Abstract:Low diffusion efficiency and porous layer are two important problems in chromeizing production. In this paper, cr-permeable coating was prepared on GCr15 surface by solid embedding method. The growth mechanism of permeable layer, pore formation and the effect of different rare earth oxides on permeable layer were discussed. The results show that the permeability layer thickness increases obviously after adding rare earth oxides, and the permeability efficiency of the three rare earth oxides is Y2O3> CeO2> La2O3. The Cr permeable layer is obviously divided into two layers, the outer layer is porous layer dominated by (Cr, Fe)23C6 phase, and the inner layer is dense layer dominated by (Cr, Fe)7C3 phase. The (Cr, Fe)23C6 phase layer, which is first generated on the substrate surface at the early stage of diffusion, inhibits the inward diffusion of active Cr atoms and promotes the growth of the tight layer as a Cr source. The difference in the diffusion rate of Cr atoms and the stress in the permeable layer are the main reasons for the formation of pores. It is found that reducing the carbon content of substrate inhibits the formation of (Cr, Fe)23C6 phase layer or refining the grain of the phase layer to increase the diffusion channel of Cr atom can effectively reduce the porosity, which provides an important idea for improving the quality of chromizing layer.