Welding processes used with Nickel-Aluminium Bronze components for service in the marine environment

镍铝青铜（NAB）因其良好的耐腐蚀性和抗生物污损性而广泛应用于与海水接触的船用部件，如外部固定件、螺旋桨和阀门。然而，在这种合金系统中产生有利的微观结构和机械性能的焊接工艺的开发是具有挑战性的，因此NAB中的焊缝比锻造材料更容易受到腐蚀和应力腐蚀开裂（SCC）的影响。这限制了NAB部件的可维护性，并需要昂贵的更换计划。在本项目中，将分析使用不同焊接工艺生产的NAB焊缝的结构特性和耐腐蚀性，并与钢焊缝进行沿着比较。NAB和钢焊缝将暴露于海洋环境，同时受到应力，并将监测腐蚀速率和生物污损生物群落。我们将通过光学和电子显微镜以及X射线衍射将这些信息与材料最终状态的分析联系起来，并将其与暴露后对焊缝进行的机械测试结果联系起来。这将使我们能够确定焊接工艺，产生有利的焊缝微观结构和晶体在这种材料中，以确定参与NAB焊缝退化的主导过程，并预测腐蚀对NAB焊缝的长期结构完整性的影响。在环境测试期间，我们还将调查海洋生物污损和腐蚀损害之间的联系。这将使我们能够开发更实用的、基于生物学的海洋焊缝腐蚀检测方法。这项工作与EPSRC的未来制造主题的材料工程（金属和合金）领域保持一致。我们将通过更深入地了解焊缝微观结构与腐蚀降解机制的关系，改进NAB部件制造和NAB部件修复的焊接方法。这将为船舶和海上结构的运营商以及英国海洋维护行业带来经济效益。这项工作的一个直接实际成果是为工业项目合作伙伴巴布科克国际集团在维修和大修（R&O）中使用的焊接工艺提供信息。它还将作为一种使能技术，用于NAB的增材制造（特别是线+弧增材制造），作为铸造的替代品，用于制造复杂形状的部件，目前正在由几家主要制造商开发。我们还旨在首次将微观结构与生物污垢联系起来，这将为NAB组件的腐蚀检测提供技术，有利于海上基础设施的安全性和可维护性

Nickel-Aluminium Bronze (NAB) is widely used in seawater-contacting marine components such as external fixings, propellers and valves due to its good corrosion resistance and biofouling resistance. However, the development of welding processes that produce a favourable microstructure and mechanical properties in this alloy system is challenging, so welds in NAB are much more vulnerable to corrosion and Stress Corrosion Cracking (SCC) than the wrought material. This limits the maintainability of NAB parts and makes expensive replacement programmes necessary.In this project, the structural properties and corrosion resistance of NAB welds produced using different welding processes will be analysed, along with those of steel welds for comparison. NAB and steel welds will be exposed to marine environments while being simultaneously stressed and both the corrosion rate and community of biofouling organisms will be monitored. We will link this information to analysis of the material's final state via optical and electron microscopy and X-ray diffraction, and to results from mechanical tests which will be performed on welds post-exposure. This will enable us to identify welding processes which produce favourable weld microstructure and crystallographic in this material, to determine the dominant processes involved in NAB weld degradation, and to predict the effects of corrosion on the long-term structural integrity of NAB welds. During the environmental tests, we will also investigate the link between marine biofouling and corrosion damage. This will allow us to develop more practical, biologically-based corrosion inspection methods for marine welds.This work aligns with the Materials Engineering (Metals & Alloys) area of EPSRC's Manufacturing the Future theme. We will improve welding methods both for manufacturing NAB components and for NAB component repair by developing a greater understanding of how weld microstructures relate to corrosion-based degradation mechanisms. This will lead to economic benefits to operators of vessels and offshore structures, and to the UK marine maintenance industry. A direct practical outcome of this work will be to inform the welding processes used in Repair and Overhaul (R&O) by the industrial project partner Babcock International Group. It will also act as an enabling technology for the use of additive manufacturing (esp. Wire + Arc Additive Manufacturing) of NAB as an alternative to casting for creating complex-shaped components, which is currently under development by several major manufacturers. We also aim to link microstructure to biofouling for the first time, which will enable provide techniques for corrosion detection in NAB components, benefitting the safety and maintainability of offshore infrastructure