The microstructure evolution, mechanical properties, and tribological properties of deposited metal Fe-C-Cr-Ti-B alloy by self-shielded flux-cored wire electrode (FCAW-S) with the introduction of exothermic addition and without it are investigated. Experimental studies showed that the introduction of CuO -Al exothermic addition in the composition of the wire core filler reduced the grain size of the deposited metal. Furthermore, X-ray diffraction analyses show that the boride layer contained FeB, Fe2B, and Ti(C, N) phases. Depth-sensing indentation was used to determine hard phase properties (hardness, Young's modulus and plasticity coefficient). It was shown that introduction of CuO -Al exothermic addition in the core filer increased the mechanical properties of deposited metal. The latter can be explained by the grain size decrease, as well as a change in the phase composition of the deposited metal due to additional copper alloying. This transformation is accompanied by an increase in hardness and in the Young's modulus. Tribological tests showed the effectiveness of introduction of the exothermic addition CuO -Al into the filler core for increasing the wear resistance under conditions of 3-body abrasive particle wear.
The paper the results of research is presented and the level of influence of the parameters of surfacing and the amount of exothermic mixture in the composition of self-shielding flux-cored wire on the deposition rate factor and spattering factor are analyzed. The analysis of the experiment was performed using the Taguchi method, in addition, to determine the influence of individual factors on the studied parameters (ad, ψS), analysis of variance (ANOVA) is fulfilled. It was found that for the deposition rate factor, according to the degree of influence the factors are distributed in the following order − WFS, B, CTWD, Ua, and for the spattering factor − Ua, B, CTWD, WFS. According the analysis of variance (ANOVA) of the experiment results are determined that the greatest impact on the deposition rate factor (ad) has the wire feed speed (WFS − 53.98%), the amount of exothermic mixture in the core of flux-cored wire (B − 27.3%) and contact tip to work distance (CTWD − 22.75%) have less influence, and the influence of the arc voltage (Ua) can be neglected since its contribution is only 5.82%. The arc voltage (Ua) has a high influence on the spattering factor (ψS), whose contribution is more than half (60.19%), the amount of exothermic mixture in the charge of flux-cored wire (B) has less influence, whose influence is (22.38%), while contact tip to work distance (CTWD) and wire feed speed (WFS) have minor influence and are respectively 11.55% and 5.88%. Technologically acceptable modes of surfacing are determined (contact tip to work distance CTWD = 35 mm; flux-cored wire feed speed WFS = 124 m / h; arc voltage Ua = 28V) and amount of exothermic mixture in the core of flux-cored wire, which significantly influences on the indexes of deposition rate factor and spattering factor. Models of the 2nd order of dependence on the two most significant factors for the indexes аn and ψр are constructed.
An important issue in the processes of strengthening and restoration of surfaces exposed to abrasive, abrasive-corrosive and hydroabrasive wear, using the process of self-protective flux-cored arc welding (FCAW), is to increase the productivity of hardfacing and the quality of the hardfacing metal. The literature review showed that one of the ways to increase the productivity of hardfacing and improve the quality of the hardfaced metal is to add an exothermic mixture to the core filler of flux-cored wire electrode. The effect of composition of filler core during FCAW on the fusion parameters, namely the addition of exothermic mixture (TM), the ratio of exothermic mixture components (CuO/Al), and the ratio of exothermic mixture oxidant to carbon content in the core composition (CuO/C) has been studied. It has been found that the optimum areas for the deposition rate (Gd), deposition factor (ad) and spattering factor (ψs) are observed for the following values of the core components: TM = 25…39, CuO/C = 5…6, CuO/Al = 3…4.
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