Composition and structure of the diamond/low carbon steel transition zone obtained by contact heating in vacuum at Fe–C eutectic temperature

The study covers the structure, elemental and phase composition of products formed in the contact interaction between diamond and low-carbon steel in vacuum at the Fe–C eutectic melting temperature. Cylindrical tablets made of low carbon steel with a maximum carbon content of 0.1 wt.% and natural diamond crystals in the form of a pyramid (or truncated pyramid) were used as contact pairs. The flat bases of diamond crystals were mounted on the horizontal surface of steel tablets with the load applied to the top of diamond crystals. Contact samples were sintered in a vacuum furnace at a maximum heating temperature of ~1165 °C. After holding at this temperature for 5 minutes, the furnace was turned off and the temperature in its chamber decreased in free cooling mode. Sintered diamond/steel tablet samples were studied by optical and scanning electron microscopy, X-ray diffraction analysis and Raman spectroscopy. It was found that the Fe–C eutectic melt forms in the diamond/steel tablet contact zone, a thin layer of which, when solidified, welds a diamond crystal to the steel tablet under the temperature-time heating mode specified in the experiment. Their bonding strength is such that welded samples without separation can withstand intense cyclic loads during grinding and polishing when making longitudinal sections of samples necessary for metallographic studies. It was shown that the Fe–C eutectic alloy is a gray cast iron with a ferrite-perlite metal base and lamellar graphite inclusions. The microhardness of the solidified Fe–C eutectic was ~1714 MPa. The initial steel tablet with a ferrite-perlite structure was subjected to cementation during sintering in contact with diamond. The most intensive cementation occurred in the ~110 μm thick unmelted upper layer of the steel tablet, which adjoined the Fe–C eutectic during sintering. The microhardness of this layer was ~4945 MPa. As it deepens into the steel tablet there is a gradual transition of the perlite-cementite structure to a perlite one and further to the initial ferrite-perlite microstructure inwards the steel tablet. At the same time, the microhardness changes from ~ 4945 to 1570 MPa.

diamond, iron carbon alloys, eutectic, melt, microstructure, cast iron, ferrite, perlite, cementite

1. Semenov A.P., Pozdnyakov V.V., Lapshina V.A. Contact eutectic melting of diamond and graphite with iron triad metals. Doklady Akademii nauk SSSR. 1968. Vol. 181. No. 6. P. 1368—1371 (In Russ.).

2. Semenov A.P., Pozdnyakov V.V., Kraposhina L.B. Friction and contact interaction of graphite and diamond with metals and alloys. Мoscow: Nauka, 1974 (In Russ.).

3. Kolesnichenko G.A., Naidich Yu.V., Petrischev V.Ya., Sergeenkova V.M. Kinetics of contact melting in iron-carbon systems. Powder Metall. Met. Ceram. 1996. Vol. 35. No. 9—10. P. 529—532.

4. Pant U., Meena H., Shivagan D.D. Development and realization of iron-carbon eutectic fixed point at NPLI. MAPAN. J. Metrol. Soc. India. 2018. Vol. 33. P. 201—208.

5. Gurevich Yu.G. Theory of eutectic alloys and eutectic (contact) melting. Met. Sci. Heat Treat. 2010. Vol. 52. No. 7—8. P. 354—356.

6. Hsieh Y.-Z., Lin S.-T. Diamond tool bits with iron alloys as the binding matrices. Mater. Chem. Phys. 2001. Vol. 72. P. 121—125. DOI: 10.1016/S0254-0584(01)00419-9.

7. Tillmann W., Ferreira M., Steffen A., Rüster K., Mŏller J., Bieder S., Paulus M., Tolan M. Carbon reactivity of binder metals in a diamond-metal composites — characterization by scanning electron microscopy and X-ray diffraction. Diamond Relat. Mater. 2013. Vol. 38. P. 118—123.

8. Bukalov S.S., Mikhalitsin L.A., Zubavichus Ya.V., Leites L.A., Novikov Yu.N. Investigation of the structure of graphite and some other sp 2 carbon materials by means of micro-Raman spectroscopy and X-ray diffraction. Rossiiskii khimicheskii zhurnal. 2006. Vol. 50. P. 83—91 (In Russ.).

