GRADIENT STRUCTURE OF THE LAYER FACED ON HARDOX 450 STEEL WITH Fe –С–Cr–Nb–W POWDER WIRE AND MODIFIED BY ELECTRON BEAM PROCESSING

In recent years, the attention of researches in the field of physical materials science is focused on the study of facing of composite coatings hardened with the particles of carbides, borides and other high solid phases. The principal factor determining the service properties of the faced layers is phase composition of coating materials. In order to make substantiated choice of coating material corresponding to the conditions of their extreme service, high loads and abrasive wear it is necessary to carry out thorough studies of their properties and structure. Structure-phase states and tribological properties of coating faced on Hardox  450 martensite low carbon steel with Fe – C – Cr – Nb – W powder wire and modified by subsequent electron beam processing were studied in the research using methods of modern materials science. The regime of electron beam processing is the following: parameters of electron beam at the first stage – energy density of electron beam in pulse E_S   =  30  J/cm² , duration of pulses τ  =  200  µs, number of pulses N  =  20; at the second stage – E_S   =  30  J/cm² , τ  =  50  µs, N  =  1. The regimes of irradiation were chosen based on calculation results of temperature field being formed in surface layer of material in one pulse regime irradiation. It is shown that electron beam processing of ~5  mm thick faced layer results in formation of ~20  µm thick modified surface layer with α-Fe and NbC carbide major phases and negligible quantity of Fe₃C and Me₆C (Fe₃ W₃ C) carbides. The principle difference of the surface layer modified by electron beam processing from the unmodified volume of facing is morphology and dimensions inclusions of the second phases. In the facing modified layer inclusions have smaller dimensions and are located in form of thin interlayers along the grain boundaries. In the unmodified facing, basic morphological type of inclusions is particles of faceted shape located chaotically in grain volume. After electron beam processing wear resistance of the faced layer increases in more than 70  times in relation to wear resistance of Hardox  450 steel and friction coefficient decreases significantly (in ~3  times).

1. Mendez P.F., Barnes N., Bell K., Borle S.D., Gajapathi S.S., Guest  S.D., Izadia H., Gola A.K., Wood G. Welding processes for wear  resistant overlays. J. Manuf. Process. 2014, vol. 16, pp. 4–25.

2. Thorpe W.R., Chicco B. On the formation of duplex eutectic carbides in commercially important white irons. Mater. Sci. Eng. 1981,  vol. 51, pp. 11–19.

3. Randle V., Laird G. Microtexture Study of eutectic carbides in white  cast iron using electron backscatter diffraction. J. Mater. Sci. 1993,  vol. 28, pp. 4245–4249. 

4. Pearce  J.T.H.,  Elwell  D.W.L.  Duplex  nature  of  eutectic  carbides  in heat treated 30% chromium cast iron. J. Mater. Sci. Lett. 1986,  vol.  5, pp. 1063–1064.

5. Wiengmoon  A.,  Chairuangsri  T.,  Brown  A.,  Brydson  R.,  Ed-monds  D.V.,  Pearce  J.T.H.  Microstructural  and  crystallographi-cal study of carbides in 30 wt.% Cr cast irons. Acta Mater. 2005,  vol.  53, pp. 4143–4154.

6. Chen Xizhang, Shen Zheng, Chen Xing, Lei Yucheng, Huang Qunying. Corrosion behavior of CLAM steel weldment in flowing liquid  Pb-17Li at 480 °С. Fusion Engineering and Design. 2011, vol. 86,  no. 12, pp. 2943–2948.

7. Chen Xizhang, Fang Yuanyuan, Li Peng, Yu Zhenzhen, Wu Xiao-dong, Li Dongsheng. Microstructure, residual stress and mechanical properties of a high strength steel weld using low transformation temperature welding wires. Materials & Design. 2015, vol. 65,  pp.  1214–1221.

8. Konovalov  S.V.,  Kormyshev  V.E.,  Ivanov  Yu.F.,  Teresov  A.D.  Electron-beam processing of the hardened layer formed on Hardox  450 steel electric-wire welding system Fe-C-V-Cr-Nb-W. Letters on Materials. 2016, vol. 6, no. 4, pp. 350–354. (In Russ.)

