Method for low-pressure carburizing of a workpiece comprising steel

A method for low-pressure carburizing of a workpiece comprising steel, said steel comprising, in weight percent:

• from 0.10% to 0.20% in carbon (C),
• from 0.1% to 20% in cobalt (Co),
• from 2% to 15% in nickel (Ni), and
• from 1% to 10% in chromium (Cr),
• the method comprising:
• placing said workpiece in a carburizing enclosure, and
• implementing between 1 to 30 consecutive carburizing cycles, each carburizing cycle comprising:
• injecting a carburizing gas into the carburizing enclosure, so as to enrich a surface of the workpiece with carbon and to increase a surface rate of carbon of the workpiece up to a predetermined higher surface rate, the carburizing gas being injected into the enclosure at a first flow rate of between 1000 Nl/h and 3000 Nl/h, a temperature of the carburizing enclosure being between 950° C. and 1050° C., and injecting the carburizing gas for a first period of time of between 30 and 250 s, and
• injecting a neutral gas into the carburizing enclosure, so as to diffuse carbon from the surface to an interior of the workpiece, and to decrease the surface rate of carbon of the workpiece to a predetermined lower surface rate, wherein injecting the neutral gas comprises a first phase of injecting the neutral gas, at a second flow rate of between 1000 and 10000 Nl/h, and for a second period of time of between 5 and 60 s, followed by a second phase of injecting the neutral gas, at a third flow rate of between 500 Nl/h and 3000 Nl/h, and for a third period of time of between 10 and 2000 s.