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2595 |
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Iron boride coatings produced by cold spray processes |
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Ismail Ozdemir* / Bartin University,Faculty of Eng.,Met. and Mater.Science Eng, Turkey Kazuhiro Ogawa / Tohoku University/Fracture and Reliability Research Institute, Japan Kazuto Sato/ Fujumi Incorporated and Tohoku University/Fracture and Reliability Research Institute, Japan Dowon Seo/ Tohoku University/Fracture and Reliability Research Institute, Japan |
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Iron based coatings have recently gained much attention as they have favorable mechanical, frictional, and corrosion properties. The coatings possessed a high content of iron borides are particularly valuable for satisfying engineering needs. Boron and iron form two major boride phases, FeB and Fe2B, with different mechanical and thermal properties. Orthorhombic boride FeB is considered to be viable candidate to enhance the surface hardness and wear resistance of components, since it has high hardness. Producing of such coating by cold spray method is considered to be an alternative for boronizing method which is a conventional thermochemical surface hardening process. In this work, the crushed ferroboron (FeB) powders of Fe-17.9B-0.4C-1.6Si-0.3Al (wt. %) were deposited onto low carbon steel substrate by cold spraying. However, low and high pressure cold spraying allowed depositing very thin and single layer on the substrate, due to the intrinsic brittleness of the powder. Therefore, several contents of Al, Ni and Fe metallic powder and their combinations were added to FeB powder to obtain thick coating via cold spray processes. Post heat treated coatings at a temperature of 900 oC resulted in increase of the hardness, possibly the formation of hard phases such as intermetallic compound. The spray powders, as-sprayed and post treated coatings were investigated systematically by DSC, SEM, EPMA, XRD and TEM. |