Abstract
The article presents the results of the laser alloying process of a ductile cast iron EN-GJS 350-22 surface with titanium powder in nitrogen atmosphere. The aim of this research was to test the influence of nitrogen atmosphere on the structure and properties of the ductile cast iron surface layer produced by a laser alloying process with titanium. The laser alloying process was conducted using a Rofin Sinar DL020 2 kW high-power diode laser (HPDDL) with rectangular focus and uniform power density distribution in the focus axis. The tests of the produced surface layers included macrostructure and microstructure observations, X-ray diffraction (XRD) analysis, energy-dispersive spectroscopy (EDS) on scanning electron microscope (SEM) and transmission electron microscope (TEM), Vickers hardness and solid particle erosion according to ASTM G76-04 standard. As a result of the laser alloying process in nitrogen atmosphere with titanium powder, the in situ metal matrix composite structure reinforced by TiCN particles was formed. The laser alloying process of ductile cast iron caused the increased hardness and erosion resistance of the surface.
Highlights
Ductile cast irons (DCIs) are alloys commonly used in industrial applications due to their high mechanical and fatigue strengths, plastic properties, low stress-concentration tendency, vibration-damping abilities and good casting properties and machinability, which make these materials relatively cheap and easy to form, even into complex shapes [1,2,3]
The shape of the fusion zones of laser-alloyed surface layers is hemispherical, which results from the fact that the main mechanism of the fluid flow during the laser alloying process is the surface tension gradient (Marangoni convection)
Based on the analysis of the achieved test results, the following conclusions have been reached: 1. The laser alloying process of the EN-GJS-350-22 ductile cast iron surface with titanium in nitrogen shielding allows for the formation of homogeneous in situ composite surface layers reinforced by TiCN precipitates
Summary
Ductile cast irons (DCIs) are alloys commonly used in industrial applications due to their high mechanical and fatigue strengths, plastic properties, low stress-concentration tendency, vibration-damping abilities and good casting properties and machinability, which make these materials relatively cheap and easy to form, even into complex shapes [1,2,3]. For some applications where the machine parts are operating under wear conditions, ductile cast irons exhibit insufficient wear resistance For this purpose, surface engineering technologies are used to improve the wear resistance of the surface, while maintaining the beneficial mechanical and plastic properties of the ductile cast iron core. Surface engineering technologies are used to improve the wear resistance of the surface, while maintaining the beneficial mechanical and plastic properties of the ductile cast iron core For these alloys, laser surface treatment technologies are commonly used [4,5,6,7,8]. The laser surface melting process of DCI surface causes up to 4 times surface hardness increase and has a beneficial effect on the tribological and erosive wear resistance [11,12,13,14]. During rapid cooling the carbon precipitates as cementite [15]
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