Evaluation of properties in steel with boride coatings under hydrogen

In this study present the benefit of boride coating on surface of ASTM A-36 steel and the evaluation of the properties of the hard coatings under hydrogen permeation. The ASTM A-36 steel was surface hardened by diffusion boron atoms at temperature at 950 °C for 3, 5, and 7 h using the dehydrated boron paste-pack method. The hard coatings obtained on surface A-36 steel were examined using scanning electron microscopy combined with energy dispersive spectrometry and X-ray diffraction. In addition, the hydrogen was introduce into samples with hard coating through cathodic charging applying a current density of 50 mA/cm2 by 0.5 M sulfuric acid solution kept at a room temperature. Three-point bending and instrument nanoindentation were evaluated on sample borided before and after hydrogen charged. Microstructural characterization revealed bilayer (FeB + Fe2B) coatings with saw-tooth morphology and the thicknes values of FeB and Fe2B were in range of 25.30 to 45.3 μm and 77.09 to 187.10 μm, respectively. After hydrogen charged, the microstructure delayed the diffusion of hydrogen, reducing the formation of cracks by increasing the FeB and Fe2B coatings. However. the hardness of the samples tends to increase while the elastic modulus decrease. As well as the static load by bending test decrease due to steel ASTM A-36‑hydrogen interaction. •Boride coatings were formed successfully using the dehydrated boron paste pack boriding.•The FeB/Fe2B boride coating permit to retard of the interaction of hydrogen into ASTM A-36 steel.•The effect of hydrogen on mechanical properties of the boride coatings was studied.