3.1 Microstructural characterization
Fig. 2 signifies the phase fraction of different WMs, and Fig. 3 displays the microstructure of BM, HAZ, and WM welded by neutral agglomerated flux (NAF) and neutral bonded flux (NBF).
The BM microstructure consists of primary allotriomorphic polygonal ferrite (PF) along with a small amount of pearlite (P). The HAZ microstructure is a combination of grain boundary PF and WF. These two expected microstructures are attained according to the weld cooling rate and chemical composition of BM [8]. A similar WM microstructure is achieved for both NAF and NBF, including AF and prior austenite grain boundary ferrite. The amount and type of different ferrite morphologies are approximately equal in both NAF and NBF, which means that the change in the unfused neutral flux manufacturing method does not affect the attained phases and morphologies.
By using the following equation to calculate the percent of element E transferred from flux into WM in SAW [3]:
![](data:image/png;base64,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)
That %EWM, %EBM, %EWW, and %EF are the %E in the WM, BM, WW, and active flux, respectively; D, ηE, and α are the dilution, recovery rate of element E and slag factor, respectively. This equation proposed previously by the authors since WW and BM do not have any Cr and Mo, the equation I will be simplified to
![](data:image/png;base64,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)
the slag factor and recovery rate data are calculated and reported in Table 5. This data stated that the recovery rate is reduced whenever using more than one element in the flux. Moreover, by increasing the Mo percentage in the flux, the Mo recovery rate is reduced, but the Cr’s recovery rate increased by increasing flux’s Cr percentage.
Fig. 4 demonstrates the WM microstructure welded by Cr active bonded fluxes and Mo active bonded fluxes. According to Table 5 and Fig. 2, incorporating 5 wt% FeMo into flux (ABF5Mo) causes the addition of 0.4 wt% Mo into the WM, increases the AF or carbide free bainite formation to 87%, and reduces the PF to 12% by inclusion assisted heterogeneous nucleation. Increasing flux FeMo to 10 wt% (ABF10Mo) causes insertion of 0.7 wt% Mo into WM, 28% bainite formation while decreasing AF fraction to 70% and producing a little amount of grain boundary allotriomorphic ferrite. On the other hand, utilizing 5 wt% FeCr in the flux (ABF5Cr) causes increasing WM’s Cr to 0.4 wt% and the formation of 57 vol% AF in the WM. Increasing flux FeCr to 10 wt% (ABF10Cr) cause adding 1.5 wt% Cr into the WM; as the AF decreases to 50 vol%, 46% of the microstructure comprises bainite. Compared to NBF, Cr and Mo addition are found to be quite effective in promoting AF formation. However, AF Vol% decreases by increasing the Cr and Mo content by up to 10 wt%. Moreover, the higher percentage of Cr and Mo caused bainite formation due to the effect of higher alloying elements.
Fig. 5 shows the microstructure of the WMs by simultaneous addition of the different amounts of FeCr and FeMo into the bonded flux. As 1.5 wt% FeCr and 2.5 wt% FeMo (ABF2.5) are added into the flux, 0.2 wt% Cr and 0.2 wt% Mo are transferred into the WM. ABF2.5 microstructure comprises AF morphology predominantly with 83 vol% along with 17% grain boundary allotriomorphic ferrite. By increasing FeCr content to 3 wt% and FeMo to 5 wt% (ABF5), WM’s Cr and Mo enhanced to 0.28 wt% and 0.35 wt%, respectively. In ABF5, the AF fraction of microstructure turns to 95 vol%, and the amount of allotriomorphic ferrite is further reduced to 5 vol%, and the whole microstructure morphology changes to favorable AF by the assisting of the proper size and number density of nonmetallic inclusions. Moreover, ferritic laths nucleate on larger inclusions to reduce the larger curvature of the inclusion-ferrite interface [9,27]. Large inclusions foster AF nucleation and are favored by the system, while smaller ones hinder the grain boundary migration and may be engulfed by large laths [6, 29, 30]. By adding 6 wt% FeCr and 10 wt% FeMo into the flux (ABF10), WM’s Cr and Mo increases to 0.45 and 0.61 Wt%, respectively. ABF10 samples’ AF vol% decreases to 60%, but 38% bainite forms and low strength allotriomorphic ferrite almost disappears. The effect of the simultaneous addition of Cr and Mo on the formation of AF is far better than the effect of an individual addition of these elements. Increasing FeCr and FeMo causes the reconstructive transformation of allotriomorphic grain boundary ferrite to become sluggish and promotes the displacive transformation of AF and bainite [15, 31].
