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## Page 1
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Microstructure and properties
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of high entropy alloy coating
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obtained by laser cladding
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Di Lu1, Xiangcheng Cui1 & Jinwen Zhang2
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Corrosion remains a pivotal issue that significantly reduces the lifespan of metallic materials. Laser
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cladding technology, renowned for its exceptional effectiveness in bolstering the surface corrosion
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resistance of metal materials, has garnered considerable attention and interest. We propose utilizing
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laser cladding technology to apply a high-entropy alloy coating onto 45# steel to enhance the
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properties of the substrate. After undergoing an electrochemical test, the surface of coating was
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covered with a smooth film. The coating demonstrated exceptional corrosion resistance and adhesion
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qualities. By implementing this strategy, the corrosion resistance of 45# steel members can be
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significantly enhanced.
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Keywords Laser cladding, High entropy alloy, Corrosion resistance
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Metallic materials are extensively utilized as structural components across various sectors, including
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construction, aerospace, and automotive manufacturing1. When exposed to air or liquid, the metal’s surface
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undergoes chemical or electrochemical reactions, gradually resulting in the loss of its original performance and
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functionality, a process known as corrosion2,3. Corrosion not only shortens the lifespan of metallic materials but
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also compromises their structural integrity, posing potential safety hazards.
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The methods for enhancing the corrosion resistance of metal encompass hot-dip galvanizing, electroplating,
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spraying, and laser cladding, among others4–8. Specifically, laser cladding is an advanced technology that involves
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heating the surface of the workpiece using a high-energy laser beam and depositing the powder material onto
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this surface to form a coating9–12. Typically, the coating demonstrates exceptional wear and corrosion resistance,
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remarkable molding accuracy, and high bonding strength with the substrate.
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The type of powder material utilized in the laser cladding process is crucial in determining the performance
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of the coating. In recent years, HEAs have attracted significant attention owing to their superior performance
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across various aspects, including excellent corrosion resistance and mechanical properties13–16. Consequently,
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HEAs are anticipated to serve as an ideal raw material for laser cladding applications.
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To enhance the corrosion resistance of 45# steel components, we propose the application of laser cladding
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technology to deposit a high-entropy alloy coating onto the surface of 45# steel. In this study, we have selected
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CrMnFeCoNi as the raw material due to its excellent corrosion resistance and strong adhesive strength when
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bonded with 45# steel. Laser cladding technology has successfully prepared a well bonded corrosion resistant
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coating. This approach presents a practical and effective means of improving the surface corrosion resistance of
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45# steel.
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Methods
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Material preparation
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Powders of CrMnFeCoNi High-Entropy Alloys (HEAs), with a particle size ranging from 45 to 105 micrometers
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and gas-atomized, were employed in the laser cladding process. The chemical components of powders were
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listed in Table 1, the chemical components of substrate were also shown in this table. The powder had been
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dried first at 120 ℃ in a low vacuum oven for 1 h before were drying by vacuum oven before using. Laser
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cladding experiments were carried out utilizing a coaxial powder feed laser cladding system supplied with a
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6 kW fiber laser. The powder particles were blown from four channels, which are designed to focus the powder
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particles on the substrate surface as shown in Fig. 1. The laser beam was directed and focused onto the substrate
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surface, creating a focal spot with a diameter of approximately 1.5 mm. These experiments were conducted
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within a controlled working chamber that was saturated with argon gas, ensuring that the oxygen concentration
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1School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028, China. 2Guangdong Key
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Laboratory of Materials and Equipment in Harsh Marine Environment, Guangzhou Maritime University, Guangzhou
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510725, China. email: 18340807307@163.com; zjw@gzmtu.edu.cn
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OPEN
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Scientific Reports | (2025) 15:7357 | https://doi.org/10.1038/s41598-025-91706-5 1
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www.nature.com/scientificreports
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## Page 2
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was maintained at less than 10 ppm. Simultaneously, argon was used as a shielding gas for the laser head.
