Friction and wear behaviors of Cu–15Ni–8Sn alloy fabricated by electron beam freeform fabrication

Additive manufacturing (AM) significantly shortens manufacturing workflows and provide near-net-shape capabilities. Within the domain of wear-resistant materials, high-strength, age-hardened Cu–15Ni–8Sn alloys are highly valued. However, research comparing the friction and wear properties of as-deposited (AD) and aged additively manufactured Cu–15Ni–8Sn alloys remains lacking. Therefore, this study details the distinct sliding friction characteristics of the alloy in both states and elucidates the corresponding friction and wear mechanisms. The AD Cu–15Ni–8Sn alloy exhibited a microstructure consisting of a Cu matrix with a γ segregation phase, featuring a mixture of equiaxed and columnar grains with an average size of 74.2 μm emerged in '001'||Z. Its average micro-hardness was measured as 178 HV. After solution treatment and aging (SA), the γ phase dissolved, while the D0₂₂ and L1₂ ordered phases precipitated within the matrix. The average grain size increased to 121 μm accompanied by a more randomized crystallographic orientation, and the microhardness rose significantly to 388 HV. Wear tests were conducted against GCr15 steel under dry sliding conditions at varying loads. An increase in the applied load led to a transition of the dominant wear mechanism from abrasive to delamination in both states. A pronounced difference in the wear performance between the two states was observed exclusively during the wear tests at a load of 80 N. Microstructural characterization and nanohardness measurements indicated the formation of shear bands near the wear track surface, suggesting severe localized plastic deformation during the high-load wear test. The D0₂₂ and L₁₂ ordered phases significantly enhanced the resistance to dislocation slip, and the shear band expansion increased the stability of the worn subsurface under a high frictional load. It also exhibited improved resistance to delamination and a shallower wear depth under a high applied load. This comprehensive study provides critical insights into the wear mechanisms and subsurface delamination behaviors of alloys in different states (AD and SA). Furthermore, this study offers a valuable application strategy for additively manufactured engineering materials.