Efeito do tratamento térmico em um revestimento de NiP depositado sobre uma superfície retificada de aço SAE/AISI 4140

Abstract

The protection of equipments exposed to aggressive environments regarding corrosion and abrasive wear is becoming something more and more attractive to many industries. The NiP coating offers protection with interesting properties to many diverse situations, since it have high resistance to abrasive wear and corrosion. The improvement of this coating makes it increasingly pursued by the industry as a solution in parts protection. The present work compared and evaluated the protection against abrasive wear and corrosion in NiP and NiP/Al2O3 coatings deposited on a grinded surface of SAE/AISI 4140 steel, heat trated at diferente temperatures. Through the use of adhesion test under the DIN VDI 3198 norm, corrosion test using cyclic voltammetry and linear polarization techniques, and wear test using free sphere microabrasion technic, it was possible to evaluate the best heat treatment conditions where the proposed coatings showed the best resistance results. It was found that, concerning abrasive wear resistance, the best heat treatment temperature for the NiP coating is 400ºC due to the high value of hardness and the acceptable level of adhesion achieved by the coating when heat treated in this temperature being responsible for the low value of worn volume obtained. In relation to corrosion resistance, the best heat treatment temperature for the NiP coating is 610ºC due to the generation of interdiffusion and oxid layers, what makes difficult the corrosion process. Furthermore, it was possible to verify that the inclusion of Al2O3 in the coating matrix is extremely bad to the deposition quality under the used parameters.