NiTi coating formation on Ti for enhanced wear resistance utilizing electron-beam additive manufacturing technique

• A novel coating method via electroplating and electron beam scanning was developed. • NiTi coatings were formed on wear-prone pure Ti by this method with Ni-plating. • The coatings achieved wear resistanse comparable to that of superelastic NiTi alloy. • The method can be used for Ti components needing the improvment of wear-resistance. Titanium and its alloys are extensively utilized in various industries owing to their high corrosion resistance and excellent strength-to-weight ratio. However, their poor wear resistance limits further applications. The present study developed a novel method to fabricate wear-resistant NiTi coatings on commercially pure titanium (CP-Ti) substrates to overcome this limitation. The process comprises electroplating a pure Ni layer followed by fusion with the CP-Ti substrate by electron beam (EB) scanning. The surface roughness and composition of the coating can be fine-tuned by adjusting the EB irradiation conditions. For example, the average roughness of continuously scanned (CS) coatings is R a 8.9, while the average roughness of intermittently scanned (IS) coatings is reduced by 60% compared to CS-coatings. Additionally, the Ni concentration in the IS-coatings can be finely adjusted from 45 at.% to 55 at.% by adjusting EB power. X-ray diffractometry (XRD) revealed that IS-coatings are partially composed of superelastic B 2-NiTi phases. Nanoindentation and sliding wear tests demonstrated that the hardness-to-modulus ( H / E ) ratio and depth recovery ratio ( η d,h ) of the IS-coating increased by a factor of 4.7 and 2.9 compared to those of CP-Ti, respectively. Additionally, the specific wear rate ( W s ) of the IS-coating was reduced by 80% compared to CP-Ti. The mechanical properties of the IS-coating were comparable to those of superelastic NiTi alloy. This newly developed method offers potential applications beyond NiTi coatings, enabling the development of various functional coatings for enhanced wear resistance.