Journal of Welding Science

Surface roughness in the welding processes is one of the important parameters in the laser welded metal connections which affects laser beam absorption directly. When the laser beam is irradiated to the surface of the base metal, the surface roughness plays an important role in the amount of beam absorption and the amount of melting achieved and directly affects the penetration depth. The main purpose of this study is to investigate the effect of roughness mentioned above in the equal parameter for this widely used aluminum alloy. Microstructural Surveys were performed on three different roughness levels of the sample and the results obtained from the analysis of samples by optical microscope (OM), atomic force microscope (AFM) and Scanning electron microscopy (SEM) analysis showed that, increasing the surface roughness up to Ra = 0.16 micrometer, caused the greater degree of beam engagement by the surface grooves, hence more concentration of the beam photons and more melting obtained, so the depth of penetration increases by consuming a lower amount of energy.
 

Despite rapid advancement of additive manufacturing methods in recent years, sufficient research on bonding of additively manufactured materials to conventional alloys has not been conducted. This study evaluates the bonding between austenitic stainless steel L316 and Ti-6242 alloy, fabricated by electron beam melting, using the transient liquid phase (TLP) bonding method. The TLP bonding was achieved using a copper interlayer and processing in a vacuum furnace, examining the effects of process time and surface roughness on bond quality. The samples were characterized by optical and scanning electron microscopy, X-ray diffraction, shear strength testing, and surface roughness measurement. Results showed that reducing the surface roughness increased the shear strength. Additionally, processing time significantly affected the element diffusion, formation of intermetallic compounds like FeTi and TiCu, and the shear strength of the joints. The highest shear strength of 200 MPa was obtained with surface preparation by grinding and polishing and bonding at 980°C for 120 minutes.

In this study, components made of titanium alloy Ti-6Al-4V are produced using the selective laser melting process. Additionally, effects of laser power, laser scanning speed, and the amount of overlap between adjacent layers on the surface roughness of produced parts are investigated using design of experiment method based on response surface methodology. The results indicate that surface roughness of components created by selective laser melting process first decreases with an increase in laser power and then increases with further increases in laser power. Moreover, increasing the laser scanning speed leads to an increase in surface roughness of produced components. Furthermore, as the overlap of adjacent layers increases, the roughness of produced parts initially decreases and then increases. To achieve components with the least surface roughness, optimization of the process input parameters was conducted, revealing that with a laser power of 150 watts, a laser scanning speed of 500 mm/s, and an overlap amount of 67.8 microns, components made from the titanium alloy Ti-6Al-4V can be produced with a minimum surface roughness of 1.44 microns using the selective laser melting process.

The Ti-6242 alloy is of particular significance in additive manufacturing due to its high thermal resistance. However, components fabricated from this alloy using the electron beam powder bed fusion (EB-PBF) process often exhibit poor surface quality, primarily resulting from the layer-by-layer fabrication nature and and the presence of partially melted powder particles. In this study, laser polishing was employed to enhance the surface characteristics of EB-PBF fabricated Ti-6242 specimens using three laser powers (195, 260, and 325 W) and two scanning speeds (4.5 and 3 mm/s). The effects of these parameters on surface roughness, microstructure, and mechanical properties were evaluated through surface profilometry, metallography, hardness, and wear tests. The results indicated that the average surface roughness decreased by up to 93%, from 9.36 µm to 0.61 µm. Moreover, the initial α and β phases transformed into a fine, martensitic α′ phase within the polished layer, leading to a 33% increase in hardness—from 380 to 506 HV—and a significant improvement in wear resistance. Consequently, optimal adjustment of laser polishing parameters can simultaneously reduce surface roughness and enhance the mechanical performance of Ti-6242 components.