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通过稀土化学热处理和第一性原理计算方法研究了纳米化3 J33钢在500℃脉冲等离子体稀土氮碳共渗4h时共渗层的相结构和硬度分布以及共渗相的性质。结果表明,共渗层由厚度约5μm的化合物层和90μm的扩散层组成;共渗相主要由γ′-Fe4N和含碳氮的α′-Fe相组成;与纳米化的3 J33钢相比,渗层表面硬度提高约1倍,基体时效后硬度也有所提高。计算结果表明,在共渗过程中γ′-Fe4N相较α′-Fe相更容易形成,但α′-Fe相更加稳定;γ′-Fe4N相的硬度高于α′-Fe相的硬度的主要原因是γ′-Fe4N相的N-Fe键较α′-Fe相的C-Fe键更强;此外,γ′-Fe4N相的体模量与剪切模量的比值大于1.75,因此该相具有延性。
The phase structure and hardness distribution and the properties of co-infiltrating phase of nanocrystallized 3 J33 steel were investigated by rare earth chemical heat treatment and first-principles calculations after pulsed plasma nitrocarburizing at 500 ℃ for 4 h. The results show that the co-diffusion layer consists of a compound layer with a thickness of about 5 μm and a diffusion layer with a thickness of 90 μm. The co-permeation phase mainly consists of γ’-Fe4N and carbon-nitrogen-containing α’-Fe phases. Compared with the nano-sized 3 J33 steel , The surface hardness of the infiltrated layer is increased by about 1 time, and the hardness of the matrix after aging is also improved. The results show that the γ’-Fe4N phase is easier to form than the α’-Fe phase during the infiltration process, but the α’-Fe phase is more stable. The hardness of the γ’-Fe4N phase is higher than the hardness of the α’-Fe phase The main reason is that the N-Fe bond in the γ’-Fe4N phase is stronger than the C-Fe bond in the α’-Fe phase. In addition, the ratio of the bulk modulus to the shear modulus of the γ’-Fe4N phase is larger than 1.75, Phase has ductility.