ABSTRACT The service lifespan of components used at higher temperatures in corrosive and abrasive
environments can be prolonged by high-temperature corrosion-resistant coatings. This study is
concerned with the microstructural characterization of some slowly cooled Nickel–based
hardfacing alloys investigated by differential thermal analysis (DTA), energy dispersive X – ray
analysis (EDXA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and
transmission electron microscopy (TEM). The alloys were prepared in high frequency induction
furnace under controlled atmosphere. Three major primary hard phases (Ni (α), M7C3, and the
π phase) were identified during slow cooling in DTA depending on the nominal compositions of
the alloys. Large undercoolings as well as intense solid state precipitations were observed in
alloys with iron additions. The precipitations formed the basis of the high hardness values and
strength of the alloys. It was also reported that the hardness values of the alloys increased as the
iron contents increased.
Cite this paper
J. Ajao, "Scanning Electron Microscopy of Some Slowly Cooled Nickel-Based Hardfacing Alloys Containing Iron Additions," Journal of Minerals and Materials Characterization and Engineering, Vol. 9 No. 2, 2010, pp. 133-145. doi: 10.4236/jmmce.2010.92012.
 Lugscheider, E., Knotek, O. and Klohn, K., 1978, “Development of Ni-Cr-Si base Filler Metals”, J. Weld. Res. Supp., Vol. 57 pp. 319 - 325.
Gonz′alez, R., Cadenas, M., Fern′andez, R., Cortizo, J. L. and Rodr′?guez, E., 2007, “Wear behaviour of flame sprayed NiCrBSi coating remelted by flame or by laser”, Wear Vol. 262 pp. 301–307.
Knotek, O. and Lugscheider, E., 1976, “Brazing Filler Metals based on Reacting Ni-Cr-B-Si Alloys”, Welding Research Supplement pp. 314 – 318.
Steffens, H.D., Ferrari, F., Sturlese, S.,and Pawlowski, L., 1992, “Fundamentals of Thermal Spraying Technology”, Mats. Eng., Vol. 3(2) pp. 183 - 190
Knotek, O., Reimann, H. and Lohage, P., 1981, “Reactions between Ni-Cr-B-Si matrixes and carbide additives in coating during fusion treatment”, Thin Solid Films Vol. 83 pp. 361 – 367.
Knotek, O., Lugscheider, E. and Wichert, W., 1978, “On the structure and properties of wear and corrosion resistant Ni-Cr-W-C-Si Alloys”, Thin Solid Films Vol. 53 pp. 303 – 312.
Rosso, M and Bennani, A., 1998, “Studies of new applications of Ni-based powders for hardfacing processes”, PM World Congress Thermal Spraying/Spray Forming, pp. 524-530.
Knotek, O., Lugscheider, E. and Reimann, H., 1975, “Structure of Ni-rich Ni-Cr-B-Si Coating Alloys”, J. Vac. Sci. Technol. Vol. 12(4) pp. 770 - 772.
Gonz′alez, R., Garc′?a, M. A., Pe?nuelas, I., Cadenas, Roc′?o, Fern′andez, Ma. Del., Hern′andez Battez, A., Felgueroso, D., 2007, “Microstructural study of NiCrBSi coatings obtained by different processes”, Wear Vol. 263 pp. 619–624.
Zhao, W-M., Wang, Y., Han, T., Wu K-Y. and Xue, J., 2005, “Corrosion mechanism of NiCrBSi coatings deposited by HVOF”, Surf. Coat. Technol. Vol. 190 pp. 293 – 298
Sidhu, T. S., Prakash, S. and Agrawal, R. D., 2006, “Hot corrosion and performance of Nickel - based coatings”, Current Science Vol. 90(1) pp. 41 – 47.
Otsubo, F., Era, H. and Kishitake, K., 2000, “Structure and phases in Nickel-base selffluxing alloy coating containing high chromium and boron”, J. Ther. Spray Technol. Vol. 9 pp. 107 – 113
Lee, C. H. and Min, K. O., 2000, “Effects of heat treatment on the microstructure and properties of HVOF – sprayed Ni – Cr – W – Mo – B alloy coatings”, Surf. Coat. Technol. Vol. 132 pp. 49 – 57
Wang, B. Q. and Luer, K., 1994, “The erosion – oxidation behaviour of HVOF Cr3C2–NiCr cermet coating”, Wear Vol. 174 pp. 177 – 185.
Lebaili, S., Durand-Charre, M. and Hamar-Thibault, S., 1988, “The Metallurgical Structure of as – solidified Ni-Cr-B-Si-C Hardfacing Alloys”, J. Mat. Sci. Vol. 23 pp. 3603 – 3611
Ajao, J. and Hamar-Thibault, S., 1988, “Influence of Additions on the Solidification Behaviour of Ni-B Alloys- Crystallography of the Ni - Ni3B eutectic”, J. of Mat. Sci. Vol. 23, pp. 1112-1125.
Gladyshevski, E. I. and Borusevich L. K., 1963, “Ternary system of Cr-Ni-Si”. Zh. Neorgan. Khim, Vol. 8 pp. 1915-1918
Adda, Y. and Philibert J. La diffusion dans les solides, Presses Universitaires de France, 1966.
Lebaili, S. and Hamar-Thibault, S., 1984, “Solid State Transformations During Cooling in the Ni-rich Portion of the Ni-Si system”, Z. Metallkde Vol. 75 pp. 764-770.
Ricks, R. A., Porter A. J. and Ecob R. C., 1983, “The growth of γ precipitates in nickelbased superalloys”. Acta Metall., Vol. 31, pp. 43-53.
Lebaili, S. and Hamar-Thibault, S., 1984, “Equilibres Liquide-solide dans le system Ni-B-Si dans la region riche en nickel”, Acta Metall. Vol. 35(3) pp. 701-710.