Development of residual stress and surface cracks in laser treated low carbon steel

• Published in: Scripta metallurgica et materialia 1991-04, Vol.25 (4), p.779-784
• Main Authors: Van Brussel, B.A., Hegge, H.J., De Hosson, J.Th.M., Delhez, R., de Keijser, Th.H., Van der Pers, N.M.
• Format: Article
• Language: English
• ISSN: 0956-716X
• DOI: 10.1016/0956-716X(91)90224-O

A low carbon steel CK22 was used, which contains approx 0.2 wt.% C, 0.18 wt.% Si, 0.69 wt.%Mn, 0.36 wt.% Cr, < 0.03 wt.% S and is practically single phase (bcc). Large residual stresses were generated during a laser treatment. These stresses are rapidly varying, indicating that one should be careful by measuring only average stresses on laser treated surfaces. Near the heat affected zone, tensile stresses are found in the order of 200 MPa. In the middle of the laser tracks there are also tensile stresses. A large number of small cracks are observed which only exist in a 1 mu m layer. These cracks have no influence on mechanical properties indicating a compressive stress state of this top layer. X-ray stress measurements indicate that the laser treatments of this particular low C steel using different laser parameters produce tensile stresses in and around the laser track which bear detrimental effects on wear performance. In contrast, laser treatments of a high C steel may lead to a compressive stress state depending on the particular scan velocities chosen. The applicability and usefulness of X-ray diffraction and line broadening measurements to obtain detailed information of the stress profiles across laser tracks and the corresponding effects of laser parameters are illustrated. Graphs, Photomicrographs. 10 ref.--M.W.C.