The axial-torsional thermo-mechanical fatigue behavior for Ni-based superalloy GH4169 was investigated experimentally in the temperature interval from 360 °C to 650 °C. The experimental results showed that, in the same von Mises equivalent mechanical strain amplitude condition, the fatigue life can be seriously decreased when the axial mechanical strain and the temperature are in-phase, and the non-proportional loading of mechanical strains can result in the fatigue life to further decrease. The analysis results showed that the fatigue lives depend on the summation of fatigue, creep and oxidation damages. The interaction between dislocations and precipitations can induce the additional hardening under mechanical non-proportional loading, which can obviously increase the fatigue damage. The tensile mean stress and the non-proportional additional hardening can further increase the oxidation damage existed in all loading conditions, which result in the increase of inelastic strain at high temperature. Creep damage behavior on grain boundaries can be shown in the case of the high tensile stress and the high temperature acting simultaneously, and increased with shear stress at the same time. In addition, the tensile stress has an obvious effect on the nucleation of creep cavities contrasted to the shear stress at high temperature, and more creep damage can be caused by the non-proportional additional hardening.

Thermo-mechanical fatigue damage behavior for Ni-based superalloy under axial-torsional loading

Thermal-mechanical fatigue behavior and lifetime prediction of P92 steel with different phase angles

https://cronfa.swan.ac.uk/Record/cronfa31841/Download/0031841-01022017112114.pdf

The influence of phase angle, strain range and peak cycle temperature on the TMF crack initiation behaviour and damage mechanisms of the nickel-based superalloy, RR1000

A crack opening stress equation for in-phase and out-of-phase thermomechanical fatigue loading

Low cycle fatigue, creep and creep-fatigue interaction behavior of a TiAl alloy at high temperatures

This study considers the thermo-mechanical fatigue behavior of Mar-M247 LC under 0° (in-phase), +180° (out-of-phase), +90° (clockwise diamond) and −90° (counterclockwise diamond) phase shift between mechanical loading and temperature. Tests were carried out under total strain control with a temperature range of 100–850 °C and a heating and cooling rate of 5 K/s. Mechanical strain amplitudes were 0.3% to 0.6% with a strain ratio of R e =−1. Results show that for the strain amplitudes tested, lifetime depends significantly on the phase angle. For a given strain amplitude, lifetime increases in the sequence: in-phase

Influence of phase angle on lifetime, cyclic deformation and damage behavior of Mar-M247 LC under thermo-mechanical fatigue

Influence of dwell times on the thermomechanical fatigue behavior of a directionally solidified Ni-base superalloy

Lifetime, Cyclic Deformation and Damage Behaviour of MAR-M247 LC under Thermo-Mechanical Fatigue Loading with 0°, 180°, -90° and +90° Phase Shift between Strain and Temperature

An approach to lifetime prediction for a wrought Ni-base alloy under thermo-mechanical fatigue with various phase angles between temperature and mechanical strain

Thermomechanical fatigue (TMF) tests under in-phase (IP) and out-of-phase (OP) conditions with continuous and dwell time cycles were conducted on wrought Ni-base alloy NiCr22Co12Mo9 (comparable to Inconel Alloy 617). The temperature range was T = 100–850 °C. In dwell time tests, dwells of 5 min were introduced at Tmax = 850 °C. In continuous cycle tests, the material shows significant cyclic hardening, mainly because finely dispersed carbides of type M23C6 form inside the grains. Introducing dwell times leads to coarsening of these carbides, which reduces cyclic hardening leading to lower stress amplitudes and higher plastic strain amplitudes than in continuous cycle tests. Serrated yielding indicating dynamic strain ageing (DSA) effects occur prominently in dwell time tests and less pronounced in continuous cycle tests. The DSA effects appear to be closely related to formation and growth of the M23C6 carbides. IP and OP loading lead to comparable microstructural evolution and deformation behavior. Damage in form of cracks arises under IP loading predominantly intergranularly and under OP loading mainly transgranularly. Dwell times do not affect the dominant damage form. For both continuous cycle and dwell time tests, IP lifetime is shorter than OP lifetime indicating that intergranular cracks propagate faster than transgranular cracks. Introducing dwells unexpectedly increases the lifetime under IP loading, while OP lifetime is only slightly affected. The lifetime behavior is discussed based on the observed microstructural and damage evolution.

Stefan Guth

Papers

Influence of phase angle on lifetime, cyclic deformation and damage behavior of Mar-M247 LC under thermo-mechanical fatigue

Influence of dwell times on the thermomechanical fatigue behavior of a directionally solidified Ni-base superalloy

Lifetime, Cyclic Deformation and Damage Behaviour of MAR-M247 LC under Thermo-Mechanical Fatigue Loading with 0°, 180°, -90° and +90° Phase Shift between Strain and Temperature

An approach to lifetime prediction for a wrought Ni-base alloy under thermo-mechanical fatigue with various phase angles between temperature and mechanical strain

Influence of dwell times on microstructure, deformation and damage behavior of NiCr22Co12Mo9 under thermomechanical fatigue