Enhancing Ni–B Coatings on 42CrMo4 Steel: Effects of Magnetic Stirring and Ultrasonic Agitation on Microstructure and Corrosion Performance

Bilgin S., Topal S., Usta Y. E., Yildiz U. T., Alver Ü., Sünbül S. E., ...More

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, vol.56, no.8, pp.3111-3124, 2025 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 56 Issue: 8
  • Publication Date: 2025
  • Doi Number: 10.1007/s11661-025-07810-8
  • Journal Name: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, PASCAL, Aerospace Database, Applied Science & Technology Source, Chemical Abstracts Core, Communication Abstracts, Compendex, Computer & Applied Sciences, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.3111-3124
  • Karadeniz Technical University Affiliated: Yes

Abstract

Abstract: This study explores the development of electroless nickel–boron (Ni–B) coatings on AISI4140 steel using sodium borohydride as a reducing agent, employing ultrasonic agitation and magnetic stirring. Electroless plating is preferred for its cost-effectiveness and ability to coat complex geometries. The Ni–B coated on 42CrMo4 steel was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), microhardness measurements, and electrochemical corrosion properties. The analysis reveals that magnetic stirring yields a thicker, more homogeneous coating with a characteristic cauliflower morphology. In contrast, ultrasonic agitation produces coatings with a mix of columnar and nodular structures. Corrosion resistance tests in NaCl solution show enhanced performance of Ni–B-coated samples over bare steel. The corrosion current density of 42CrMo4 steel is 9.44 × 10−6 A/cm2. The corrosion current densities of the samples coated with magnetic stringing and ultrasonic agitation decreased by 1.38 × 10−6 and 1.03 × 10−6 A/cm2, respectively, increasing their corrosion resistance. This study highlights the significant impact of different stirring methods on the microstructural properties, surface quality, and corrosion resistance of Ni–B coatings.