Definition
A case-hardening process in which low-carbon steel parts are packed inside a sealed metal box surrounded by a carbon-rich material such as charcoal, then heated to a high temperature for a sustained period. Carbon migrates from the packing material into the surface layer of the steel, producing a hard, wear-resistant outer case while the core remains tough and ductile.
Plain English
A way of hardening the outside of a steel part by burying it in carbon-rich material inside a sealed box and baking it. The surface soaks up carbon and becomes hard, while the inside stays softer and less brittle.
Context Anchor
Seen in aircraft maintenance and materials discussions when describing how some steel parts are surface-hardened for wear resistance.
Derivation
From 'pack' (to surround or enclose tightly) and 'carburize' (to add carbon to the surface of steel), itself from the Latin 'carbo' meaning coal or charcoal. The name simply describes the method: the part is packed in carbon-bearing material while carbon is added to its surface.
Why Pilots Care
Many engine and airframe parts rely on a hard surface over a tough core to resist wear without becoming brittle. Knowing how these parts are made helps a mechanic understand why surface damage, deep grinding, or improper repair can ruin the protective case and shorten part life.
Intuition Check
Pack carburizing is not related to a carburetor. Here, “carburizing” means adding carbon to the surface of steel during heat treatment.
Example Sentence 1
The camshaft lobes were hardened by pack carburizing to resist wear from the valve lifters.
Example Sentence 2
Pack carburizing was applied to the crankshaft to help it withstand repeated high loads in flight.