Damage evolution and plastic deformation mechanism of passivation layer during shear rheological polishing of polycrystalline tungsten

Abstract

Aiming at the problems of low processing efficiency and uneven material removal during shear rheological polishing (SRP) of polycrystalline tungsten, this paper introduces the Fenton-like reaction between H2O2 and Cu2+ to enhance the chemical effect on material removal. Passivation behavior and removal mechanisms were investigated using electrochemical tests, scanning electron microscopy, atomic force microscopy, and other characterization methods. Results show that the Fenton-like reaction exhibits excellent activity under the combined action of H2O2 and Cu(NO3)2, obtaining a satisfactory material removal rate of 702.22 Å⋅min−1 and a surface roughness Rq of 7.05 nm. The efficacy of the H2O2+Cu(NO3)2 slurry lies in its superior removal and passivation performance, attributed to the generation of hydroxyl radicals through the Fenton-like reaction. These radicals facilitate the formation of a WO3 passivation layer with good corrosion resistance on the surface, while enabling easy removal through mechanical wear. In addition, the plastic deformation mechanism of passivation layer was also studied by nanoscratch tests and transmission electron microscopy. It is found that a pure plastic flow groove can be obtained in the load range of 3–100 mN, accompanied by the formation of asymmetric deformation and pile-ups in the subsurface of the main plastic zone.