淬火温度对25Cr3MoA钢脉冲渗氮组织和性能的影响

Effect of Quenching Temperature on Microstructure and Properties of Pulse Nitriding of 25Cr3MoA Steel

采用不同温度淬火+600℃回火对25Cr3MoA钢进行渗氮前处理,对不同调质处理后的25Cr3MoA钢进行真空脉冲气体渗氮试验,并研究其组织、表面硬度、渗氮层硬度梯度和脆性等。结果表明:25Cr3MoA钢经不同温度淬火后,其板条状马氏体和残留奥氏体组织随淬火温度的升高逐渐变粗大,粗化温度为950℃;随着淬火温度升高,25Cr3MoA钢渗氮后白亮层厚度增加,渗氮层组织变粗大;淬火温度为900℃时,白亮层厚度为10~15μm,渗氮层晶粒尺寸较小,渗层组织较均匀;25Cr3MoA钢渗氮层深度随着淬火温度的升高而增加,渗氮层组织明显变粗大。综合分析不同温度淬火后的材料渗氮层组织、结构和性能,25Cr3MoA钢渗氮前的淬火温度建议为900℃。

25Cr3MoA steel was treated using different quenching temperatures and 600℃tempering before the nitriding treatment.Then,the vacuum pulse gas nitriding tests were conducted on the 25Cr3MoA steel after the different quenching and tempering treatments.The microstructure,surface hardness,and the hardness gradient and brittleness of the nitrided layer were studied.The results show that the lath martensite and retained austenite structure of 25Cr3MoA steel after quenching at different temperatures became coarser with the increase of quenching temperature,and the coarsening temperature is 950℃.As the quenching temperature raised,the thickness of white bright layer of nitrided 25Cr3MoA steel increased,and the microstructure of nitrided layer became coarser.When the quenching temperature is 900℃,the thickness of the white bright layer is about 10~15μm.At this condition,the grain size of nitrided layer is small,and its microstructure is relatively uniform.Also,the nitrided layer depth increased with the rise of quenching temperature,and the microstructure of the nitrided layer became significantly coarser.Based on the comprehensive analyses results of the microstructure,structure,and properties of the nitrided layer with different quenching temperatures,it can be concluded that 900℃is a proper quenching temperature for 25Cr3MoA steel before nitriding.