What Carburising Does to Titanium
Carburising introduces carbon into the surface of titanium at high temperature, where it combines with the metal to form titanium carbide, TiC. The carbide layer is extremely hard, far harder than the titanium substrate, and it changes the surface behaviour of the wire from soft and galling to hard and wear resistant. The core of the wire keeps its ductility, so the treated wire retains the strength and toughness of the base material.
The Carburising Process
Wire is carburised in a carbon-rich atmosphere or a carbonaceous pack at temperatures typically between 900 and 1000 degrees Celsius. Gas carburising uses hydrocarbon gases, pack carburising uses a solid carbon source, and laser carburising applies localized treatment with a scanned beam. The treatment time controls the case depth, and the process is followed by controlled cooling to limit distortion of the fine wire section.
Resulting Surface Properties
The titanium carbide layer reaches hardness values above 2000 HV, compared with roughly 200 to 350 HV for untreated CP titanium wire. The hard case improves resistance to abrasive wear, fretting and seizure in contact applications. The surface also shows lower friction against steel and other metals, which helps in wire guides, springs and fastening applications.
Surface hardness above 2000 HV on the carbide layer.
Improved abrasive and fretting wear resistance.
Reduced friction in sliding contact.
Ductile core retained for wire strength.
Limitations and Risks
The carbide case is thin and brittle, and heavy impact or sharp bending can crack it and expose the softer substrate. Carburising also introduces a risk of oxygen contamination and grain growth at the high process temperature, so fine wire needs careful control. Where deep, tough cases are required, diffusion treatments such as nitriding are evaluated alongside carburising.
Alternative Surface Treatments
Nitriding forms titanium nitride and is used for similar wear resistance with a different case structure. Thermal oxidation grows a thick oxide layer for moderate wear protection, and physical vapour deposition applies TiN coatings to finished parts. The choice depends on the wire diameter, the loading and the acceptable distortion of the final product.
Applications
Springs and wire forms in sliding mechanisms.
Wire guides and textile machine components.
Fastener wire for high-friction assemblies.
Medical instrument wire where wear particles must be minimized.
Frequently Asked Questions
Q: What does carburising do to titanium wire?
A: It forms a hard titanium carbide surface layer that raises hardness and wear resistance while the core keeps its ductility.
Q: At what temperature is titanium wire carburised?
A: Typically between 900 and 1000 degrees Celsius in a carbon-rich gas or pack atmosphere.
Q: How hard is the carbide layer?
A: The titanium carbide layer reaches hardness values above 2000 HV.
Q: What are the limits of carburising?
A: The case is thin and brittle, so impact and sharp bending can crack it, and high process temperature risks grain growth.
Q: What alternatives exist to carburising?
A: Nitriding, thermal oxidation and TiN coating are the main alternatives for titanium wear surfaces.
Q: Where is carburised titanium wire used?
A> In springs, wire guides, fastener wire and medical instruments where surface wear is the limiting factor.
