Steam oxidation of thermally deposited coatings from 304 L and recycled 316 L/Z100 steels: Influence of temperature, coatings microstructure and steel recycling
{"title":"Steam oxidation of thermally deposited coatings from 304 L and recycled 316 L/Z100 steels: Influence of temperature, coatings microstructure and steel recycling","authors":"","doi":"10.1016/j.surfcoat.2024.131478","DOIUrl":null,"url":null,"abstract":"<div><div>The application of thermally sprayed stainless steels coatings is a well-established approach to protecting low-alloy steels against high-temperature degradation. In this study, we investigated both: (1) the influence of microstructural features of the coatings and (2) the recycling of stainless steels on the course of high temperature steam oxidation. It was achieved by thermally spraying coatings on C45 steel from 304 L and a new type of 316 L/Z100 steel, obtained as a result of mixed scraps recycling. Steam oxidation tests carried out in the temperature range 600–800 °C for 500 h in pure steam show temperature depended mechanism of oxidation, which was defined and described. The formation of the scales with a multi-layered structure was observed, consisting of Fe<sub>2</sub>O<sub>3</sub>, Fe<sub>3</sub>O<sub>4,</sub> Cr<sub>2</sub>O<sub>3</sub>, Fe- or Cr-rich Cr<sub>x</sub>Fe<sub>x-2</sub>O<sub>3</sub> and (Mn,Cr,Ni)<sub>x</sub>Fe<sub>3-x</sub>O<sub>4</sub> spinels. The relative ratio of the phases and their presence in particular scale layers varied depending on the material studied and the exposure temperature. The key findings are that recycling of steel deposited as protective coating has led to an unintended change in Si and C concentrations, which may affects course of oxidation. Also, the microstructure of the initial coatings, consisting of porosity and a significant volume of oxides formed during steel deposition, inhibits the formation of a homogeneous layer of protective Cr<sub>2</sub>O<sub>3</sub>. As a result, the established values of oxidation kinetics constants (in range of 8.55E-12 to 1.50E-10 g<sup>3</sup>·cm<sup>−6</sup>·s<sup>−1</sup> for 316 L/Z100 and 2,71E-12 to 4.60E-10 g<sup>3</sup>·cm<sup>−6</sup>·s<sup>−1</sup> for 304 L coatings) and oxidation activation energies (156.4 kJ·mol<sup>−1</sup> for 316 L/Z100 and 211.5 kJ·mol<sup>−1</sup> for 304 L coatings) differ significantly from those of bulk steels under the same conditions reported in the literature.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":null,"pages":null},"PeriodicalIF":5.3000,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Surface & Coatings Technology","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0257897224011095","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, COATINGS & FILMS","Score":null,"Total":0}
引用次数: 0
Abstract
The application of thermally sprayed stainless steels coatings is a well-established approach to protecting low-alloy steels against high-temperature degradation. In this study, we investigated both: (1) the influence of microstructural features of the coatings and (2) the recycling of stainless steels on the course of high temperature steam oxidation. It was achieved by thermally spraying coatings on C45 steel from 304 L and a new type of 316 L/Z100 steel, obtained as a result of mixed scraps recycling. Steam oxidation tests carried out in the temperature range 600–800 °C for 500 h in pure steam show temperature depended mechanism of oxidation, which was defined and described. The formation of the scales with a multi-layered structure was observed, consisting of Fe2O3, Fe3O4, Cr2O3, Fe- or Cr-rich CrxFex-2O3 and (Mn,Cr,Ni)xFe3-xO4 spinels. The relative ratio of the phases and their presence in particular scale layers varied depending on the material studied and the exposure temperature. The key findings are that recycling of steel deposited as protective coating has led to an unintended change in Si and C concentrations, which may affects course of oxidation. Also, the microstructure of the initial coatings, consisting of porosity and a significant volume of oxides formed during steel deposition, inhibits the formation of a homogeneous layer of protective Cr2O3. As a result, the established values of oxidation kinetics constants (in range of 8.55E-12 to 1.50E-10 g3·cm−6·s−1 for 316 L/Z100 and 2,71E-12 to 4.60E-10 g3·cm−6·s−1 for 304 L coatings) and oxidation activation energies (156.4 kJ·mol−1 for 316 L/Z100 and 211.5 kJ·mol−1 for 304 L coatings) differ significantly from those of bulk steels under the same conditions reported in the literature.
期刊介绍:
Surface and Coatings Technology is an international archival journal publishing scientific papers on significant developments in surface and interface engineering to modify and improve the surface properties of materials for protection in demanding contact conditions or aggressive environments, or for enhanced functional performance. Contributions range from original scientific articles concerned with fundamental and applied aspects of research or direct applications of metallic, inorganic, organic and composite coatings, to invited reviews of current technology in specific areas. Papers submitted to this journal are expected to be in line with the following aspects in processes, and properties/performance:
A. Processes: Physical and chemical vapour deposition techniques, thermal and plasma spraying, surface modification by directed energy techniques such as ion, electron and laser beams, thermo-chemical treatment, wet chemical and electrochemical processes such as plating, sol-gel coating, anodization, plasma electrolytic oxidation, etc., but excluding painting.
B. Properties/performance: friction performance, wear resistance (e.g., abrasion, erosion, fretting, etc), corrosion and oxidation resistance, thermal protection, diffusion resistance, hydrophilicity/hydrophobicity, and properties relevant to smart materials behaviour and enhanced multifunctional performance for environmental, energy and medical applications, but excluding device aspects.