Superior wear resistance in NiW750 alloy through the combined architecture of nanoprecipitation and composite gradient nanostructure

Medium-heavy alloys, such as NiW750 alloy, are expected with superior wear resistance for applying as warhead materials in extreme conditions. In this work, a novel processing route of forging → solid solution → ultrasonic shot peening (USP) → aging (simplified as FSUA) is proposed to construct a combined architecture of nanoprecipitation and composite gradient nanostructure (NP-CGNS) in NiW750 alloy for achieving exceptional wear resistance. Tensile and hardness tests demonstrate an improvement in strength-ductility combination and surface hardness under FSUA treating, and yields the optimal USP treatment duration of 6 min (deemed as FSUA-6) which induces the most desirable properties. NP-CGNS structure is observed in FSUA-6 with a hardened layer depth exceeding 500 μm, co-consisted of gradient nanograin, gradient nanotwin, gradient dislocation structure, and higher number density of finer Ni₄W nanoprecipitates. Relative to non-USP treated (deemed as FSUA-0) counterpart, FSUA-6 yields reductions in the average COF and wear rate by 48 % and 42.8 %, respectively. Characterization on worn surfaces reveals reduced delamination, spalling, and oxidation phenomena, and a refinement in wear debris in FSUA-6, along with decreases on surface roughness parameters of Ra and Rmax by 75 % and 86 %, respectively. The improvement in wear behavior is mainly arise from the hierarchical strengthening of NP-CGNS, which resist plastic deformation, crack initiation and propagation during wear. This study provides fresh strengthening strategy and technology pathway for fabricating superior wear-resistant medium heavy alloys.