Journal of Welding Science

---

In this research, artificial neural network (ANN) and genetic algorithm (GA) were used in order to produce and develop the NiAl intermetallic coating with the best wear behavior and the most value of hardness. The effect of variations of current, voltage and gas flow on the hardness and wear resistance were optimized by ANN and GA. In the following, the optimum  values of current, voltage and gas flow were obtained 90(A), 10(v) and 9 (Lit/min), respectively. Then, the wear behavior in the environment temperature and high temperature for optimized NiAl compound was compared with two other experimental samples.

---

In this research, the dissimilar welding of St52 plain carbon steel to W400 wear resistant steel and its effect on the microstructure and wear properties of the wear resistant steel was investigated. The wear resistant steel was produced via direct quenching with nominal hardness of 400 HB. Gas tungsten arc welding was used for joining process. The results showed that welding led to hardness reduction, wear rate increase and also significant changes in microstructure of the heat affected zone of the wear resistant steel. According to the results, by increasing the heat input for about 9%, the hardness and wear rate of the heat affected zone was decreased 8% and increased 250%, respectively. According to the scanning electron microscopy observations the main wear mechanisms of the base metal were adhesion and abrasion. However, the wear mechanisms of the heat affected zone were mainly adhesion and delamination. By increasing the heat input, the delamination was increased significantly. 

---

The purpose of this study was to examine the effect of adding Nano particles such as Nano Carbon Tube during Friction Stir Welding (FSW) on dissimilar Al alloy joints. More specifically, both FSW and Friction Stir Processing (FSP) were performed simultaneously to investigate the effect of adding Nano particles on mechanical properties and microstructure of the weld zone for joining AA5754-H22 and AA6063-T4aluminum alloys. Reliability of the joints was tested by non-destructive tests such as visual inspection, ultrasonic, and radiography. The global mechanical behaviors of dissimilar welds were similar to that of the base material. Important losses in ductility were also reported for dissimilar welds. Microstructural evaluation of fractured surfaces indicated that ductile fracture was the major mechanism of similar and dissimilar welds. We expected that the locks for dislocation moving would improve the mechanical properties of the weld zone. Also, the friction coefficient in the two-passes welded sample was about 30% lower than the friction coefficient of the base metal. On the bases of the wear resistance of hardness and the coefficient of friction, it was concluded that the wear resistance of the surface Nano-composite produced had also increased in the stir zone.

---

In this study, formation of Fe₃Al and (Fe,Cr)₃Al intermetallic compounds and the effect of Cr on microstructural and mechanical properties of Fe-Al cladding system such as hardness and wear resistance, were evaluated. For this purpose, first, iron and aluminum powders were mixed without chromium powder and in the second stege with the addition of chromium powder in high energy planetary ball mill, and Fe₃Al and (Fe,Cr)₃Al intermetallic compounds were synthesized. The preplaced powders were cladded on the surface of CK45 steel using gas tungsten arc welding process. The microstructure, formed phases and properties of the cladded layers were studied by optical microscope, scanning electron microscope, X-Ray Diffraction, micro and macro hardness, energy dispersive X-ray spectroscopy (EDS) and pin on disk wear test at temperatures of 25, 250, and 500 ᵒC. It was found that the microstructure of Fe-Al binary cladding contained Fe₃Al dendrites with non-epitaxial growth. This non-epitaxial growth resulted from the difference in the chemical composition of the coating and the substrate at the interface between the coating and the substrate, which caused the formation of new crystals at the interface. However, the microstructure of Fe-Al-Cr ternary cladding contained martensitic blades within (Fe,Cr)₃Al matrix. The results of hardness tests revealed that the hardness of ternary cladding is twice as compared with the binary cladding (30 and 60 HRC for binary and ternary claddings, respectively). Also it was found that the presence of Cr element in Fe-Al cladding improved the wear resistance of deposited layers. The predominant wear mechanism of Fe₃Al pin was adhesive, while for (Fe,Cr)₃Al pin moreover adhesive wear, micro-plowing abrasive wear was also seen. The mass losses of both pins were maximum at ambient temperature and minimum at temperature of 500 ^oC.
 

---

In this research, copper/silver-silicon carbide Cu-Ag-SiC composite was prepared by the friction stir processing (FSP). For this purpose, nanometer and micrometer SiC particles were used as reinforcing particles. In order to evaluate the microstructural properties, X-ray diffraction (XRD) analysis, scanning electron microscope and optical microscope were employed. Evaluation of mechanical properties through microhardness measurement, tensile test and pin on disc test were utilized to evaluate the wear behavior of the composite. The results of X-ray analysis revealed the presence of two phases of CuAg solid solution along with SiC particles, which indicated the formation of Cu-Ag-SiC composite. The addition of nano-particles led to a significant decrease in the intensity of peaks compared to micro-particles. This indicated a decrease in the grain size of the CuAg matrix. Using the FSP in the presence of reinforcing particles and without it led to a decrease in the crystal size and average grain size compared to the sample without FSP. So that the grain size of the sample without FSP and the FSPed sample without reinforcing particles and with nano-reinforcing particles were found to be about 46.3, 19.2 and 3.6 µm, respectively. The wear mechanism in the sample before FSP was adhesive wear due to its soft nature of the matrix, and after FSP in the sample without reinforcing particles, the adhesive wear decreased and due to the addition of silicon carbide micro and nano- particles reinforcement, the wear mechanism in entirely altered to abrasive wear. Overall, it can be stated that the addition of silicon carbide nanoparticles by FSP leads to the fabrication of  Cu-Ag-SiC composite with high mechanical properties.

 

---