Improvement of wear resistance by thermal spraying on surface layers prepared by plasma transferred arc welding on gray cast iron components

摘要

Bronze is surface welded by plasma transferred arc welding on gray cast iron components to enhance their corrosion resistance. Potentiodynamic polarization measurements as well as immersion in artificial seawater are used to investigate the corrosion mechanisms. While gray cast iron corrodes actively, the bronze surface layer forms a passive layer and corrosion is reduced. The wear resistance of the produced bronze surface layers under complex loading, e.g. cavitation and erosion is poor. Thus, hard thermal spray coatings of aluminum oxide, chromium oxide and WC-particle enhanced cobalt based powders are thermally sprayed on top of the bronze surface layers to enhance the wear resistance. In contrast to the bronze surface layer, the thermal spray coatings have interconnected porosities, i.e. that corrosive media can penetrate these coatings. Therefore, it is necessary to investigate whether the corrosion resistance of the underlying bronze surface layer is maintained. The corrosion properties of these multilayer-systems are investigated similar to the gray cast iron and bronze surface layer. Investigations of the behavior under erosive-corrosive load showed promising results for the concept of functionally separating the wear protection and corrosion protection of gray cast iron by a thermal spray coating on top of a bronze surface layer.