Experimental investigation and optimization of laser surface treatment parameters for 1.2379(AISI D2) tool steel

Laser surface treatment has been used as a cost-effective method to improve the surface qualities of materials, such as hardness, strength, roughness, corrosion resistance, chemical resistance and coefficient of friction by modifying their structure and physical features using laser beam heat. In this thesis, surface properties such as hardness and roughness of 1.2379 cold work tool steel, a commonly used material in the die and mold industries for injection mold inserts, were investigated both experimental and numerical (regression analysis, optimization) studies. In the experimental part of the thesis, 1.2379 cold work tool steel surface was treated using a commercially available industrial Ytterbium low-power pulsed fiber laser. Laser parameters including average power, repetition rate, line spacing and scan speed were considered as input parameters while hardness and roughness were used as output parameters. Input parameters used in the experiments were produced by using a 34 full factorial design. The effect of laser parameters on the surface properties of 1.2379 cold work tool steel was investigated by hardness and roughness measurements. Using the results of the measurements different regression models were conducted and the best fit was chosen. As a result of regression analysis, it is obtained that the second-order multiple non-linear model is the best regression equation for hardness and the second-order logarithmic multiple non-linear model is the best for roughness Following the experimental study and regression analysis, an optimization study was performed using Wolfram MATHEMATICA 11.3 to determine the optimum laser parameters for the hardness and roughness of 1.2379 cold work tool steel. In the optimization, Random Search (MRS), Simulated Annealing (MSA), Differential Evolution (MDE) and Nelder-Mead (MNM) methods were used for different optimization scenarios. By determining the optimum parameters, this thesis contributes to enhancing the surface properties, hardness and roughness, of 1.2379 cold work tool steel.