Enhanced carburization efficiency and performance of vacuum carburized layers by La2O3-doped supersonic fine particle bombardment

Abstract

In this work, the fabrication of supersonic fine particle bombardment (SFPB)-doped rare-earth pretreatment modified vacuum carburized layers were applied. The SFPB-doped La2O3 pretreated vacuum carburized reinforced layer was explored by common testing methods such as XRD, XPS, SEM, and TEM, focusing on the effects of La2O3-doped SFPB pretreatment on the decomposition, adsorption and diffusion of active carbon atoms and the diffusion mechanism. The composite carburizing behavior of La2O3-doped SFPB pretreatment modified layer under the action of thermal coupling is explored, and the influence law of rare earth modified carburizing and nano-modified carburizing on the thickness, residual stress, impact toughness, tribological properties of the carburized layer were clarified. The mechanism of mass transfer under the coupling role of pre-set surface defects and rare earth pinning was revealed. The case depth of the LSPC layer was increased by 14.3%, and the residual stress was significantly higher. The carbon diffusion coefficients of LSPC were 1.31 times superior to that of the vacuum carburizing layer, which is mainly attributed to the formation of a large number of nanocrystals with high-angle grain boundaries (HAGBs) by the rare-earth doped nanosized pretreatment, and the multiple synergistic strengthening effects of rare-earth oxides and nanocrystals.