic of (α-Fe2B). But, the hardfaced layers produced by the two- and three-pass process contain TiB2 hexagonal phase in addition to TiC, which prevents the formation of detrimental FeB phase around Fe2B and reduces the number of micro-cracks. Moreover, the sample hardfaced by the three-pass process had the best wear resistance due to the greater hardness resulted from the higher amounts of TiC and TiB2 phases. In addition, increasing the number of passes has led to the reduction of wear rate at all the three applied loads. At the applied load of 100 N, the wear mechanism for the all three hardfaced samples was an oxidation wear. However, at the applied load of 150 N, the wear mechanism was a combination of oxidation and brittle fracture.
