Project solutions: Low Pressure Carburizing

Low pressure carburizing (vacuum-carburizing) is gaining more and more importance in the markets due to the specific advantages of this process. A case study as follows shows this:

PROBLEM:

A cylindrical carburized and hardened prefabricated part shows damages (outbreaks) in a radial-proceeding small groove during loading of the part. A mechanical machining through grinding of the groove should be avoided.

Dimension ,approx.	30 mm outside diameter
	15 mm inside diameter
	30 mm height
	2-2 mm groove size radial in the centre

Demanded case depth	0,45-0,6 mm
Surface hardness	680 – 750 HV
Original heat treatment	gas carburizing with oil quench and tempering

SOLUTION:

Low pressure carburizing with acetylene generates an even case depth also in the internal side of the groove.With the application of high pressure quenching in a cold chamber (double chamber vacuum-furnace) with 10 bar nitrogen pressure a case depth of 0,5-0,6 mm also in the groove could be achieved.

Through the purely martensitic structure in the outer and inner surface of the socket the damages (outbreaks) could be avoided.

ADVANTAGES:

Minor inspection efforts of hardened parts as a result of the application of a reproducible low pressure carburizing process with acetylene gas
Reduced distortion of the load-jigs and consequently a longer lifetime of the jigs.
By using a modified load jigging design made from graphite a duplication of the parts per load and a considerable reduction of the heat treatment costs could be reached.

Author: Franz Bless