Superior corrosion resistance-dependent laser energy density in (CoCrFeNi)95Nb5 high entropy alloy coating fabricated by laser cladding

Abstract

CoCrFeNi) 95 Nb 5 high entropy alloy (HEA) coatings were successfully fabricated on a substrate of Q235 steel by laser cladding technology. These (CoCrFeNi) 95 Nb 5 HEA coatings possess excellent properties, particularly corrosion resistance, which is clearly superior to that of some typical bulk HEA and common engineering alloys. In order to obtain appropriate laser cladding preparation process parameters, the effects of laser energy density on the microstructure, microhardness, and corrosion resistance of (CoCrFeNi) 95 Nb 5 HEA coating were closely studied. Results showed that as the laser energy density increases, precipitation of the Laves phase in (CoCrFeNi) 95 Nb 5 HEA coating gradually decreases, and diffusion of the Fe element in the substrate intensifies, affecting the integrity of the (CoCrFeNi) 95 Nb 5 HEA. This decreases the microhardness of (CoCrFeNi) 95 Nb 5 HEA coatings. Moreover, the relative content of Cr 2 O 3 , Cr(OH) 3 , and Nb 2 O 5 in the surface passive film of the coating decreases with increasing energy density, causing corrosion resistance to decrease. This study demonstrates the controllability of a high-performance HEA coating using laser cladding technology, which has significance for the laser cladding preparation of other CoCrFeNi-system HEA coatings.

High Entropy Alloys Coatings Deposited by Laser Cladding: A Review of Grain Boundary Wetting Phenomena

“…The Laves phase completely separated the fcc grains at 100 J/mm 2 . With increasing E the portion of completely wetted fcc/fcc GBs continuously decreased from ~100% at 100 J/mm 2 to only ~10% at 167 J/mm 2 [72]. Thus, the increase of laser beam power corresponds in the framework of our scheme to the shift of T wmin value to higher temperatures.…”

“…The Laves phase completely separated the fcc grains at 100 J/mm 2 . With increasing E the portion of completely wetted fcc/fcc GBs continuously decreased from ~100% at 100 J/mm 2 to only ~10% at 167 J/mm 2 [72]. Thus, the increase of Figure 11 shows the SEM images for the microstructure of ((CoCrFeNi) 95 Nb 5 ) 99 Mo 1 HEA coatings (i.e., for x = 1) deposited with different laser beam power, namely 800, 1000 and 1200 W. It is clearly visible that as a result of the increase of laser beam power a transition of complete GB wetting to incomplete wetting takes place (compare Figure 11b,c for 800 and 1000 W, respectively).…”

“…In Ref. [72], the (CoCrFeNi) 95 Nb 5 HEA coating was deposited with laser energy densities E of 100, 111, 125, 143, and 167 J/mm 2 . The coatings have the fcc phase as a matrix and minor Laves phase.…”

Design of High-Entropy Alloy Coating for Cavitation Erosion Resistance by Different Energy-Induced Dynamic Cyclic Behaviors

“…Thanks to its high entropy, lattice distortion, sluggish diffusion, and cocktail effects, the single FCC high-entropy alloy (HEA) can combine low SFE, moderate hardness, excellent oxidation resistance, and corrosion resistance that cannot be achieved by traditional metal materials, − so it is expected to be used as the next-generation anti-CE material. Of note, with the rapid development of gas atomization technology and advanced surface technology, the preparation of HEA coatings on the surface of large fluid machinery has been in the forefront of research because it is more economical and effective. , …”

“…Of note, with the rapid development of gas atomization technology and advanced surface technology, the preparation of HEA coatings on the surface of large fluid machinery has been in the forefront of research because it is more economical and effective. 28,29 Bearing those perspectives in mind, in the present research, we proposed a bold and novel approach to design CE-resistant HEA coatings: first, four elements, Al, Co, Cr, and Ni, which have outstanding oxidation and corrosion resistance and high melting points, were selected to prepare a new HEA coating with single FCC structure and moderate hardness by optimizing thermodynamic and topological parameters, so as to avoid the material surface being seriously melted or oxidized by cavitation heat; second, the low SFE of the FCC structure was expected to make this coating prone to produce mechanical response behaviors such as grain refinement, dislocation, and martensitic transformation under the action of cavitation load, so as to better absorb mechanical impact energy and produce work hardening; third, these refined grains and defect structures were expected to achieve growth and structural relaxation by absorbing cavitation heat, so as to dissipate heat energy and delay the embrittlement trend of the surface layer. That is, through the scientific design of the material component structure, the response behaviors of surface grains caused by cavitation load and heat were expected to be transformed or/and counteracted each other, which led to the elimination and dissipation of two kinds of energies, so as to achieve the purpose of significantly inhibiting CE damage.…”