Influence of Composite Coating (Tin/BN) On Microstructure and Properties of Laser-Cladded Martensitic Stainless-Steel Coating

Abstract

The current work used the laser cladding method to prepare a composite coating of titanium nitride (TiN) combined with boron nitride (BN) on 420 stainless steels. The microstructure, micro-hardness, wear resistance, and bio-corrosion resistance of the coatings were analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), a micro-hardness tester, a wear tester, a bio-corrosion resistance test, and electrochemical techniques. The results indicated that a strong metallurgical bond was successfully formed between the composite coating and the substrate. SEM analysis revealed that the sample produced at low power demonstrated superior performance compared to the high-power sample with respect to the microstructure. The path coefficients related to adhesion factors, such as microhardness, were higher in the low-power sample, suggesting stronger and more consistent interactions between the coating and the substrate. EDS results showed that the high-power sample had a lower iron (Fe) signal, indicating superior performance in that regard; however, the low-power sample displayed strong titanium (Ti) and BN components. Micro-hardness decreased with high power and increased with low power. The high-power sample exhibited a higher wear rate compared to the low-power counterpart. In the bio-corrosion test, the uncoated martensitic steel displayed a more negative and unstable open circuit potential (OCP) profile. In contrast, the TiN + BN-coated sample showed a less negative and more stable OCP response, indicating enhanced corrosion resistance. Electrochemical techniques demonstrated that the "Mix" sample had superior electrochemical performance compared to the "Base" sample. It exhibited a broader current density range, a higher current response, and clearer separation of anodic and cathodic reactions, making it more effective for applications in medical instruments such as orthopedic implants, dental implants (abutments and dental screws), surgical tools (scalpels, forceps, bone drills), and spinal implants and plates. Electrochemical techniques demonstrated that the "Mix" sample had superior electrochemical performance compared to the "Base" sample. It exhibited a broader current density range, a higher current response, and clearer separation of anodic and cathodic reactions, making it more effective for applications in medical instruments.