Effect of heat treatment on microstructure and mechanical properties of laser cladded high Co-Ni steel coating
The effect of post-heat treatment on the microstructure and microhardness of laser cladded high Co-Ni secondary hardening steel coating was investigated.The microstructure of the coating was analyzed using a scanning electron microscopy(SEM)equipped with an energy dispersive spectrometer(EDS),and the microhardness was measured with a Vickers indenter.Decomposition of the retained austenite in the coating occurred during the post-heat treatment.As the temperature increased from 200 ℃ to 600 ℃,the quantity of the retained austenite at the boundaries decreased significantly,while that of the needle-shaped M3C cementite and M2C carbides increased.The M2C carbides evidently coarsened when the temperature was 550 ℃ and 600 ℃.The microhardness of high Co-Ni steel coating increased as the temperature of heat treatment increased from 200 ℃ to 400 ℃ because the fine-scale M2C carbides were coherent with the matrix and increased distinctly in this temperature range.While the microhardness decreased sharply when the temperature was improved from 500 ℃ to 600 ℃ due to both the incoherency of the coarsened M2C carbides and the recovery of dislocations in the carbon-supersaturated matrix.
NETL
NSTL
万方数据
