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