More rapid cooling rates change the microstructure into acicular ferrite, and further increasing of it results in the emergence of upper bainite with little harmful microphases. Moreover, it is possible to increase the AF Vol% by increasing WM’s prior austenite grain size and oxygen content. The oxygen concentration of steel BMs is almost always less than that of the WM’s; therefore, oxygen can be a positive boon or a negative bane; it helps to have a higher number density of complicated inclusions while reducing prior austenite grain size and inclusions size [32–34]. Fig. 6 indicates the size and number density of inclusions within different morphologies. Irregular-shaped nonmetallic inclusions comprise a wide variety of oxides and compounds with various crystalline and amorphous phases [9, 22]. These inclusions are favorable sites for stimulation of AF nucleation, and their characteristics have a significant influence on the microstructure. The nature of the inclusions varies by the chemical composition of the WM. ABF5 comprises moderate inclusion number density with 95 vol% acicular ferrite, demonstrating that high inclusion number density does not necessarily cause a higher vol% of AF. Additionally, the proper inclusion size range is necessary for AF nucleation since larger ones deteriorate mechanical properties, whereas the smaller ones are engulfed by ferritic laths.
Fig. 7 reveals the EDS point scan chemical analysis of inclusions in different WMs. Oxygen content, cooling rate, alloying elements, BI, and prior austenite grain size affect the inclusion size and composition, which later manipulate the AF vol%. Inclusions have 10-15 wt% oxygen in their analysis, and according to the results, by the addition of FeCr and FeMo into the flux, Mo and Cr rich nonmetallic inclusions are formed, promoting AF nucleation. The following conditions increase the nucleation of AF fostered by inclusions: 1. Slight lattice strain misfit between the inclusions and matrix, 2. The positive thermal strain around inclusions due to the significant difference in coefficient of thermal expansion (CTE) with matrix, 3. The minimization of the interface energy, and 4. forming manganese free zone around the MnS included inclusions [23, 29]. Fig. 8 shows the results of the EDS point scan analysis of the ABF5 slag. According to the results, by adding FeCr and FeMo into the flux, 0.37 wt% Mo and 0.03 wt% Cr are lost from flux into the slag, emphasizing the role of elements recovery rate in active fluxes. Elements have different recovery rates and are affected by the presence of other elements. In addition, the Mn in the slag is 3.23 wt% by considering the slag to the WM ratio, which is a significant loss.
3.2 Tensile and indentation hardness evaluation
Fig. 9 represents the mechanical properties of the WMs, including the results of the LTT and Vickers hardness indentation test. The tensile and hardness values of the WM-NBF and WM-ABF are almost the same and higher than that of BM owing to AF’s formation without jeopardizing the toughness. The ABF5Mo enhances the hardness value of the WM’s, improves the UTS, reduces the ductility slightly, and increases the strength due to the solid solution mechanism of alloying elements and acicular ferrite formation with high dislocation density [35–37]. Further increasing in WM’s Mo content, ABF10Mo causes increasing in UTS, YS, and hardness, but elongation reduced by 50% compared to NBF. AF and the formation of bainite are the main reason behind these changes.
