Shot peening and subsequent annealing - increase of the stability of residual stresses and fatigue limit shown at AISI 4140

摘要

Increases of residual stress stability and alternating bending strength of shot peened steel AISI 4140 (German grade: 42CrMo4) are obtained by successive annealing treatments. This is caused by static strain aging effects, which lead to pinning of the dislocations and stabilisation of the dislocation arrangement by carbon atoms and very small carbides. It will be shown that by well directed annealing of a quenched and tempered AISI 4140 after shot peening it is possible to maximize the positive effects of static strain aging, without causing extended thermal residual stress relaxation. The amount of yield stress increases caused by static strain aging is quantified using tensile tests and correlated to the increases in the alternating bending strength.