9. Korepanov V.I., Hamagachi H., Osawa E., Ermolenkov V., Lednev I.K., Etzold B., Levinson O., Zousman B., Eprella C.P., Chang H.-C. Carbon structure in nanodiamonds elucidated from Raman spectroscopy. Carbon. 2017. No. 121. P. 322—329.

10. Ferrari A.C., Robertson J. Raman spectroscopy of amorphous, nanostructured, diamond-like carbon, and nanodiamond. Philosoph. Trans. Royal Soc. London. Ser. A. 2004. Vol. 362. No. 1824. P. 2477—2512. DOI: 10.1098/rsta.2004.1452.

11. Mochalin V., Osswald S., Gogotsi Y. Contribution of functional groups to Raman specrum of nanodiamond powders. Chem. Mater. 2009. Vol. 21. No. 2. P. 273—279. DOI: 10.1021/cm802057q.

12. Sidorenko D.A., Zaitsev A.A., Kirichenko A.N., Levashov V.V., Kurbatkina V.V., Loginov P.A., Rupasov S.I., Andreev V.A. Interaction of diamond grains with nanosized alloying agents in metal-matrix composites as studied by Raman spectroscopy. Diamond Relat. Mater. 2013. Vol. 38. P. 59—62. DOI: 10.1016/j.diamond.2013.05.007.

13. Sonin V.M., Chepurov A.I., Zhimulev E.I., Chepurov A.A., Sobolev N.V. Surface graphitization of diamond in K2 CO3 melt at high pressure. Doklady Akademii nauk. 2013. Vol. 451. No. 5. P. 556—559 (In Russ.).

14. Sharin P.P., Yakovleva S.P., Gogolev V.E., Popov V.I. Structure and strength of transition area from natural diamond to chromium and cobalt carbide-forming metals under high-temperature interaction. Perspektivnye materialy. 2016. No. 7. P. 47—60 (In Russ.).

15. Gulyaev A.P. Metallovedenie. Мoscow: Metallurgiya, 1986 (In Russ.).

16. Fourlakidis V., Diaconu L.V., Diószegi A. Effect of carbon content on the ultimate tensile strength in gray cast iron. Mater. Sci. Forum. 2010. Vol. 649. P. 511—516. DOI: 10.4028/www.scientific.net/MSF.649.511.

17. Diószegi A., Fourlakidis V., Svensson I.L. Fracture mechanics of gray cast iron. Mater. Sci. Forum. 2010. Vol. 649. P. 517—522. DOI: 10.4028/www.scientific.net/MSF.649.517.

18. Bartocha D., Janerka K., Suchon J. Charge materials and technology of melt and structure of gray cast iron. J. Mater. Process. Technol. 2005. Vol. 162—163. P. 465—470. DOI: 10.1016/j.jmatprotec.2005.02.050.

19. Salawu E.Y., Ajaui O.O., Inegbenebor A., Akinlabi S., Akinlabi E. Influence of pulverized palm kernel and egg shell additives on the hardness, coefficient of friction and microstructure of grey cast iron material for advance applications. Results Eng. 2019. Vol. 3. P. 100025. DOI: 10.1016/j.rineng.2019.100025.

20. Oloyede O., Cochrane R.F., Mullis A.M. Effect of rapid solidification on the microstructure and microhardness of BS1452 grade 250 hypoeutectic grey cast iron. J. Alloys Compd. 2017. Vol. 707. P. 347—350. DOI: 10.1016/j.jallcom.2016.08.214.

21. Zalkin V.M., Kraposhin V.S. Structure of iron-carbon melts. About stability of cementite in melts. Met. Sci. Heat Treat. 2010. Vol. 52. No. 1—2. P. 3—6.

22. Gerasimova L.P., Guk Yu.P. Quality control of structural materials. Мoscow: Intermet Inzhiniring, 2010 (In Russ.).