University of Miskolc Department of Mechanical Engineering Modelling of Laser Surface Treatment Tutor: Dr. Mária Kocsis Báan Consultant: Mr. Reza Roshan Mohamad Honeineh By: Mohamad Honeineh M.Sc. Thesis

Experimental Methodology Steel grades C45, C60, S100 (Hungarian standard) Workpice dimensions 60  56  10 (mm) Laser beam diametere 10 (mm) 9 combinations of technological paramerter: Laser power 1,2,3 (kW ) Sacnning rates 300,500,700 (mm/min) Surface coated by graphite

Preparation Stages Sectioning was accomplished by water jet cutting machine Grinding Rough and Fine Polishing The sectioned specimens were etched in Nital macro- & microphotos were placed in synchronization with the HV microhardness results

Laser Treated C45 Steel P = 2 kW, v = 300 mm/min P = 2 kW, v = 500 mm/min P = 2 kW, v = 700 mm/min

Experimental Results No significant changes were observed for 1 kW laser power For 2 and 3 kW laser power, the phase transformation depth decreased when the scanning speed was the fastest Slow scanning speeds caused wider and deeper hardened tracks For high laser power with fast scanning rates high hardness was achieved Homogeneous austenite was obtained at slow scanning rate

Three Dimensional Modelling The same geometry was built using SYSWELD SOFTWARE as that in the original experiments A Conical heat source was implemented into the SYSWELD by using simplified FORTRAN programming Due to the symmetry of the workpiece, the fine mesh created resembled only half the workpiece

3kW Laser Power v=300 mm/min v=700 mm/min v=500 mm/min

Time-Temperature Curves

Conical and Gaussian Model q max v=500 mm/min

Conical and Gaussian Model Time-temp. Cycles for C60 steel, at 2 kW and scanning speed 500 mm/min for: Conical heat source model Gaussian heat source model

Simulation Results Higher was the laser power, higher the temperature Spot size was greatly influenced by the laser power and scanning rate Time-Temperature Curves indicate that very fast cooling occurs Bigger thermal conductivity factor, lower was the Temperature Gaussian model obtained steeper and sharper cycles than that of a conical model Changing the absorptivity factor by 0.1 step increment results in °C difference in maximum temperature