Nb/Ti/Zr/W对310S奥氏体不锈钢析出相行为和力学性能的影响

为了提高310S不锈钢的高温组织稳定性,本工作系统研究了微量合金化元素(Nb, Ti, Zr和W)对310S析出相行为和力学性能的影响。设计的系列合金经过1423K热轧、1423K/0.5h固溶、1173K/0.5h稳定化处理,最后进行973K/408h时效处理。研究结果表明:W可有效提高合金的高温组织稳定性,而过量Mo元素的添加会加速Cr 23 C 6向σ转变;添加Ti和Zr可细化基体晶粒,但Ti会促使时效过程中大量脆性相的析出,严重降低合金的高温组织稳定性,从而恶化合金力学性能。Fe-25Cr-22Ni-0.73Mo-0.35Nb-0.046C (质量分数/%)合金展现出优异的高温组织稳定性和力学性能(σ YS =237MPa,σ UTS =545MPa,δ=39%),有望作为超临界水冷堆核燃料包壳的候选材料。

Effect of Nb/Ti/Zr/W on precipitation behavior and mechanical property of 310S austenitic stainless steels

In order to improve the high-temperature (HT) microstructural stability of 310S-type austenitic stainless steels (ASSs), the effects of minor-alloying elements (Nb, Ti, Zr, and W) on the precipitation behaviors and mechanical properties of 310S ASSs were systematically investigated. The designed alloy ingots were hot-rolled at 1423K, solid-solutioned at 1423K for 0.5h, stabilized at 1173K for 0.5h, and then aged at 973K for different hours. The microstructure and precipitated phases at different heat-treatment states were characterized by XRD, OM, SEM-EDS and TEM, respectively. It is found that the addition of Ti or Zr can refine the matrix grains remarkably, but Ti can deteriorate the HT microstructure stability of alloy sharply, i.e ., a large amount of coarse Cr 23 C 6 and σ particles are precipitated both on GBs and in the matrix after long-term aging. In addition, the impurity of Si should be controlled strictly for the inhibition of G-Ni 16 Si 7Zr 6 phase precipitation in Zr-containing ASSs. Mo accelerates the phase transformation of Cr 23 C 6 to (during aging, while W plays an active contribution to the HT microstructure stability. The designed Fe-25Cr-22Ni-0.73Mo-0.35Nb-0.046C (mass fraction/%) alloy exhibits excellent mechanical properties (σ YS =237MPa,σ UTS = 545MPa,δ=39%) due to its higher microstructural stability at 973K, which is expected to be applied as fuel claddings.