Achieving illustrious friction on a directed energy deposition 316/NiTi heterogeneous alloy with bionic Ni interlayer

[Display omitted] •The sandwich structure of 316-Ni-NiTi specimens was designed and prepared by introducing the Ni interlayer.•The microstructure and microhardness of 316-Ni-NiTi along the building direction were investigated.•The wear mechanism of the substrate and 316-Ni-NiTi coating under different loads was revealed. The high brittleness intermetallic compound Fe2Ti is a key obstacle in joining stainless steel and NiTi alloys. In this study, Ni interlayer are introduced to prepare 316-Ni-NiTi multi-material specimens by direct energy deposition to reduce the excessive Fe2Ti in the system while improving the wear resistance of 316 under different loads. The presence of Ni interlayer reduces intermetallic compound Fe2Ti, resulting in the composition of 316-Ni-NiTi phase dominated by NiTi and Ni3Ti. The microstructure shows a typical dendritic morphology, in which eutectic regions existed in the NiTi layer. Both the 316/Ni interface and the Ni/NiTi interface exhibits good metallurgical bonding, the occurrence of the mutual diffusion phenomenon is confirmed by quantitative and qualitative analysis of the chemical composition of the 316-Ni-NiTi specimens. The average microhardness of the NiTi layer is 770 HV, which is 4.9 times higher than the 316, which benefiting from the intermetallic compound with high hardness generated by the introduction of the Ni interlayer. The wear weight loss of the 316-Ni-NiTi coating is less than that of the substrate at different loads, especially at a load of 60 N, which is only 29% of the substrate.