Browsing by Keyword "Laser hardening"
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Item Laser hardening model development based on a semi-empirical approach(2012-07) Martínez, Silvia; Ukar, Eneko; Lamikiz, Aitzol; Tabernero, Ivan; Liebana, Fernando; COMPOSITEThe present research paper deals with laser surface hardening applied to medium carbon alloy steel AISI 1045. In order to control as much as possible the process, two different models were developed: a semi-empirical and a numerical model. To validate the results several experimental tests were carried out with a high power diode laser, measuring surface temperature with a two colour pyrometer. The process parameters considered in the study have been the laser power, from 1,700 to 1,900 Watt, and the interaction time, from 1 to 4 seconds, for a beam spot diameter of 10.2 mm. The results obtained in hardness value and heat affected zone depth show that the methodology explained is acceptable to evaluate laser hardening effects in an industrial application.Item Laser hardening prediction tool based on a solid state transformations numerical model(2010) Martínez, S.; Ukar, E.; Lamikiz, A.; Liebana, F.; COMPOSITEThis paper presents a tool to predict hardening layer in selective laser hardening processes where laser beam heats the part locally while the bulk acts as a heat sink. The tool to predict accurately the temperature field in the workpiece is a numerical model that combines a three dimensional transient numerical solution for heating where is possible to introduce different laser sources. The thermal field was modeled using a kinetic model based on Johnson-Mehl-Avrami equation. Considering this equation, an experimental adjustment of transformation parameters was carried out to get the heating transformation diagrams (CHT). With the temperature field and CHT diagrams the model predicts the percentage of base material converted into austenite. These two parameters are used as first step to estimate the depth of hardened layer in the part. The model has been adjusted and validated with experimental data for DIN 1.2379, cold work tool steel typically used in mold and die making industry. This steel presents solid state diffusive transformations at relative low temperature. These transformations must be considered in order to get good accuracy of temperature field prediction during heating phase. For model validation, surface temperature measured by pyrometry, thermal field as well as the hardened layer obtained from metallographic study, were compared with the model data showing a good adjustment.