Effect of near-surface residual stress and microstructure modification from machining on the fatigue endurance of a tool steel |
| |
Authors: | F Ghanem H Sidhom C Braham M E Fitzpatrick |
| |
Affiliation: | 1. Laboratoire de Mécanique, Matériaux et Procédés, LABSTI03 ESSTT 5 Avenue Taha Husse?n, B.P. 56, 1008, Bab Menara, Tunisia 2. Laboratoire de Microstructure et Mécanique des Matériaux, ENSAM, CNRS ESA 8006 151 bd de l’H?pital, 75013, Paris, France 3. Dept of Materials Engineering, The Open University, Walton Hall, MK7 6AA, Milton Keynes, United Kingdom
|
| |
Abstract: | This study concerns the effect of machining on the fatigue life of an EN X155CrMoV12 tool steel (SAE J438b), with regard to
the generation of near-surface residual stress and microstructural modification of the machined surface. Two possible methods
for machining tool steels were compared: electro-discharge machining (EDM), a high energy density process, and milling, a
more conventional cutting process. Particular attention was given to characterization of the surface roughness, microstructure,
and residual stress, using a combination of microstructural analysis, crack observation, scanning electron microscopy (SEM),
x-ray diffraction (XRD), and chemical composition changes by energy-dispersive x-ray. A decrease of around 35% in the fatigue
limit was observed for the EDM samples, compared with the milled samples. This was attributed to a tensile residual stress
state after EDM, combined with significant phase transformation and hydrogen embrittlement. The milled surfaces showed no
microstructural transformation or surface cracking and contained compressive residual stresses, all of which contributed to
an improved fatigue resistance. |
| |
Keywords: | electro-discharge machining fatigue surface integrity tool steel |
本文献已被 SpringerLink 等数据库收录! |
|