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Furthermore, we cladding a coating of HEAs to a trapezoidal groove to assess the bonding strength between the
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coating and the substrate, as illustrated on the left side of Fig. 1b.
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Microstructural characterization
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The laser-clad HEA coating’s microstructure was examined using a Zeiss Ultra 55 field-emission scanning
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electron microscopes (SEM). The corrosive agent utilized in SEM was CuSO4·5H2O+H2SO4+HCl+H2O.
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Mechanical properties testing
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Dog-bone-shaped tensile specimens, measuring 30 mm in length, 12 mm in width, and 2 mm in thickness at the
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gauge section, were obtained from the laser-clad samples through the process of electrical discharge machining.
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These specimens underwent tensile testing at room temperature on an MTS universal testing machine (model
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E43.104), with a strain rate of 1×10−1. The tensile strain was determined by dividing the total elongation
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(measured using a standard extensometer) by the initial gauge length.
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Electrochemical test
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The electrochemical test was conducted using an electrochemical workstation, employing the classical threeelectrode system. In this setup, the samples were utilized as the working electrode, while a platinum sheet served
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as the auxiliary electrode, and a reference electrode was provided by an Ag/AgCl electrode. Prior to initiating
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the corrosion test, the sample surfaces were polished to a 4000 grit smoothness using sandpaper. The test was
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performed at room temperature, with the samples submerged in a 3.5% NaCl solution. The measurements of the
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anodic polarization curve began at – 1.5 V and terminated at 1 V, employing a scan rate of 0.005 V/s.
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Result
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Microstructure
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Figure 2 depicts the cross-sectional microstructure of laser cladding coatings. Figure 2a displays a lowmagnification photograph of the crack-free cladding sample, revealing an absence of noticeable pores within the
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coating. Furthermore, there are notable distinctions between the heat affect zone and the substrate. Subsequently,
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we examined four regions with higher magnification for further analysis. According to Fig. 2b, it exhibits clear
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columnar morphology within the coating. There are a limited number of pores present within the interior,
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and no apparent cracks are visible. As depicted in Fig. 2c, it is evident that no microcracks are present in the
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vicinity of the interface between the substrate and the coating. This demonstrates that the coating and substrate
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adheres well together. From the heat affect zone to the matrix, the microstructure undergoes a transition from
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fine ferrite+granular pearlite to coarse ferrite+lamellar pearlite as shown in Fig. 2d and e. Alterations in
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microstructure can result in modifications to the mechanical properties of heat affect zone and the substrate.
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Element
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Fe
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(at%)
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Cr
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(at%)
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Mn
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(at%)
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Co
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(at%)
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Ni
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(at%)
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C
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(at%)
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P
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(at%)
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Si
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(at%)
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Substrate 97.38 0.09 1.29 - 0.17 0.47 0.14 0.46
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Powder 20.21 20.35 20.28 19.89 19.26 - - -
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Table 1. Chemical analyses of the substrate and powder.
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Fig. 1. Schematic diagram of laser clad on the 45# steel substrate.
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Scientific Reports | (2025) 15:7357 | https://doi.org/10.1038/s41598-025-91706-5 2
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## Page 3
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Mechanical property
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To confirm the bonding force between the coating and the substrate, a tensile test was conducted on the locally
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cladding sample as depicted in Fig. 3. Tensile stress is generated perpendicular to the interface during tensile
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process. The strain-stress curves of the locally cladding sample and substrate are shown in Fig. 3a. It can be
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clearly observed that compared to substrate, the yield and tensile strengths of the locally clad sample slightly
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Fig. 2. Microstructure of the cross-sectional under scanning electron microscope. microstructure. (a) Low
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magnification photograph of the cladding sample. (b), (c), (d), (e) High magnification photograph of coating,
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interface, heat affect zone and substrate respectively.
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## Page 4
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increased from 364 to 504 MPa to 431 and 535 MPa, respectively, but the elongation decreases from 16.6 to
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10.6%.
