Alloying Element Depletion and Phase Transition in Stainless Steel 304 Induced by PEO Treatment in KOH- and TaOH-Rich Electrolyte

Due to their lower cost and good mechanical and corrosion properties, ferrous materials such as stainless steel (SS) are commonly used as bio-materials, mainly as surgical instruments and implants. Surface treatments such as plasma electrolytic oxidation (PEO) can be a valuable tool to increase corr...

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Bibliographic Details
Main Authors: João Paulo de Proença, Rafael Parra Ribeiro, Elidiane Cipriano Rangel, Nilson Cristino da Cruz, Bruna de Oliveira Pinto, Carlos Roberto Grandini, Diego Rafael Nespeque Correa
Format: Article
Language:English
Published: MDPI AG 2023-10-01
Series:Crystals
Subjects:
Online Access:https://www.mdpi.com/2073-4352/13/10/1480
Description
Summary:Due to their lower cost and good mechanical and corrosion properties, ferrous materials such as stainless steel (SS) are commonly used as bio-materials, mainly as surgical instruments and implants. Surface treatments such as plasma electrolytic oxidation (PEO) can be a valuable tool to increase corrosion resistance and enhance the bio-compatibility of metallic materials. In this scenario, the current study evaluated the effect of electrolyte composition on the surface of SS304 submitted to PEO treatment. The variation in the amount of KOH and Ta(OH)<sub>5</sub> promoted significant changes in the surface characteristics, forming Fe-rich oxide plates, Ta-rich agglomerate particles, and an exposed substrate. The PEO-treated substrates were depleted of some alloying elements (Cr, Ni, and Mn), which, allied to the Ta-enrichment, affected the roughness, wettability, phase stability, micro-hardness, and corrosion resistance. All the PEO treatments presented a phase composition of single γ-Fe instead of a dual α + γ phase from the untreated substrate, which was understood in terms of the Ni<sub>eq</sub>-Cr<sub>eq</sub> diagram. The corrosion tests indicated that the PEO treatment significantly affected the corrosion parameters, having the presence of a non-uniform oxide layer. The findings show that it is possible to control the chemical and phase composition of SS304 material employing PEO treatment.
ISSN:2073-4352