Effect of local stress on the heat-checking morphology in high temperature tool steels under thermal fatigue: Transition from multi-axiality to uniaxiality

Abstract

To cite this version:Farid Medjedoub, Sabine Le Roux, Gilles Dour, Farhad Rezai-Aria. Effect of local stress on the heat-checking morphology in high temperature tool steels under thermal fatigue: Transition from multi-axiality to uniaxiality. Mechanics of Materials, Elsevier, 2014, 69 (1), p. a b s t r a c tThermal fatigue experiments are performed on a high temperature tool steel X38CrMoV5 (AISI H11), under various maximum temperatures and heating rates. A microscopic interconnected crack pattern (named ''heat-checking'') forms on the oxidised surface of the laboratory tubular specimen. A gradual transition is observed, from a ''cell-type'' cracking at the centre of the specimen to a ''parallel cracking'' at its extremities. This variation of the morphology is well demonstrated by geometrical and topological characteristics of the crack network (micro-crack orientations, cell shape and node density), which change along the longitudinal axis of the specimen. The thermo-elasto-plastic loading of the specimen is estimated by Finite Element Calculations using ABAQUS™. Whatever the thermal fatigue conditions, a linear correlation can be established between the longitudinal and hoop stress amplitude ratio Dr zz /Dr hh and the hoop and longitudinal inter-crack spacing ratio d hh /d zz . It is shown that a stress amplitude ratio close to 1 results in a multi-axial heat-checking, while a uni-axial cracking is generated when Dr zz /Dr hh is close to or below 0.6. This means that the morphology of the heat-checking pattern (cell or parallel type) can be used as an indicator for the local stress ratio of the thermal fatigue specimen or industrial real tools. Fig. 1. (a) Geometry of the TF specimen; (b) instrumented dummy specimen with 28 K-thermocouples spot-welded on the external surface and eight thermocouples brazed in depth.

Effect of aluminizing and oxidation on the thermal fatigue damage of hot work tool steels for high pressure die casting applications

“…1d) or uniaxial in geometrical singularities (Fig. 1e) [19]. The formation of a macroscopic heat-checking network on the mould significantly reduces the quality of produced parts, requiring subsequent finishing operations and the scrapping of the die when the defects are too large.…”

Numerical simulation of thermal fatigue behavior in a cracked disc of AISI H-11 tool steel

“…Some of the setups include a disc heated by induction on the periphery [1][2][3][4][5][6][7][8][9][10][11][12], triangular blade heated by induction [13], electrical heating of tube followed by water splashing to induce thermal shock [14][15][16][17][18], hot dipping of cylinders in molten aluminum [19,20], laser heating [21,22], focused halogen lamps heating [23,24], convection/combustion heating [25,26], furnace heating with water quenching [27,28] and actual dies [29,30]. Out of these experimental setups most researchers have worked on the heated disc problem.…”

Thermal Fatigue Model of Aluminium Alloy Die Casting H-13 Dies under Thermo-Mechanical Cycle

“…With limited cases of thermal fatigue, it is assumed that whole thermal strain transformed into mechanical strain. This case is the basis of most thermal fatigue theories which indicate that fixed bar exists at ends between two fixed plates; thus, the bar length must be kept constant [19][20][21][22][23].…”