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本文研究了25cr2Mov钢经调质并深层渗氮后发生的脆化现象及临界区热处理对抑制氮化期脆化的作用。试验结果表明,试样调质后,在深层渗氮期间的长期回火作用引起了回火脆性。其表现为钢材脆性转化温度(FATT)明显升高,室温冲击断口呈现沿晶断裂特征。对脆化试样断口的俄歇电子谱仪分析(AES)证实了磷在奥氏体晶界的偏聚。而试样先经临界区热处理然后再进行渗氮,则脆性转化温度降低,在-40℃下仍呈韧窝状断口。其原因是经临界区处理后,显著细化了组织与晶粒以及钢中存在着一部分铁素体相,它们均有效地使晶界上杂质元素的偏聚程度降低,从而减轻了晶界脆化。此外临界区热处理减少晶界碳化物的析出,也有利于保持韧性。
In this paper, the brittleness of 25cr2Mov steel after quenching and deep nitriding and the effect of critical zone heat treatment on the inhibition of nitriding embrittlement were studied. The test results show that the tempering brittleness caused by long-term tempering during deep nitriding after the sample is tempered. The results showed that the brittle transition temperature (FATT) of steel increased obviously, and the fracture at room temperature showed the intergranular fracture characteristics. Auger electron spectroscopy (AES) of the fracture of the embrittled specimen confirmed the segregation of phosphorus at the austenite grain boundaries. The sample first by the critical zone heat treatment and then nitriding, the brittle transition temperature decreased at -40 ℃ was still dimple fracture. The reason is that after the critical zone treatment, the microstructure and grain refinement and the existence of a part of the ferrite phase in the steel are effectively reduced the degree of segregation of the impurity elements on the grain boundary, thereby reducing the grain boundary brittleness The In addition, the critical zone heat treatment to reduce the grain boundary carbide precipitation, but also conducive to maintaining toughness.