FRACTURE RESISTANCE OF “TRANSITION” AREA IN THREE-LAYER STEEL/VANADIUM ALLOY/STEEL COMPOSITE AFTER THERMOMECHANICAL TREATMENT

The creation of new structural materials for cladding tubes  of fast neutron reactors is an urgent task of modern nuclear power  engineering. A three-layer radiation-resistant and corrosion-resistant material based on vanadium alloy and stainless steel, intended  for work under extreme conditions (high temperatures, radiation  and aggressive environment) of operation of fast neutron reactor  cladding tubes has been developed in recent years. The most important aspect determining the operability of this material during  operation is the quality of the joining of different materials layers  among themselves, determined by the modes of thermomechanical treatment. The effect of the annealing on the chemical composition, structure, and fracture resistance of the “steel/vanadium  alloy” interface in the steel/vanadium alloy/steel three-layer tube,  obtained by hot co-extrusion of three-layer tube billet at 1100  °C  was studied. The 20Kh13 (AISI 420 type) steel for the outer layers and V – 4Ti – 4Cr vanadium alloy for the core were used as the  components of the tube. The structure and chemical composition  in the layer joining zone were studied using the optical microscopy and electron microscopy with X-ray microspectral analysis.  The fracture resistance of the “steel/vanadium alloy” interface was  evaluated by a compression test of a three-layer ring sample with  notch using an acoustic emission (AE) measurement. It is shown  that after co-extrusion a “transition” area of diffusion interaction  having a variable chemical composition with a width of 10–15 μm  is formed between vanadium alloy and steel, which represents the  continuous series of solid solutions, without precipitation of brittle  phases, providing a strong bonding between vanadium alloy and  steel in the three-layer material. No voids, delaminations or defects 
were detected at the “steel/vanadium alloy” interface. However, a  crack is formed in the steel layer during the compression tests of  the notched semi-ring three-layer samples after hot co-extrusion.  Annealing favorably influences the formation of the “transition”  area due to the increase in the width of the diffusion interaction  area. No cracks or delaminations at the boundary between steel and  vanadium layers were observed in the three-layer tube samples after annealing, and the three-layer material behaves like a monolith  material during testing.

1. Smith D.L., Chung H.M., Loomis B.A., Witzenburg W. Van. Development of vanadium-base alloys for fusion first-wall – blanket  applications. Journal of Fusion Engineering and Design. 1995,  vol.  29, pp. 399–410.

2. Nagasaka  T.,  Muroga  T.,  Fukumoto  K.,  Watanabe  H.,  Grossbeck  M.L., Chen J. Development of fabrication technology for low  activation vanadium alloys as fusion blanket structural materials.  Nuclear Fusion. 2006, vol. 46, pp. 618–625.

3. Bray T.S., Tsai H., Nowicki L.J., Billone M.C., Smith D.L., Johnson  W.R., Trester P.W. Tensile and impact properties of V–4Cr–4Ti  alloy heats 832665 and 832864. Journal of Nuclear Materials. 2000,  vol. 283-287, pp. 633–636.

4. Votinov S.N., Kolotushkin V.P., Nikulin S.A., Turilina V.Y. Ma king  vanadium-based  radiation-resistant  alloys  for  fast-neutron  reactor pin sheaths. Metal Science and Heat Treatment. 2009, vol. 51,  pp.  238–244.

5. Rowcliffe A.F., Zinkle S.J., Hoelzer D.T. Effect of strain rate on the  tensile properties of unirradiated and irradiated V–4Cr–4Ti. Journal of Nuclear Materials. 2000, vol. 283-287, pp. 508–512.

6. Votinov S.N., Solonin M.I., Kazennov Yu.I., Kondratjev V.P. Prospects and problems using vanadium alloys as a structural material  of the first wall and blanket of fusion reactors. Journal of Nuclear Materials. 1996, vol. 233, pp. 370–375.

7. Fukumoto  K.,  Narui  M.,  Matsui  H.,  Nagasaka  T.,  Muroga  T.,  Li  M., Hoelzer D.T., Zinkle S.J. Environmental effects for irradiation creep behavior of highly purified V–4Cr–4Ti alloys (NIFSHeats) irra diated by neutrons. Journal of Nuclear Materials. 2009,   vol.  386-388, pp. 575–578.

