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5375 |
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Thursday, June 08, 2017, Hall 27 1:40 PM Pre- & Post-Treatment |
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Wear-resistant iron-based coatings using a modified gas nitriding process as thermochemical post heat treatment |
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Pia Kutchmann / Chemnitz University of Technology, Germany Thomas Lindner / IWW, TU Chemnitz, Germany Kristian Börner/ Härterei Reese Chemnitz GmbH & Co. KG, Deutschland Ulrich Reese/ Härterei Reese Chemnitz GmbH & Co. KG, Deutschland Thomas Lampke/ IWW, TU Chemnitz, Deutschland Thomas Grund*/ Chemnitz University of Technology, Germany |
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The present study shows preliminary results of thermochemical post-treatment applied for thermally sprayed coatings. The thermochemical near-surface processes are limited to bulk materials up to now. The combination of thermal spray technique with a subsequent gas nitriding process intends to result in a wear improvement with concurrent good corrosion behaviour of iron-based coatings. High-alloyed, ferritic and austenitic steels are chosen as coating materials. In the subsequent gas nitriding process, the porosity of the thermally sprayed coatings is utilized to achieve an even enrichment of nitrogen with a high depth effect. This is realised by using a pressure modulation of the donor media. The conducted study revealed that iron-based, thermally sprayed coatings could be gas nitrided without prior activation of the surface. The realised depth effect of the nitriding process is dependent on the coating microstructure, which was varied by applying different thermal spray processes, APS, HVOF and arc spraying. The increased hardness in the near-surface area of the coatings was verified by hardness measurements on the cross-sections. The improved wear resistance in comparison to the untreated coatings was proved by ball-on-disc and oscillating wear tribometer tests. At last, the existent phases in the surface-near area of the coatings were characterized by X-ray diffraction. |