abstract
The constant search for alternative binders to commonly used in hard metal industry, i.e. cobalt, with improved features in terms of resistance to corrosion/oxidation, lower toxicity and lower cost is currently one of the strands of research in this area. For this, it is very important the prior knowledge of the behavior of the wettability of selected metals or metal alloys selected on the surface of the tungsten carbide (WC) because it is not found in the bibliography results relating to studies of wettability to high temperatures WC. It is known the difficulty in obtaining dense substrates-WC without binders and, to control this difficulty, it was used three types of substrates with the following strategy: (i) began the study with substrates of WC + 3.5% cobalt (Co), available on the market; (ii) coated these substrates of WC + 3.5% Co with a thin film of WC, by sputtering that were used with the expectation of creating a relatively stable WC interface during the tests and (iii) in a final phase of the work it was possible to obtain a WC substrate by hot-pressing, with ~ 100% of relative density, which was used in some tests. For the wettability tests the material (metallic binder) is placed on the substrate and is heated to temperatures in the order of the melting temperature of the material (sessile drop method). The temperature is keep constant until the melting of the material. The molten material forms a bubble on the surface of the substrate and the evolution of the contact angle recorded. The binders tested in the form of sheet metal were; copper, stainless steel AISI 316, iron, nickel and cobalt. From the metallic materials the one that shown less ability to wet the surface of the WC was the copper with contact angles values between 6 and 25°, depending on the type of substrate. By contrast steel, cobalt, iron and nickel have good wettability in the WC, with emphasis on the fact that stainless steel present contact angles of ~0°, comparable to those obtained with cobalt. Thesefindings were observed in the three substrates, however the presence of cobalt in the substrate decreases the contact angle in some cases and other metallic material spreading accelerates in the WC. In addition, with the exception of copper, cobalt and nickel, all the binders tested showed wettability reactive, with the formation of M6C and/or M4C.
subject category
MESTRADO EM GESTÃO (2º CICLO)
authors
Vera Liliana Ferreira e Silva
our authors
Vera Liliana Ferreira e Silva
MSc Studentsupervisors
Ana Maria de Oliveira Rocha Senos; Cristina Maria da Silva Fernandes
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