LIFE 40 App B High temperature fatigue crack

LIFE 40 App. B High temperature fatigue crack propagation in nickel-based superalloys Erik Lundström & Jonas Saarimäki Linköping University

Outline • Background • Motivation • Hold times • Behaviour • Industry practice • Modelling approach • Lic. Thesis E. Lundström • Ongoing testing • New test geometry • Test rigs • Future work 2

Background • Deformation and damage mechanisms at high temperature and loads • The knowledge will help us to develop material models that can be used for FEM simulations • More efficient power generation by gas turbines 3

Background; cont. Area of interest = HPT discs F 110 -GE-100 4

Background; cont. Wanhill, R. Significance of dwell cracking for IN 718 turbine discs International Journal of Fatigue, 2002, 24, 545 - 555 5

Motivation • Inconel 718 is the most common superalloy in the gas turbine industry • The alloy is (among others) sensitive to embrittling elements • Sustained load – cruise or constant power output • Slow ramp-up of engine thrust • Slow shut-downs • Life prediction with time dependent loading • A lack of robust models • Increase in TRL • 6 Incorporation into the gas turbine industry life prediction programs

Hold times 7

Fracture modes • Transgranular and intergranular fracture 8

Modelling – industry standard • Current industry standard 9

Modelling – industry standard; cont. 10

Modelling – industry standard; cont. 11

Damaged zone • Differences from PD prediction and final fracture surface – ligaments in the crack wake which are electrically conductive • This is henceforth referred to as the damaged zone D Crack length by PD 12 Microstructural crack length = a+D

Modelling • Should be able to handle a wide spectrum of hold times • Should require few input parameters • Should be able to be modified to function over a wide range of conditions • Non-isothermal • Varying load ratios – presented at FATIGUE 2014 • Overloads / underloads – published in Phase 2 • Should be easy to use on a daily basis as an engineering tool for practical use 13

Modelling; cont. 14

Modelling; cont. • Calibration test for cheap and easy parameter determination • 1 test type for 8 model parameters • Time dep. parameters C 0 t , nt and Bt • Cyclic parameters Cc , nc , Ac and Bc • Maximum damaged zone length Dmax • Additional tests if scatter is to be handled 15

Modelling; cont. da/d. N da/dt C 0 t nt da/d. N Ac Bc Dmax Bt Load ΔK C c nc Kmax ΔK Time 16

Modelling; cont. 17

Statistics 18

Statistics - comparison Developed modelling approach 19 Industry standard

Lic. Presentation E. Lundström 20

Paper 1 – Overload behaviour 21

Paper 2 – Initial modelling 22

Paper 3 – Modelling and evaluation Paper 2 23

Paper 4 – Application to a flight spectrum Paper 3 24

A deeper insight in paper 4 - Application • Application to a flight spectrum • 25 TRL increase

Application; cont. 26

Application; cont. • 27 566 sequences (1468 s each) in total for the test • Test to model error of ~13%

Application; cont. 28

Paper 5 – Fracture surface investigation Paper 3 29

Modelling work - summary • A history dependent model based on LEFM • Cheap and easy calibration – 1 test needed (8 parameters) • Only need to keep track of 1 additional parameter (D) for handling history dependence • Easy to incorporate into existing life prediction codes • Validated through a wide range of load sequences and temperatures 30

Ongoing testing • Kb specimens • Wrought IN 718 • Cast IN 718 • Wrought EBW IN 718 • CT specimens (side-groove) 31 • Wrought IN 718 • Wrought Haynes 282

Ongoing testing; cont. • Test procedure CT specimens 32 • Inconel 718 • Haynes 282

Ongoing testing; cont. • Test rig • 33 Zwick

Ongoing testing; cont. • PD-modeling Validation and estimation of a+D Electrical potential V • Crack length a 34 Crack length a

TRL 6 TRL 4 Component and/or breadboard validation in laboratory environment 35 Future work System/subsystem model or prototype demonstration in a relevant environment ABAQUS

Deliverables – phase 2 • 3 papers in international journals • D. Gustafsson, E. Lundström (2013). High temperature fatigue crack growth behaviour of Inconel 718 under hold time and overload conditions, International Journal of Fatigue, Volume 48, pp. 178 -186. • D. Gustafsson, E. Lundström, K. Simonsson (2013). Modelling of high temperature fatigue crack growth in Inconel 718 under hold time conditions, International Journal of Fatigue, Volume 52, pp. 124 -130. • E. Lundström, K. Simonsson, D. Gustafsson, T. Månsson (2014). A load history dependent model for fatigue crack propagation in Inconel 718 under hold time conditions, Engineering Fracture Mechanics, Vol. 118, pp. 1730. 36

Deliverables – phase 2; cont. • 2 paper submitted for publication in an international journal 37 • E. Lundström, K. Simonsson (2014). Evaluation and prediction of crack length in a Ni-based superalloy for sustained loading, submitted. • J. Saarimäki, J. Moverare, R. Eriksson, S. Johansson (2014). Influence of overloads on dwell time fatigue crack growth in Inconel 718, submitted.

Deliverables – phase 2; cont. • 4 presentations at an international conference 38 • D. Gustafsson (2012). Overload considerations for holdtime fatigue crack growth in Inconel 718, International Conference on Fatigue Damage of Structural Materials IX. • E. Lundström and J. Saarimäki et al. (2013). High temperature hold time fatigue crack growth behaviour of Inconel 718, CEAS 2013. • H. Brodin, J. Saarimäki (2013). Mechanical properties of lattice truss structures made of a selective laser melted superalloy, ICF 13. • E. Lundström, K. Simonsson, T. Månsson, D. Gustafsson (2014). Modelling of fatigue crack growth in Inconel 718 under hold time conditions - application to a flight spectrum, Advanced Materials Research, Volumes. 891 -892, pp. 759 -764. FATIGUE 2014

Deliverables – phase 2; cont. • 1 Dissertation • D. Gustafsson (2013). High temperature fatigue crack propagation behaviour of Inconel 718 – Dissertation. • 1 Lic. Thesis. • E. Lundström (2014). Modelling of fatigue crack propagation in Inconel 718 under hold time conditions – Lic. Thesis. • 4 master thesis 39

Thank you for your attention! 40