Abstract
The paper presents the study results of laser modification of FeB–Fe2B surface layers produced on Vanadis-6 steel using pack cementation method. Microstructure, x-ray phase analysis, chemical composition study using wave dispersive spectrometry method, microhardness, corrosion resistance as well as surface condition, roughness, and wear resistance were investigated. The diffusion boronizing processes were performed at 900 °C for 5 h in the EKabor® powder mixture. The boronized layers had a dual-phase microstructure composed of two types of iron borides, FeB and Fe2B, and their microhardness ranged from 1800 to 1400 HV. The laser surface modification was carried out on specimens after diffusion boronizing process using CO2 laser with a nominal power of 2600 W. Laser beam power used in this experiment was equal to 1040 W and was constant. While the three values of scanning speed were used: 19, 48, and 75 mm/s. During laser modification, the multiple tracks were made where distance between of axis tracks was equal to 0.5 mm. As a result of this process, microstructure consisted of remelted zone, heat-affected zone, and substrate was obtained. In remelted zone, the boron-martensite eutectic was observed. Boronized layers after laser modification were characterized by the mild gradient of microhardness from surface to the substrate and their value was dependent on the scanning speed used and was between 1700 and 1100 HV. Corrosion resistance tests revealed reducing the current of corrosion in case of laser modification process. Wear resistance of laser modified specimens was improved in comparison to diffusion boronized layers.
Highlights
Methods and techniques of surface engineering are applicable mainly for materials used to produce machine parts and tools where the fulfillment of certain performance criteria is necessary
It has been observed that the surface of specimens after the laser modification was characterized by lack of defects such as cracks or porosity, which are sometimes created by wrong selected parameters of laser beam
This paper presents the quantitative results of chemical composition in the form of table
Summary
Methods and techniques of surface engineering are applicable mainly for materials used to produce machine parts and tools where the fulfillment of certain performance criteria is necessary. 1600 HV and Fe2B with microhardness ranged from 1600 to 1400 HV are formed [1,2,3,4,5] Besides advantages such as high hardness, wear resistance, and resistance to chemical corrosion in many alkaline and acid solutions, the boronized layers show some disadvantages. In the case of two stage processes which consisted of diffusion boronized and laser modification, authors can find several uses These can be, e.g., the tools for metal forming processing as for stamping, forging, or extruding. Surface layers after diffusion boronized and laser modification seems to be chemically and mechanically resistant This type of surface layers may be prepared on alloy and non-alloy tools steel. Studies were focused on selected properties of produced layers such as microhardness, wear resistance, surface condition, chemical and phase composition, as well as corrosion resistance.
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