Porosity
Definition
Gas-filled voids in weld metal or castings, spherical or elongated (wormhole/piping), caused by dissolved gas evolving during solidification. Reduces cross-section and acts as a fatigue initiator.
- Cause
- Dissolved gas evolving during solidification
- Shapes
- Spherical, or elongated as wormhole/piping porosity
- Effect
- Reduces cross-section, acts as fatigue initiator
- Field
- Weld and casting failure analysis
Common questions
How is porosity detected before a failure occurs?+
Radiography and ultrasonic testing can reveal internal voids in a weld or casting before it enters service, while a failure investigation may find porosity directly at the fracture origin.
Why does porosity matter to a forensic failure analysis?+
A void reduces the load-bearing cross-section and concentrates stress at its edges, so it is a common origin point for the fatigue crack that ultimately caused the component to fail.
Related terms
- Hot Cracking
- Solidification cracking or liquation cracking that occurs at elevated temperature during or just after welding. Driven by liquid films of low-melting impurity...
- Hydrogen Cold Cracking (HCC)
- Delayed intergranular cracking in the heat-affected zone or weld metal, caused by atomic hydrogen absorbed during welding, susceptible martensite microstructure, and residual...
- Lack of Fusion (LOF)
- A planar weld defect where the weld metal fails to fuse to the base metal or to the adjacent weld pass. Essentially...
- Laminar Tearing
- Step-like fracture in the base plate beneath a restrained weld, propagating along planes of MnS inclusion stringers aligned with the rolling direction...
- Phased-Array Ultrasonic Testing (PAUT)
- Advanced ultrasonic inspection using a multi-element probe whose beam angle and focal depth are electronically controlled to scan a weld volume systematically....