研究目的
To indicate the possibility of predicting the microstructure and depths of re-melted zone (MZ) and heat-affected zone (HAZ) with the usage of Ashby and Esterling model and to determine the influence of carbon concentration in steel on the thickness, dilution ratio and hardness of laser-borided layers.
研究成果
The study demonstrated that the carbon concentration in steel influences the microstructure, microhardness, and temperature distribution during laser treatment. Higher carbon content resulted in increased depths of re-melted and heat-affected zones. The Ashby and Esterling model was useful for predicting the depths of these zones, although experimental results were slightly higher due to real conditions differing from the model's simplifications. Laser boriding produced layers with iron borides, enhancing hardness, with the highest hardness observed in Armco iron due to higher dilution ratio.
研究不足
The model used for calculation of temperature distribution contained simplifications, such as constant initial temperature and temperature-independent physical properties of the material. The experimental depths of re-melted and heat-affected zones were about 11% higher than the modeled depths. The high overlapping of adjacent tracks caused tempering of previously produced tracks, affecting the microstructure and hardness.
1：Experimental Design and Method Selection:
Laser heat treatment was arranged as laser remelting and laser boriding using materials with different carbon concentrations. The Ashby and Esterling model was used for predicting the microstructure and depths of MZ and HAZ.
2：Sample Selection and Data Sources:
Armco iron and C20, C45, C90 steels with various carbon concentrations were used. The chemical compositions and physical properties of these materials were provided.
3：List of Experimental Equipment and Materials:
A continuous wave CO2 laser TRUMPF TLF 2600 Turbo was used for laser treatment. The specimens were prepared with specific dimensions and treated with laser beam power, scanning rate, and feed rate detailed.
4：Experimental Procedures and Operational Workflow:
The laser treatment was performed in two ways: laser remelting of the base material and laser alloying with boron (laser boriding). The process parameters and steps were detailed, including the preparation of specimens and the application of boron paste.
5：Data Analysis Methods:
Microstructure analysis was performed using optical microscopy and scanning electron microscopy. Microhardness profiles were investigated using a microhardness tester. Temperature and cooling rate distributions were calculated based on the Ashby and Esterling model.
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