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This paper deals with a systematic metallurgical analysis of laser remelted surfaces on the hot work tool steel 1.2343 (AISI: H11). There are novel techniques using laser remelting for polishing surfaces using a constant laser beam power or for structuring surfaces using a modulated laser power. Basic properties, e. g. residual stresses, retained austenite, micro-stresses, microstructure, chemical composition and micro-hardness of the remelted near-surface layers are analyzed for different sets of procedural parameters such as laser power, laser beam diameter and number of repetitions. A carbon depleted area was found close to the remelted zone. The surface residual stresses tend from tensile to compressive and the content of retained austenite is lower when increasing both laser beam diameter and laser power. The formation of surface residual stresses is explained by a combination of shrinkage stresses and transformation stresses. The residual stresses tend from tensile to compressive with increasing number of repetitions, which can be explained by a preheating effect. A linear correlation between the measured surface hardness and the peak half width acquired by X-ray diffraction was found

Abstract.A new approach to structure metallic surfaces with laser radiation is structuring by remelting. In this process no material is removed but reallocated by melting. The laser power was adapted linearly to the increasing laser beam diameter for laser remelted (polished) samples. A carbon depleted area could be found close to the remelted zone accompanied with a local minimum in hardness. The surface residual stresses tend from tensile to compressive with increasing laser beam diameter/laser power and number of repetitions for laser structured and laser remelted samples. The residual stresses are a result of combined shrinkage (tensile) and transformation (compressive) stresses. IntroductionProperties and functions like abrasion and corrosion resistance, haptics and the visual impression of a part are strongly influenced by its surface. Therefore, many parts have structured surfaces that are wavy or serrated. Special textures are often used, like leather or textile surfaces. Grips and handles are fluted to prevent slipping.

Micromechanical material models have been established as a powerful tool for the prediction of the ductile fracture resistance. Suitable damage parameters of the Gurson model can be obtained from small volume specimens like tensile, Charpy or subsized Charpy specimens and then applied to predict transferable J-resistance curves as obtained from standard fracture mechanics specimens. In this paper dynamic tests on subsized Charpy and precracked bend specimens, SE(B), as well as static and dynamic experiments on tensile specimens for the ferritic steel A533B (HSST 03), are presented and analyzed. Two- and three-dimensional finite element models are used to determine the stress-strain behaviour and strain rate sensitivity and to find a set of damage parameters which explains the results. These parameters are then used to predict a J-resistance curve representative for a compact specimen C(T)25.

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