EXPLOITATION OF CANARIUM SCHWEINFURTHII CORE SHELLS AS CARBON SOURCE FOR CASE HARDENING OF STEELS

The objective of solid carburizing thermochemical treatment is to enrich with carbon the surface layer
of the substrate subjected to this treatment. This enrichment improves the mechanical (hardness),
tribological (wear) and microstructural properties of the treated substrate. The solid carburizer is a
carbon material that can release its carbon to diffuse into steel at high temperature, with or without a
catalyst. In this study, we have made solid carburizers from vegetable shells (bio-carburizers) from
Cameroon. These shells were first collected, crushed, washed, dried, ground and sieved at a grain
size of 300/500 μm and then carbonized at 450°C for periods of 10 to 60 minutes to obtain bio
carburizers. These bio-carburizers were then used for the case-hardening of cylindrical samples of
two different substrates (C35 and 42CrMo4 steel alloys) at 950°C for 3 hours. The samples were cut
radially and transversally, embedded in resin, polished and etched with nitric acid. The microstructural
analysis was done by optical microscopy. The measured Vickers hardness and the hardness profile
were obtained using a FALCON 500G204 durometer. Vickers hardness measurements show an
increase in hardness associated with the increase in carbon content in the surface layer. The hardness
profile allows to show a cemented thickness of up to 2 mm depending on the bio-cement used. The
microstructure observed by optical microscopy reveals a variation in the present phases depending
on the process for bio-carburizers production.