Surface modification of austenitic steels by low‐temperature carburization

Abstract

a Austenitic stainless steels are characterized by good corrosion resistance in different environments, but their use is limited because of low hardness and poor wear resistance. Conventional thermochemical surface treatments for improving the mechanical strength of steels induce Cr carbide precipitation and thus are detrimental to corrosion resistance. A low-temperature (<470 C) plasma treatment has been developed to overcome this problem and to reduce simultaneously the costs and the time of process. This paper reports the results of a microstructural characterization performed on a series of AISI 316L steel samples treated by plasma-assisted low-temperature carburization in different conditions. Microhardness tests and X-ray diffraction indicated that the best results are achieved by employing a gas mixture with 2% of CH 4 in H 2 . XPS and AES were used to examine the chemical composition of the 20-mm-thick hardened layer. The results revealed that this layer is not homogeneous because a 2-mm-thick overlayer of graphitic nature forms on the surface. Furthermore, only the plasma treatment with 2% of CH 4 guarantees that the whole carbon remains in solid solution, whereas for higher CH 4 amounts in the gas mixture, carbide precipitation takes place.

High temperature tribological behavior and microstructural modifications of the low-temperature carburized AISI 316L austenitic stainless steel

“…This is in agreement with previous studies which showed that the LTC treatment induces the formation of a C-rich film with a strong graphitic nature, about 2 μm thick [28]. Nanoindentation measurements on this film showed a rather high elastic modulus (400 GPa at about 100 nm from the surface), indicating that the C-rich film probably also involves hard tetrahedral carbon, as in diamond-like amorphous carbon (DLC) coatings [29].…”

“…In fact, the elastic modulus of the C-rich layer, estimated by nanoindentation, steeply decreases already at 200 nm from the steel surface, as described in Refs. [28,29]. As already observed, these results confirm that LTC improves the dry sliding wear resistance of AISI 316L at room temperature, due to the significant hardness improvement, the ability of the carburised to resist surface plastic deformation and abrasion, as well as to limit adhesion between the mating surfaces [14].…”

Spectroscopy of carbon: from diamond to nitride films

“…The obtained results permitted to determine the dependency of sp 2 /sp 3 ratio on the deposition parameters: hydrogen flow rate and sample temperature for DLC and a‐CN x films, respectively. This approach seems to be a simple and reliable method for the characterization of bonding hybridization in different carbon‐based materials, for instance it was recently used for plasma‐carburized austenitic steel …”

Bimetal-gradient-layer surfacing of forging die manufacturing based on cast-steel substrate

“…to extend the service life of dies (Albertin et al 2001; Bagherifard et al 2013;Chen 2002). However, this method has many defects such as low material utilization, large amount of finishing, long production period, high cost and so on (Ciancaglioni et al 2012), which impedes the upgrading of products and lowers the competition ability.…”