Build-up sequence
The specified sequence for multi-pass overlay welding to build up chemical composition and microstructure in a controlled manner. Prevents forging defects.
Physicochemical Mechanism of Action
The surfacing sequence determines the order in which different layers or alloys are deposited. This affects the chemical reaction between the metals and the resulting microstructure. Each layer is cooled under specific conditions, leading to different crystal forms.
Metallurgical Relevance & Welding Risks
An incorrect surfacing sequence can lead to chemical contamination and uneven stresses. This can result in cracks, fracture, or a lack of hardness development in the material. Especially with complex alloys, the correct order is crucial for a stable bond and desired microstructure.
Shop Practice & Action Guidelines
When surfacing, always follow the specific surfacing sequence for the material. Start with the lower layers and work upward. Ensure each layer is fully cooled before moving to the next. Use the prescribed temperature and time intervals for each layer. Regularly check the chemical composition and microstructure under magnification.