On the other hand, ABF5Cr increases UTS to 554 MPa and reduces the ductility by 23%. The UTS and hardness value of ABF10Cr are improved by 73% and 11%, respectively, but the elongation decreases sharply by 67% because of the reduction of AF vol% and increase of bainite. Microphases and morphologies rather than AF are detrimental to WM toughness since crack can propagate quickly through the matrix.
ABF2.5 YS, UTS, and HV improve by 28%, 17%, and 3%, while elongation decreases by 24%. ABF2.5’s AF vol% increases to 83%, enhancing the UTS. Moreover, ABF5’s YS, UTS, and HV increase by 37%, 23%, and 9%, while elongation decreases by 39% due to the high Vol% of AF of 97%. Finally, ABF10 YS, UTS, and HV rise by 56%, 35%, and 5%, respectively, but due to reducing the AF to 60% and the 38 vol% bainite formation, elongation is reduced slightly by 38%. It is found that by increasing alloying elements, hardenability increases due to the high WM’s CE, which causes the formation of bainite and an increase in UTS. The high percentage of AF, approximately higher than 70%, does not have an enormous effect on tensile properties, while the generation of bainite further increases the UTS by scarifying the elongation.
It seems that at least 50% AF, along with WF and allotriomorphic ferrite, is acceptable. On the other hand, mechanical properties can be discussed by considering the effect of nonmetallic inclusions. They also play a critical role in the toughness; hard and brittle inclusions, along with large size, promote crack nucleation and propagation through grain boundary allotriomorphic ferrite [7, 11, 13]. Therefore, optimum inclusion size and density number, which have good lattice matching with the matrix, stimulate sheaves of heterogeneously AF formation, deflecting and hindering crack propagation and arresting the cracks to maximize the toughness.
3.3 Impact toughness and fractography
The results of the CVN impact test of different WMs are presented in Fig. 9. The WM’s impact toughness of NAF and NBF is 144 and 146 J, respectively, so changing the unfused welding flux’s production method has almost no effect on the impact toughness. Compared to BM, the impact toughness of the NAF and NBF are sharply boosted by 440%.
By adding alloying elements into the flux, the impact toughness of the WMs is reduced. The result is still controversial, being both in agreement and contradiction with literature. Different BM, types, and amounts of alloying elements in the WM, welding parameters, impurities inserted in the WM by the welding flux, and different amounts of hydrogen, nitrogen, oxygen, sulfur, and phosphorus in the WM are the main reasons for the controversial results. The impact toughness of all the alloyed WMs is compared with NBF. ABF5Mo and ABF10Mo both have induced a 28% reduction in the impact toughness due to the presence of inclusions and detriment microphases. As a result, the impact toughness has experienced a slight decrease.
On the other hand, ABF5Cr impact toughness significantly decreases by 36%. By further Cr increasing, ABF10Cr impact toughness is reduced abruptly by 59% to 60 J. Both ABF10Mo and ABF10Cr comprise bainite, which includes Fe3C among ferrite phases, and the nature of cementite should be considered, as well.
ABF2.5 and ABF5 have the same impact toughness of about 115 J; however, their impact toughness is 21% lower than that of NBF. As Mo and Cr are further increased, the amount of AF decreases, which along with bainite formation, results in a 33% decrease in impact toughness. Therefore, optimum WM tensile toughness and impact toughness are achieved through a higher vol% of AF.
Fig. 10 shows the fracture surface of different WMs through the CVN impact test. All samples’ fracture mode is a combination of ductile and brittle. NBF comprises regular and elongated dimples and voids with a considerable amount of shear facets. ABF5Mo includes deeper dimples with embedded inclusions. ABF5Cr impact toughness is 93 J and incorporates higher inclusions size with a large fraction of shear facets and shallow dimples, harmful to toughness. A higher density of inclusions on the fracture surface is observed in ABF5. ABF5 has the impact toughness of 113 J; it also comprises voids and debonded particles, indicating voids nucleation and coalescence, which later give rise to crack formation [38, 39].