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

镍铝青铜(NAB)具有良好的耐腐蚀性和抗生物污垢性能，被广泛应用于外固定器、螺旋桨、阀门等与海水接触的海洋部件中。然而，要在该合金系统中产生良好的组织和机械性能的焊接工艺的开发是具有挑战性的，因此NAB中的焊缝比变形材料更容易受到腐蚀和应力腐蚀开裂(SCC)。这限制了NAB部件的可维护性，并使昂贵的更换计划成为必要。在本项目中，将分析采用不同焊接工艺生产的NAB焊缝的结构性能和耐腐蚀性，并与钢焊缝进行比较。NAB和钢焊接将暴露在海洋环境中，同时受到压力，并将监测腐蚀率和生物污损生物群落。我们将把这些信息与通过光学、电子显微镜和X射线衍射对材料最终状态的分析联系起来，并与暴露后对焊缝进行的机械测试的结果联系起来。这将使我们能够确定在这种材料中产生良好焊接组织和结晶的焊接工艺，确定NAB焊缝退化所涉及的主要工艺，并预测腐蚀对NAB焊缝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垢和腐蚀损害之间的联系。这将使我们能够开发更实用的、基于生物的海洋焊接腐蚀检测方法。这项工作与EPSRC的制造未来主题的材料工程(金属和合金)领域保持一致。我们将改进制造NAB部件和修复NAB部件的焊接方法，方法是更好地了解焊接微结构与基于腐蚀的退化机制的关系。这将为船舶和海上结构的运营商以及英国的海洋维修业带来经济利益。这项工作的一个直接实际成果将是向工业项目合作伙伴Babcock International Group在维修和大修(R&O)中使用的焊接工艺提供信息。它还将成为使用添加剂制造的一种使能技术(特别是焊丝+弧光添加剂制造)，作为铸造生产复杂形状部件的替代方案，目前正由几家主要制造商开发。我们还首次将微观结构与生物污垢联系起来，这将使我们能够提供NAB组件中的腐蚀检测技术，从而有利于近海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