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.

In this study, Mo-Si-B based coatings were produced using tungsten inert gas (TIG) process on the medium carbon steel because the physical, chemical, and mechanical properties of these alloys are particularly favourable for high-temperature structural applications. It is aimed to investigate of microstructure and microhardness properties of Mo-Si-B based coatings. Optical microscopy (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the microstructures of Mo-Si-B based coatings. The XRD results showed that microstructure of Mo–Si–B coating consists of α-Mo, α-Fe, Mo2B, Mo3Si and Mo5SiB2 phases. It was reported that the grains in the microstructure were finer with increasing amounts of boron which caused to occur phase precipitations in the grain boundary. Besides, the average microhardness of coatings changed between 735 HV0.3 and 1140 HV0.3 depending on boron content.

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.

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