Stable process control is crucial in industrial heat treatment
– especially when using vacuum furnaces – in order to achieve uniform and reproducible material properties on the treated workpieces. Industries such as the aerospace and automotive industries produce sophisticated components for which a uniform surface hardness across the entire component is essential. To meet these requirements, Graphite Materials has developed special CFC charging racks.
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Gears and shafts are key components in drive and transmission systems – whether in vehicle construction, industrial plants or aviation applications. They transmit torque, must mesh precisely and withstand extreme mechanical stresses. Precisely coordinated
heat treatment – is crucial for their durability and functional reliability. To make them more resistant, Low Pressure Carburizing (LPC) uses a C-carrier gas – typically a carbon-containing gas such as acetylene, methane or propane. At high temperatures, the gas decomposes and the released carbon diffuses into the edge zone of the workpiece. This form of heat treatment – also known as case hardening or surface carburizing – specifically improves the surface properties without impairing the toughness of the core. Low-pressure carburizing, a modern variant of case hardening, specifically improves the hardness and wear resistance of the surface layer while maintaining the toughness and ductility of the core.
Industry:
Aerospace / automotive Industry
Procedure:
Vacuum heat treatment
Solution:
CFC fixtures with channel structure for optimised gas distribution at contact points
Services:
Result:
Uniform hardness values across the entire component – including on contact surfaces
A central problem area in low-pressure carburising lies in the support of the workpieces on charging racks: Contact surfaces between the component and the carrier are difficult to access for process gases, which can lead to uneven hardening depths and so-called soft spots. These inhomogeneous hardness distributions increase the risk of component distortion and, in the worst case, lead to the rejection of finished parts – with correspondingly high economic consequences.
A customer from the heat treatment industry approached Graphite Materials with the aim of developing a solution to prevent the soft spots described above. The requirements were:
The solution to this challenge lies in the details of the charging technology: a CFC workpiece carrier with a special surface contour is used here. The carrier material consists of carbon fibre-reinforced carbon ( CFC ), a particularly temperature and dimensionally stable material that is particularly suitable for repeated use in high-temperature processes.
The carrier plate is provided with a pyramid pattern patented by Graphite Materials. This surface contouring enables the improved flow of C-carrier gases even to those component areas that are in direct contact with the carrier plate. In this way, the required gas homogeneity can be maintained right up to the contact surfaces during low-pressure carburising.
The patented design of the surface structure ensures that the process gas also reaches the previously critical contact surfaces between the component and the carrier plate. As a result, the contact surfaces of the components are evenly enriched with carbon, regardless of their position on the CFC workpiece carrier. The process control remains stable and reproducible, so that the required hardening depth and surface quality is reliably achieved in all relevant areas of the components.
The implemented solution shows significant improvements in several areas:
Any questions?
Graphite Materials GmbH
Rothenburger Straße 76
90522 Oberasbach
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