Abstract
The effect of defined preloading in the tensile and compressive regime on the near surface (residual) stress distributions, which result from laser surface hardening, is systematically studied in-situ, i.e. under the applied preload and after unloading. Samples made of steel grade AISI 4140 are defined surface hardened by means of a high-power diode laser (HPDL) system during uniaxial compressive elastic loading at-300 MPa as well as during uniaxial elastic tensile loading at 300 MPa using a custom designed 4-point-bending device, which can be mounted on an X-ray diffractometer. The results of X-ray stress analysis were compared to data derived for a sample state unaffected by any preload. Without external loading compressive residual stresses are induced inside the process zone that are balanced by tensile residual stresses outside this zone. The investigations show that external loading in the tensile and compressive regime has a strong impact on the resulting lateral residual stress distribution in loading direction. The results further indicate that undesirable tensile residual stresses outside the process zone can even be suppressed by using a defined appropriate preloading in the tensile regime.
Highlights
Thermal as well as thermo-mechanical processes exhibit an enormous technical and economic importance for surface optimization for improvement of the surface integrity, since most degradation processes like e.g. corrosion or crack initiation have their origin at the very surface of technical components
This local transformation is accompanied by characteristic residual stress distributions with compressive residual stresses directly in the process zone, which are balanced by tensile residual stresses outside of the laser processed material volume [1,2,3]
Stationary laser surface hardening on quenched and tempered steel type AISI 4140 was carried out for samples, which were subjected to purely elastic preload by means of 4-point-bending in the tension and compression regime
Summary
Thermal as well as thermo-mechanical processes exhibit an enormous technical and economic importance for surface optimization for improvement of the surface integrity, since most degradation processes like e.g. corrosion or crack initiation have their origin at the very surface of technical components. The selfquenching is supported by conduction of the heat into the cold material that surrounds the process zone to form martensite This local transformation is accompanied by characteristic residual stress distributions with compressive residual stresses directly in the process zone, which are balanced by tensile residual stresses outside of the laser processed material volume [1,2,3]. These tensile residual stresses are undesired; they promote the initiation of fatigue cracks at the top surface of structural component during operation and they provoke premature failure. For other surface optimization processes, like e.g. for shot peening the
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