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A key finding is that the fracture in the locally clad sample starts in the substrate, as revealed in Fig. 3b. No
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failure is observed at the interface, even within the heat-affected zone. This indicates that the coating is effectively
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bonded to the substrate. During plastic deformation, the strain is not evenly distributed between the substrate
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and the cladding layer. The softer 45# steel distributes a greater strain during deformation than the harder highentropy alloy coating, so that the overall sample appears to decrease in plasticity.
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Corrosion property
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The anodic polarization curves for both the coating and the substrate were obtained in a 3.5% NaCl solution.
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In comparison to the substrate, the HEA coating exhibits a substantial improvement in corrosion resistance
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when exposed to seawater solutions, evidenced by a higher corrosion potential, as illustrated in Fig. 4. The
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corrosion potential (Ecorr) can be derived directly from the polarization curves. Compared to substrate, the
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Ecorr of the cladding increased from −1.074 to −0.775V. This significant enhancement can be ascribed to the
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abundant presence of Cr and Ni elements in the HEA coating, facilitating the development of a dense and highly
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efficacious passivation film on its surface17.
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Figure 5 presents the surface SEM image of a HEAs coating and 45# substrate after completing a polarization
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curve test in a 3.5% NaCl solution. Figure 5a characterizes the area near the pits in the HEAs coating. The
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formation of pits is attributed to the breakdown effect caused by the high potential supplied by the electrochemical
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workstation. Around the pits, the detachment of the passivation film can be observed, exposing the CrMnFeCoNi
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coating. The surface of the film is smooth and consists of numerous irregular small square-like structures, which
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exhibit strong corrosion resistance towards the substrate. It is clearly observable from Fig. 5b that the surface of
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substrate is covered with numerous tiny pits and a small amount of oxides. These oxides exhibit a porous and
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loose structure, making them prone to detachment, and thus, they are unable to form an effective and intact
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passivation film in the NaCl solution, thereby failing to provide adequate protection for the steel substrate.
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Results
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Here, HEAs coatings have been successfully fabricated utilizing laser cladding technology, exhibiting superior
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adhesion properties and corrosion resistance. The formation of smooth films during the corrosion process
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augments their corrosion resistance. Our work presents a highly practical and effective solution for enhancing
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the corrosion resistance of 45# steel.
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Fig. 3. Mechanical property of locally cladding sample and substrate. (a) Strain-stress curves of the locally
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cladding sample and substrate. (b) The fracture in the locally clad sample.
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Scientific Reports | (2025) 15:7357 | https://doi.org/10.1038/s41598-025-91706-5 4
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## Page 5
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Fig. 5. The surface SEM image of coating and 45# steel after completing a polarization curve test in a 3.5%
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NaCl solution.
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Fig. 4. Anodic polarization curve in 3.5% NaCl liquor at room temperature.
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Scientific Reports | (2025) 15:7357 | https://doi.org/10.1038/s41598-025-91706-5 5
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## Page 6
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Data availability
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Data is available on request from authors from Xiangcheng Cui through 18340807307@163.com.
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Received: 12 January 2025; Accepted: 21 February 2025
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Acknowledgements
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This work is supported by the Guangdong Province Special Funding Project for the Development of Marine
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Economy under Grant No. GDNRC [2024]41.
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Author contributions
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Di Lu: Writing – original draft, Conceptualization, Software, Methodology, Data curation.Xiangcheng Cui:
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Writing – review & editing, Supervision, Project administration, Funding acquisition, Investigation, Resources.
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Jinwen Zhang: Data curation, Funding acquisition.
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Declarations
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Competing interests
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The authors declare no competing interests.
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Additional information
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Correspondence and requests for materials should be addressed to X.C. or J.Z.
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© The Author(s) 2025
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Scientific Reports | (2025) 15:7357 | https://doi.org/10.1038/s41598-025-91706-5 6
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