Browsing by Author "Hayat F."

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Investigation of corrosion behaviour of boronised cold rolled high manganese steel
(2023-01-01) Sezgin C.T.; Hayat F.
Corrosion behaviour of boronised high manganese steels (HMS) was investigated in this study. Pack-boronising was processed at 950°C, 900°C and 850°C for 2 h, 4 h, and 6 h. Boride layers of HMS unpredictably exhibited saw-tooth morphology. FeB, Fe2B, MnB and SiC phases were determined by XRD analyses. The increase in boronising temperature and time caused an increase in boride layer thickness. Although the corrosion rates were lower in boriding processes at 850°C, the corrosion rate of most of the samples boronised at 900 and 950°C was higher than the un-boronised HMS due to micro-cracks and pores formed in the boride layers.
The effects of boriding process on tribological properties and corrosive behavior of a novel high manganese steel
(2022-02-01) Sezgin C.T.; Hayat F.
In this study, wear and corrosion behavior of a novel borided high manganese steel (HMS) produced by the researchers was investigated. After the sheets were cold-rolled, they were annealed. HMS was borided at 850, 900, and 950 °C for 2, 4, and 6 h through the pack-boriding process. Borided HMS uncommonly exhibited a saw-tooth morphology like low alloy steels due to similar crystal structures of MnB and FeB. XRD analysis showed the existence of SiC, FeB, MnB and Fe2B phases. The present study indicated a silicon-rich zone by EDX mapping. The formation mechanism of silicon-rich zones was explained and expressed with the term “compact transfer of silicones”. The boriding time and temperature increased the thickness of the boride layer from 26.13 μm to 109.04 μm. The highest hardness value was observed in sample 5 (1757 HV0.05). The activation energy of borided HMS was quite low compared to several high alloy steels in the literature. Daimler-Benz Rockwell-C adhesion test showed that adhesions of borided HMS surfaces were sufficient. The “egg-shell effect” that emerge due to the high silicon rate did not occur. In the wear tests applied under 5, 10, and 15 N loads, the borided HMSs exhibited a better wear resistance compared to the base metal (BM). However, the wear test was applied under 5 N load and BM had a better performance than several borided HMSs because of the phase transformations. In general, the borided samples had lower corrosion rates compared to the unborided ones.
The microstructure and mechanical behavior of trip 800 and dp 1000 steels welded by electron beam welding method
(2020-01-01) Sezgin C.T.; Hayat F.
TRIP 800 steel and DP 1000 steel welded by using the electron beam welding (EBW) method were investigated in this study. Martensite was a dominant phase at the fusion zone (FZ) of both steels. In addition, bainite and austenite were observed in the FZ of TRIP 800. The hardness of FZ and heat affected zone (HAZ) of both steels were higher than their base metals. The hardness of FZ of the TRIP 800 joinings was higher than the FZ of DP 1000. Ductility and tensile strength decreased at both of the joinings. However, this decrease became higher at the DP 1000 steel joinings compared to the TRIP 800 joinings. It was observed that the TRIP 800 joining absorbed more energy than the DP 1000 joining at impact notch test for each temperature.
Wear behavior of borided cold-rolled high manganese steel
(2021-10-01) Hayat F.; Sezgin C.T.
In this study, a novel high-manganese steel (HMS) was borided at 850, 900 and 950 °C for 2, 4, and 6 h by the pack boriding process. Contrary to previous literature, borided HMS uncommonly exhibited saw-tooth morphology like low alloy steels, and manganese enhanced the boron diffusion. Another striking analysis is that the “egg-shell effect” did not occur. The present study demonstrated the silicon-rich zone for the first time in the literature by EDX mapping. Moreover, the formation mechanism of silicon-rich zones was explained and termed as “compact transfer of silicones (CTS)”. XRD analysis showed the existence of FeB, Fe2B, MnB and SiC phases. The boriding time and temperature increased the thickness of the boride layer from 31.41 μm to 117.65 μm. The hardness of the borided layer ranged from 1120 to 1915 HV0.05. The activation energy of borided HMS was found to be a very low result compared to high alloy steel investigated in the literature. The Daimler-Benz Rockwell-C adhesion test showed that adhesions of borided HMS surfaces are sufficient. The dry sliding wear tests showed that boriding treatment increased the wear resistance of untreated HMS by 5 times. The present study revealed that the boriding process extended the service life of HMS components.