2022/09/14
Ti-6Al-4V Valve Bonnet Repair
Centre de métallurgie du Québec (CMQ), Fluoroseal Inc. (2018-2019)
Objectives
To repair cast parts while minimizing the impact on the final part’s properties.
background
The lost-wax casting process produces high-quality, high-value-added titanium parts. But rare defects can occur, even with a controlled process. This can result in the part’s rejection. An interesting alternative involves repairing the cast part rather than rejecting it to recover the metal. To achieve this, Fluorseal Inc. contacted the Centre de métallurgie du Québec (CMQ) to develop a repair process for a Ti-6Al-4V valve bonnet through a research project funded by the Natural Sciences and Engineering Research Council (NSERC).
The Challenge
Parts are typically repaired through welding. In certain cases, however, like those involving smaller parts, the energy transmitted through welding often becomes very high and can distort the part’s final geometry. Significant thermal stresses and the presence of heat-affected zones can also occur, increasing the risk of cracks in the alpha case over a longer range. This alpha case is always present because the heat treatment, along with the chemical and mechanical machining steps, are performed after the repair to avoid having to repeat these steps.