Definition
A cast iron component made by pouring molten iron into a mold whose surface is cooled rapidly, typically by contact with metal chills. The fast cooling at the surface produces a hard, wear-resistant outer layer of white iron, while the slower-cooling interior remains tougher gray iron.
Plain English
Cast iron that has been cooled quickly on the outside during casting, giving it a hard, wear-resistant skin over a softer, tougher core.
Context Anchor
Seen in aircraft maintenance and engine-material discussions, especially where a part needs a hard surface because it rubs against another moving part.
Derivation
The term comes from the foundry practice of placing 'chills' — blocks of metal — against part of the mold to draw heat away rapidly. The chilled surface cools so fast that the carbon stays locked in a hard form rather than forming softer graphite.
Why Pilots Care
Chilled-iron surfaces resist scoring and wear far better than ordinary cast iron, extending the life of engine components that operate under high heat and pressure.
Intuition Check
Do not read chilled as meaning the iron is kept cold in the aircraft. Here, chilled means the iron was cooled quickly during manufacture to make part of it harder.
Example Sentence 1
The cam followers are made of chilled iron to resist wear from constant contact with the camshaft lobes.
Example Sentence 2
Mechanics checked the chilled iron surface for scoring before reinstalling the piston assembly.