DOI: https://doi.org/10.15368/theses.2011.185
Available at: https://digitalcommons.calpoly.edu/theses/630
Date of Award
9-2011
Degree Name
MS in Engineering - Materials Engineering
Department/Program
Materials Engineering
Advisor
Dan Walsh
Abstract
Nickel super alloy Inconel 718 was tested and compared to Haynes 230 using Gleeble and Varestraint mechanical test methods. Hot cracking susceptibility was examined in either alloy using a sub-scale Varestraint test method at 5 augmented strain levels: 0.25%, 05.%, 1%, 2%, and 4%. Maximum crack length, total crack length, and number of cracks were measured for each strain level. Gleeble hot ductility on-heating and on-cooling tests were performed on both alloys. Inconel 718 was tested on-heating at target temperatures of 1600˚F, 2000˚F, 2100˚F, 2200˚F, and on cooling at 1600˚F, 1700˚F, 1800˚F, 1900˚F, and 2100˚F. Haynes 230 was tested on-heating at target temperatures of 2050 ˚F, 2200 ˚F, 2240 ˚F, 2330 ˚F, and on-cooling at 1800 ˚F, 1900 ˚F, 1990 ˚F, 2040 ˚F, 2090 ˚F, 2100 ˚F, 2140 ˚F, and 2190 ˚F. Ductility in Gleeble samples was measured in a reduction of surface area. A nil-strength temperature was established for either alloy. The nil-strength temperature was 2251˚F and 2411˚F, for Inconel 718 and Haynes 230, respectively. The nil ductility temperature <5% R/A) was 2188˚F for Inconel 718 and 2341˚F for Haynes 230. Ductility recovery temperature occurred at 1924˚F for Inconel 718 and 2147˚F for Haynes 230. The brittle temperature range was determined to be 326˚F for Inconel 718 and 228˚F for Haynes 230. Varestraint testing revealed that Inconel 718 had a lower threshold strain for crack initiation than Haynes 230 (0.5% vs 1%), and a higher number of cracks, as well as a larger maximum crack length, at every strain level. These results show a greater tendency for liquation cracks to form in Inconel 718 than in Haynes 230.