Journal of the Southern African Institute of Mining and Metallurgy
On-line version ISSN 2411-9717
KLENAM, D.E.P. et al. Mechanical behaviour of pack carburized AISI 316L austenitic stainless steel. J. S. Afr. Inst. Min. Metall. [online]. 2015, vol.115, n.12, pp. 1183-1191. ISSN 2411-9717. http://dx.doi.org/10.17159/2411-9717/2015/v115n12a6.
The effect of surface hardening by pack carburizing on the mechanical properties of AISI 316L steel was studied. Pack carburizing with 60 wt% BaCO3, 30 wt% activated carbon, and 10 wt% sodium chloride was carried out at 450, 550, 650, 700, and 750°C for 24 hours and the specimens were furnace-cooled. Tensile, impact, hardness, and fatigue tests were conducted, and SEM and was used to characterize the specimens. The ultimate tensile strength of the as-received steel was similar to specimens carburized at 450 and 550°C (approx. 650 MPa), but decreased from 638 to 603 MPa with further increase in carburizing temperature from 650 to 750°C. Hardness profiles of the specimens treated at 450°C and 550°C were similar to the as-received steel, at approximately 250 HV0.5. Typical case hardening profiles were obtained for specimens carburized at 650, 700, and 750°C. The number of cycles to failure (N) of the as-received specimens was close to 60 000, which was similar to those carburized from 450 to 650°C. Further increase in carburizing temperature decreased the cycles to failure to approximately 25 000 (700°C) and 7000 cycles (750°C). Crack initiation was mainly characterized by cleavage (mode I) for all tested carburized and as-received specimens. Specimens carburized at 450, 550, and 650°C also showed secondary cracking. The final rupture zone contained ductile fracture with dimples, and the specimens showed extensive plastic deformation.
Keywords : 316L austenitic stainless steel; mechanical behaviour; fractography; pack carburizing.