Print Email Facebook Twitter A Comparative Study of Thermo-Mechanical Fatigue Performance of Different Grades of SiMo Nodular Cast Iron Title A Comparative Study of Thermo-Mechanical Fatigue Performance of Different Grades of SiMo Nodular Cast Iron Author SHANKAR, SID (TU Delft Mechanical, Maritime and Materials Engineering) Contributor Kestens, L.A.I. (mentor) Petrov, R.H. (graduation committee) Riemslag, A.C. (graduation committee) Kalra, Aakarshit (graduation committee) Degree granting institution Delft University of Technology Programme Materials Science and Engineering Date 2018-09-27 Abstract This thesis is a comparative study of the Thermo-Mechanical Fatigue (TMF) performance of different grades of SiMo nodular cast iron for heavy-duty diesel engine exhaust gas manifold applications. The TMF performance of the current SiMo variant used to manufacture exhaust manifolds - SiMo 5.10 (C-3.25Si-4.45Mo-0.76), is compared with that of the variants SiMo 4.05 (C-3.22Si-4.66Mo-0.56) and SiMoNi (C-3.3Si-4.5Mo-1Ni-1.3) by performing three out-of-phase (OP) TMF test series under partial constraint conditions. A benchmark TMF test series in the temperature range: 50 ˚C to 550 ˚C with a hold time of 30 s at 550 ˚C showed that SiMo 5.10 had relatively better performance due to development of lower mechanical crack driving forces compared to other variants. However, a long holding time of 600 s at 550 ˚C saw a larger decrease of average TMF lifetimes for SiMo 5.10 than that of SiMo 4.05 despite similar crack driving forces. An investigation of the stress relaxation during TMF of the two variants showed that the SiMo 4.05 performs better during long hold time due to better stress relaxation properties. The SiMoNi variant which is very brittle at low temperatures was found to fail by a fracture by overloading mechanism taking over quite early in the fatigue cycle; which is confirmed by examination of the fracture surfaces and numerical estimations. This also explained the low lifetimes and scatter in previously performed TMF tests under total constraint conditions. The TMF test series performed in the temperature range: 150 ˚C to 550 ˚C with a hold time of 30 s at 550 ˚C found that a heat-treatment seemed to reduce the TMF performance of the SiMo 5.10 variant. Metallographic investigations and hardness measurements of as-cast and heat-treated materials revealed that the distribution of the Mo-rich phase from the grain boundary regions into the matrix due to an annealing heat-treatment seemed to affect the TMF performance. Subject Thermo-Mechanical FatigueSiMo Nodular Cast ironFracture MechanicsExhaust Manifold To reference this document use: http://resolver.tudelft.nl/uuid:ab148549-c757-4b1d-a6f1-c59bc02df638 Embargo date 2022-09-27 Part of collection Student theses Document type master thesis Rights © 2018 SID SHANKAR Files PDF Siddharth_Shankar_Master_ ... grades.pdf 3.18 MB Close viewer /islandora/object/uuid:ab148549-c757-4b1d-a6f1-c59bc02df638/datastream/OBJ/view