2/26/2019 | 1 MINUTE READ

Understanding Porosity to Prevent Defective Castings

Facebook Share Icon LinkedIn Share Icon Twitter Share Icon Share by EMail icon Print Icon

Porosity can affect the structural integrity and functionality of castings, but performing vacuum impregnation at the right point in the part production process can prevent these issues.


Facebook Share Icon LinkedIn Share Icon Twitter Share Icon Share by EMail icon Print Icon

Porosity is a naturally occurring phenomenon that is found in most materials, but it can affect the structural integrity and functionality of metal castings. Vacuum impregnation is an effective way to seal porosity in castings, but companies need to choose whether to perform this operation before or after machining the casting. The article “When to Vacuum Impregnate Castings” explains how companies can make the best decision.

Understanding the types of porosity that occur in castings can help companies decide when to vacuum impregnate castings. In metal castings, porosity is considered to be any void in the casting. Porosity comes in three types: blind, which is open in one surface; through, which is open in two surfaces; and fully enclosed, with no passages to the surface. Through and blind porosity pose immediate problems. Through porosity creates leak paths that enable gas and liquids to escape, while blind porosity can cause internal corrosion and defects if cleaning solutions leech out of the voids after surface finishing.

Featured Content

CNC Machine Shop Reaps Benefits of Hiring an IT Person
CAD/CAM Software Helps Shops Shift to Coronavirus Work

Machining can affect the porosity of a casting. Blind porosity can be opened on the opposite side to create through porosity, while enclosed porosity can be exposed and become either blind or through. Therefore, the best way to ensure leak-free castings is to perform vacuum impregnation on all of them after final machining. However, performing leak tests on individual parts and vacuum impregnating ones that fail is a good alternative. Manufacturers can also increase the amount of material removed during cubing to maximize porosity exposure and perform vacuum impregnation after. This reduces the opportunity to open porosity during final machining.

To learn more, read “When to Vacuum Impregnate Castings.”   



  • April 2019 Product Spotlight: Cleaning and Deburring

    This month’s Modern Equipment Review Spotlight focuses on equipment used to remove imperfections from and clean finished workpieces.

  • Eco-Friendly Cleaning System Reduces Costs

    In addition to helping meet cleanliness specifications, Dürr Ecoclean’s Compact 80C parts washer has reduced energy, waste removal and labor costs at this precision parts manufacturer.

  • For Laser Shops: Oxidation Retaliation

    In an effort to prevent field paint failures, OEMs can no longer accept parts with the oxide buildup. A mechanical means of removal such as hand buffing or grit blasting is commonly practiced. However, these time-consuming and often labor-intensive processes can represent a substantial expense, and they can also introduce inconsistencies.

Related Topics