Creep deformation is one of the life time limiting reasons for gas turbine
parts that are subjected to stresses at elevated temperatures. In this
study, creep rupture behavior of uncoated and platinum-aluminide coated
Rene?80 has been determined at 760?C/657 MPa, 871?C/343 MPa and 982?C/190
Mpa in air. For this purpose, an initial layer of platinum with a thickness
of 6?m was applied on the creep specimens. Subsequently, the aluminizing
were formed in the conventional pack cementation method via the Low
Temperature-High Activity (LTHA) and High Temperature-Low Activity (HTLA)
processes. Results of creep-rupture tests showed a decrease in resistance to
creep rupture of coated specimen, compared to the uncoated ones. The
reductions in rupture lives in LTHA and HTLA methods at 760?C/657 MPa,
871?C/343 MPa and 982?C/190 MPa were almost (26% and 41.8%), (27.6% and
38.5%) and (22.4% and 40.3%), respectively as compared to the uncoated ones.
However, the HTLA aluminizing method showed an intense reduction in creep
life. Results of fractographic studies on coated and uncoated specimens
indicated a combination of ductile and brittle failure mechanisms for all
samples. Although, the base failure mode in substrate was grain boundary
voids, cracks initiated from coating at 760?C/657MPa and 871?C/343. No
cracking in the coating was observed at 982?C/190MPa.
Relation between Creep Rupture Properties and Microstructures of AISI 321 Stainless Steel Forgings
