Investigation on a new durable surface treatment for titanium alloys to improve the adhesion properties for aerospace applications

摘要

In aerospace industry new design concepts offering weight savings are high in demand.Due to the increasing amount of composite materials also the percentage of titanium materials rises to ensure galvanic compatibility.However,it is known in aerospace industry that titanium materials exhibit issues in regard to long-term stable and durable adhesion.This paper evaluates presents a new anodizing treatment(N4-process)which leads to long-term stable and durable paint adhesion on titanium materials.Within this study a new alkaline anodizing process(N4-Process)is used as a pre-treatment of the titanium alloy Ti6AI4V.For reference,an acidic etching process(HF/HN03 etching solution)and a second anodizing procedure(Sulphuric Acid Anodizing,SAA)are employed to evaluate the nanostructure and adhesion properties obtained by the N4-Process.The influence of nano-and microstructure on adhesion properties was investigated using cross hatch test as well as a pull-of test.Additionally,the morphology of the titanium oxide layers and the fracture surfaces of the titanium oxide layers were analyzed via scanning electron microscopy(SEM)and transmission electron microscopy(TEM).Moreover the durability of the oxide layers after anodizing was investigated in hot-wet conditions.One aim of the work is to establish a better understanding of the long term stability of paints on titanium substrates.Within this work the correlation between the stability of the oxide layer and the paint adhesion were studied.