Laser surface alloying of Ti with Cr/Mo enabling dissimilar Ti-Cr joints using additive manufacturing concept approach

Dissimilar metal joints often fail due to the formation of brittle intermetallic phases at the interface. This study demonstrates a practical strategy to join titanium (Ti) and chromium (Cr) using laser surface alloying with molybdenum (Mo) as an intermediate layer. Single tracks and thin coatings of Cr and Mo were deposited on commercially pure Ti using a custom powder bed system that mimics key powder bed fusion parameters: laser power 150–450 W, scan speed 10 mm/s, beam diameter ∼254 µm, powder layer thickness 0.25 mm, and 50% overlap. Microstructure and composition were analysed by SEM-BSE/EDS and XRD, while hardness and Young’s modulus were measured by instrumented indentation. Cr-only deposits showed cracking near the fusion boundary, linked to brittle Ti-Cr intermetallics and residual stress. In contrast, Mo-only coatings were crack-free and promoted β-Ti stabilisation. A bilayer design (Ti/Mo+Cr) produced a continuous, crack-free modified zone. Mo acted as a compatibility layer, improving dilution and allowing the top Cr layer to form a Cr-Mo solid solution above metastable β-Ti. The Ti-Mo-Cr surface exhibited higher hardness than the substrate without the embrittlement seen in Ti-Cr alone. These findings show that a Mo interlayer can enable sound Ti-Cr joints in additive manufacturing.