Avaliação da resistência ao desgaste microabrasivo dos metais duros WC-Ni-Mo2C, WC-Ni-Al e WC-Ni-Cr3C2

Abstract

The Brazilian industrial sector has suffered great losses due to abrasive wear, since this type of wear is one of the main factors for machinery and equipment breakdown. In order to mitigate this problem, cemented carbides have been increasingly used in applications involving abrasive wear. Conventional carbide is a cobalt and WC material, which has certain disadvantages, one of the main ones being the low corrosion resistance due to the cobalt binder. Thus, research conducted by Penrice (1987), Almond and Roebuck (1988), Tracey (1992), point to nickel as more promising and lower cost. The nickel binder is a less expensive material, has superior performance regarding oxidation and corrosion in acidic and aqueous environments compared to cobalt, but loses in wear resistance by presenting lower hardness. Thus, the combination with auxiliary carbides arises to increase the hardness of the composite. An important factor regarding the manufacture of carbide, which is by powder metallurgy, is the fact, that the composite produced presents a certain level of porosity. This porosity is responsible for performance losses to abrasive wear. Thus a good final product should have a low level of porosity. The evaluation of abrasive wear consisteddistância in subjecting three specimens with distinct nickel binder and auxiliary carbides and one with cobalt binder to a microabrasive test, monitoring the wear evolution, the acting micromechanisms, and later comparing the results between both specimens. Scanning electron microscopy was used to evaluate the worn surface and study the actuating wear mechanisms, where it was possible to observe the action of the two-body and three-body mechanisms. In the wear test, compared to the samples with the conventional carbide 90WC-10Co, sample 90WC-9.5Ni-0.5Al performed better, sample 90WC-8Ni-2Mo2C performed similar wear behavior, and finally sample 90WC-8Ni-2Cr3C2 showed the lowest performance. Given the results it is possible to say that cemented carbides produced with nickel and added carbides to improve performance are efficient since they maintain quality in manufacturing in relation to porosity and thus can be an excellent option to replace conventional cemented carbide.