9. Marquez-Herrera A., Fernandez-Munoz J.L., Zapata-Torres M. etc.  Fe2B  coating  on ASTM A-36  steel  surfaces  and  its  evaluation  of hardness  and  corrosion  resistance.  Surface and Coatings Technology. 2014, vol. 254, pp. 433–439.

10. Zahiri R., Sundaramoorthy R., Lysz P., Subramanian C. Hardfacing  using ferro-alloy powder mixtures by submerged arc welding. Surface and Coatings Technology. 2014, vol. 260, pp. 220–229.

11. Li R., Zhou Z., He D. et al. Microstructure and high temperature  corrosion behavior of wire-arc sprayed FeCrSiB coating. Journal of Thermal Spray Technology. 2015, vol. 24, no. 5, pp. 857–864.

12. Kapralov  E.V.,  Raikov  S.V.,  Budovskikh  E.A.,  Gromov  V.E.,  Vaschuk E.S., Ivanov Yu.F. Structural phase states and properties  of  coatings  welded  onto  steel  surfaces  using  powder.  Bulletin  of  the  Russian  academy  of  sciences.  Physics.  2014,  vol.  78,  no.  10,  pp.  1015–1021.

13. Gromov  V.E.,  Kapralov  E.V.,  Raikov  S.V.,  Ivanov  Yu.F.,  Bu-dovskikh  E.A.  Structure  and  properties  of  wear-resistant  coatings  deposited by electric arc method on steel with flux cored wires. Us-pekhi fiziki metallov. 2014, vol. 15, no. 4, pp. 213–234. (In Russ.).

14. Konovalov  S.V.,  Kormyshev  V.E.,  Gromov  V.E.,  Ivanov  Yu.F.,  Kapralov  E.V.,  Semin A.P.  Formation  features  of  structure-phase  states of Cr–Nb–C–V containing coatings on martensitic steel. Journal of Surface Investigation. 2016, vol. 10, no. 5, pp. 1119–1124.

15. Berns  H.,  Fischer  A.  Microstructure  of  Fe-Cr-C  Hardfacing  alloys with additions of Nb, Ti and B. Mater. Charact. 1997, vol. 39,  pp.  499–527.

16. Berns H., Fischer A. Abrasive wear resistance and microstructure of  Fe-Cr-C-B hard surfacing weld deposits. Wear. 1986, vol. 112 (2),  pp. 163–180.

17. Yüksel N., Şahin S. Wear behavior–hardness–microstructure relation of Fe-Cr-C and Fe-Cr-C-B based hardfacing alloys. Materials & Design. 2014, vol. 58, pp. 491–498.

18. Venkatesh B., Sriker K., Prabhakar V.S.V. Wear characteristics of  hardfacing  alloys:  state-of-the-art.  Procedia Materials Science.  2015, vol. 10, pp. 527–532.

19. Gualco A., Marini C., Svoboda H., Surian E. Wear resistance of Fe-based nanostructured hardfacing. Procedia Materials Science. 2015,  vol. 8, pp. 934–943.

20. Teker  T.,  Karatas  S.,  Osman Yilmaz  S.  Microstructure  and  wear  рrореrtiеs of AISI 1020 steel surface modified bу HARDOX 450  and FеВ powder mixture. Protection of Metals and Physical Chemistry of Surfaces. 2014, vol. 50, no. 1, pp. 94–103.

21. Malysh V.M., Soroka M.M. Elektricheskaya svarka [Electric welding]. Kiev: Tekhnіka, 1986, 111 p. (In Russ.).

22. Koval’ N.N., Ivanov Yu.F. Nanostructuring of the surface of cermet  and ceramic materials with pulsed electron beam treatment. Izv. vuz. Fizika. 2008, vol. 51, no. 5, pp. 60–70. (In Russ.).

23. Evolyutsiya struktury poverkhnostnogo sloya stali, podvergnutoi elektronno-ionno-plazmennym metodam obrabotki [Evolution  of structure of the surface layer of steel subjected to electron-ion-plasma processing]. Koval’ N.N., Ivanov Yu.F. eds. Tomsk: Izd-vo NTL,  2016, 304 p. (In Russ.).