Effect of Heat Treatments for Electroless Deposited Ni-B and Ni-W-B Coatings on 7075 Al Alloy

摘要

Electroless Nickel ? Boron (Ni-B) coatings has a wide range of usage area including aerocraft and automotive applications as well as 7075 aluminum alloys. Electroless Ni-W-B deposits made a shift in wear resistance when compared to Ni-B coatings. In this study, an alkaline bath including sodium borohydride is used to reduce Nickel ions on the surface of 7075 aluminum alloy. Zincate treatment is the significant step before electroless deposition of Ni-B on aluminum alloys. During the deposition, pH and temperature values are set to appropriate range on the purpose of obtaining 20 μm deposit. With the aim of high wear resistance of the coated system both Ni-B or Ni-W-B coated substrates are heat treated with different temperatures. Effect of heat treatment on the hardness values of the specimens; bare 7075, Ni-B coated and Ni-W-B were obtained. Considering hardness values appropriate time and temperatures were selected. After heat treatments SEM micrographs and EDS anaylsis of the coated systems were investigated.