Porosity is a phenomenon that occurs in materials, especially castings, as they change state from liquid to solid during the manufacturing process. Impregnation is a cost effective, permanent solution to the problems that may be encountered as a result of such porosity.
Holes or defects may be created that are too small to be seen by the naked eye and if these are permeated by gas or fluid, significant and costly quality problems can arise, even leading to the failure of the component in service through leaks or surface defects.
Vacuum impregnation is the permanent solution to this problem,filling any void with a stable yet flexible material that is resistant to attack from heat, oils or chemicals. The process is sub-surface and can be performed on raw materials or the finished machine part, causing no dimensional change or contamination to the component.
Impregnation Services
Porosity can be found in many materials but is particularly prevalent in aluminium dies castings, where three main types may be identified:
- FLOW POROSITY, resulting in surface or internal defects caused by poor pressure conditions in the process.
- GAS POROSITY, usually internal, caused by trapped gases of various kinds in the die.
- SHRINK POROSITY, the most common and most difficult to control, caused by the change in volume as the metal changes state from liquid to solid.
No matter how much care is taken in producing aluminium castings, porosity can still occur, usually during the change from a liquid state to a solid during the casting process. Impregnation is a cost effective, permanent solution to the problems that porosity may cause in some applications.
Melbourne Gravity can offer through its subsidiary IMPREGNATION SERVICES, the solution and seal most porosity problems, both gas and shrinkage. This service is provided for both castings produced by Melbourne Gravity and any other castings regardless of their origin.
The process uses ULTRASEAL PC504/66 Methacrylate Sealant, which once set can operate at temperatures between -50 to 200 degrees Celsius.