8. Kurtz R.J., Abe K., Chernov V.M., Hoelzer D.T., Matsui H., Muroga  T., Odette G.R.. Recent progress on development of vanadium  alloys for fusion. Journal of Nuclear Materials. 2004, vol. 329-333,  pp. 47–55.

9. Muroga  T.,  Nagasaka  T.,  Abe  K.,  Chernov  V.M.,  Matsui  H.,  Smith  D.L., Xu Z.-Y., Zinkle S.J. Vanadium alloys – overview and  recent results. Journal of Nuclear Materials. 2002, vol. 307-311,  pp. 547–554.

10. Fukumoto K., Matsui H., Narui M., Yamazaki M. Irradiation creep  behavior of V–4Cr–4Ti alloys irradiated in a liquid sodium environment at the JOYO fast reactor. Journal of Nuclear Materials. 2013,  vol. 437, pp. 341–349.

11. Li X., Zhang C., Zhao J., Johansson B. Mechanical properties and  defective effects of bcc V–4Cr–4Ti and V–5Cr–5Ti alloys by firstprinciples  simulations.  Computational Materials Science.  2011,  vol.  50, pp. 2727–2731.

12. Loomis B.A., Kestel B.J., Smith D.L. Microstructural evolution and  yield stress increase for ion-irradiated V–15Cr–5Ti alloys. Journal of Nuclear Materials. 1988, vol. 155-157, pp. 1305–1309.

13. Aoyagi  K.,  Torres  E.P.,  Suda  T.,  Ohnuki  S.  Effect  of  hydrogen accu mulation on mechanical property and microstructure of   V-Cr-Ti alloys. Journal of Nuclear Materials. 2000, vol. 283-287,   pp.  876–879.

14. Chen J., Qiu S., Yang L., Xu Z., Deng Y., Xu Y . Effects of oxygen, hydrogen and neutron irradiation on the mechanical properties  of several vanadium alloys. Journal of Nuclear Materials. 2002,  vol.  302, pp. 135–142.

15. Natesan K., Soppet W.K., Uz M. Effects of oxygen and oxidation on  tensile behavior of V–4Cr–4Ti. Journal of Nuclear Materials. 1998,  vol. 258-263, pp. 1476–1481.

16. Matsushima T., Satou M., Hasegawa A., Abe K., Kayano H. Tensile  properties of a series of V–4Ti–4Cr alloys containing small amounts  of Si, Al and Y , and the influence of helium implantation. Journal of Nuclear Materials. 1998, vol. 258-263, pp. 1497–1501.

17. Heo N.J., Nagasaka T., Muroga T., Matsui H. Effect of impurity levels on precipitation behavior in the low-activation V–4Cr–4Ti Alloys. Journal of Nuclear Materials. 2002, vol. 307-311, pp. 620–624.

18. Nikulin S.A., Rozhnov A.B., Nechaikina T.A., Rogachev S.O.,  Zavodchikov  S.Yu.,  Khatkevich V.M.  Structure  and  mechanical  properties of the three-layer material based on a vanadium alloy  and corrosion-resistant steel. Russian Metallurgy (Metally). 2014,  vol.  2014, pp. 793–799.

19. Nikulin S.A., Rozhnov A.B., Nechaikina T.A., Rogachev S.O., Votinov S.N., Zavodchikov S.Yu. Combined Technique for Estimating  the Quality of Joining the Layers in Three-Layer Pipes. Russian Metallurgy (Metally). 2014, vol. 2014, pp. 347–350.

20. Khanzhin V.G. Designing computer systems for acoustic emission  materials testing. Metal Science and Heat Treatment. 2009, vol. 51,  pp. 245–249.

21. Khanzhin V.G., Nikulin S.A., Belov V.A., Turilina V.Yu., Rozhnov  A.B. Hydrogen embrittlement of steels: I. Analysis of the process kinetics using acoustic emission measurements. Russian Metallurgy (Metally). 2013, vol. 2013, pp. 308–312.

22. Nikulin S.A., Rozhnov A.B., Rogachev S.O., Nechaykina T.A., Anikeenko V.I., Turilina V.Yu. Improvement of mechanical properties  of large-scale low-carbon steel cast products using spray quenching.  Materials Letters. 2016, vol. 185, pp. 499–502.