Mechanical and Structural Characterization of Laser-Cladded Medium-Entropy FeNiCr-B4C Coatings

• Published in: Materials 2023-08, Vol.16 (15), p.5479
• Main Authors: Okulov, Artem, Korobov, Yury, Stepchenkov, Alexander, Makarov, Aleksey, Iusupova, Olga, Korkh, Yulia, Kuznetsova, Tatyana, Kharanzhevskiy, Evgeny, Liu, Kun
• Format: Article
• Language: English
• Subjects: Boron carbide; Coatings; Corrosion resistance; Deformation; Dislocation density; Ductility; Entropy; Face centered cubic lattice; Grains; Interlayers; Laser beam cladding; Lasers; Manufacturers; Manufacturing; Mechanical properties; Medium carbon steels; Microhardness; Microstructural analysis; Protective coatings; Pulsed lasers; Raman spectroscopy; Spectrum analysis; Structural analysis; Substrates
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16155479

Equiatomic medium-entropy alloy (MEA) FeNiCr-B4C (0, 1, and 3 wt.% B4C) coatings were deposited onto an AISI 1040 steel substrate using pulsed laser cladding. Based on an SEM microstructural analysis, it was found that the cross-sections of all the obtained specimens were characterized by an average coating thickness of 400 ± 20 μm, a sufficiently narrow (100 ± 20 μm) “coating–substrate” transition zone, and the presence of a small number of defects, including cracks and pores. An XRD analysis showed that the formed coatings consisted of a single face-centered cubic (FCC) γ-phase and the space group Fm-3m, regardless of the B4C content. However, additional TEM analysis of the FeNiCr coating with 3 wt.% B4C revealed a two-phase FCC structure consisting of grains (FCC-1 phase, Fm-3m) up to 1 µm in size and banded interlayers (FCC-2 phase, Fm-3m) between the grains. The grains were clean with a low density of dislocations. Raman spectroscopy confirmed the presence of B4C carbides inside the FeNiCr (1 and 3 wt.% B4C) coatings, as evidenced by detected peaks corresponding to amorphous carbon and peaks indicating the stretching of C-B-C chains. The mechanical characterization of the FeNiCr-B4C coatings specified that additions of 1 and 3 wt.% B4C resulted in a notable increase in microhardness of 16% and 38%, respectively, with a slight decrease in ductility of 4% and 10%, respectively, compared to the B4C-free FeNiCr coating. Thus, the B4C addition can be considered a promising method for strengthening laser-cladded MEA FeNiCr-B4C coatings.