Fundamentals of static crack growth in nickel-based superalloys after friction welding

镍基高温合金摩擦焊后静态裂纹扩展的基础

• 批准号: 2718829
• 金额: --
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2718829
• 关键词: Fundamentals; static; crack; growth; nickel

Turbine sections of jet engines undergo significant and varying stresses, as well as operational temperatures beyond 750 degrees Celsius, requiring the use of materials capable of maintaining their mechanical properties at high temperatures. Nickel based super-alloys are the current material of choice for aeroengine discs, owing to their high resistance to creep, fatigue, and static loading in the temperature regimes required. If friction welding can be used to join discs into a turbine assembly then weight savings can result. Inertia friction welding (IFW) processes are favoured to join these large components as they do not require shielding environments and welding parameters are easily repeatable and controllable. During this process one component is attached to a rotating flywheel while the other is held fixed. The flywheel is rotated to a predetermined angular velocity (and hence energy), and the two components brought into contact under high axial pressure. Rotational energy is converted to heat via friction at the interface, the softened materials are expelled radially from the work-piece as flash, and a bond is formed between two components. IFW produces large changes in microstructure. High heat generation and deformation in the weld region promote dynamic recrystallisation, as well as dissolution of gamma ' precipitates and their subsequent re-precipitation in a much finer distribution. Unfortunately, such microstructures are highly prone to intergranular cracking if given threshold conditions are exceeded. This cracking is so rapid in air that in could jeopardise the integrity of the aero-engine and cannot be allowed to occur. This project will study the fundamentals of this intergranular crack growth mechanism to define limits to ensure cracks cannot grow under in-service conditions.

喷气发动机的涡轮截面承受着巨大和不同的应力，以及摄氏750摄氏度以上的操作温度，需要使用能够在高温下维持其机械性能的材料。基于镍的超级合金是航空发动机盘的当前首选材料，因为它们对蠕变，疲劳和所需温度状态下的静态负载有高度的抗性。如果可以使用摩擦焊接将圆盘连接到涡轮组件中，则可以节省重量。惯性摩擦焊接（IFW）过程很喜欢加入这些大组件，因为它们不需要屏蔽环境，并且焊接参数易于重复且可控制。在此过程中，一个组件连接到旋转飞轮上，而另一个组件则固定。将飞轮旋转至预定的角速度（因此），并且在高轴向压力下将两个组件接触到了接触。旋转能通过界面处的摩擦转化为热量，易变的材料从工作型闪烁中径向排出，并在两个组件之间形成键。 IFW会产生微观结构的巨大变化。焊接区域的高热量产生和变形促进了动态重结晶，并溶解了伽马的沉淀及其随后的重新沉积，以更细腻的分布。不幸的是，如果超出给定阈值条件，那么此类微观结构很容易容易出现晶间裂纹。这种裂缝在空气上是如此迅速，以至于可能会危害航空引擎的完整性，并且不能允许发生。该项目将研究这种晶间裂纹生长机制的基本原理，以确定限制，以确保在服务中的条件下裂缝不能生长。