Abstract
Joining metallic alloys can be an intricate task, being necessary to take into account the material characteristics and the application in order to select the appropriate welding process. Among the variety of welding methods, pulsed laser technology is being successfully used in the industrial sector due to its beneficial aspects, for which most of them are related to the energy involved. Since the laser beam is focused in a concentrated area, a narrow and precise weld bead is created, with a reduced heat affected zone. This characteristic stands out for thinner material applications. As a non-contact process, the technique delivers flexibility and precision with high joining quality. In this sense, the present review addresses the most representative investigations developed in this welding process. A summary of these technological achievements in metallic metals, including steel, titanium, aluminium, and superalloys, is reported. Special attention is paid to the microstructural formation in the weld zone. Particular emphasis is given to the mechanical behaviour of the joints reported in terms of microhardness and strength performance. The main purpose of this work was to provide an overview of the results obtained with pulsed laser welding technology in diverse materials, including similar and dissimilar joints. In addition, outlook and remarks are addressed regarding the process characteristics and the state of knowledge.
Highlights
In terms of mechanical properties, the optimisation of the welding parameters Metals 2021, 11, x FOR PEER REVIEWperformed in DP600 steel generated true stress values in the weld very similar 9toofth3e8 base material (BM), and the failures did not occur in the FZ [57]
The FZ of joints made with AISI 321 austenitic and AISI 630 precipitation hardening stainless steels (17-4 PH) showed refined martensite developed near the AISI 630 and delta ferrite microstructure in the centre (Figure 10A–C) [63]
When 316L stainless steel and AA1060 pure aluminium were welded in overlap configuration, the FZ displayed a wavy interface surrounded by needle-like structures of FeAl and FeAl2 phases (Figure 15E,F) [87]
Summary
Laser technology is being widely used as a joining technique in several materials, including metallic alloys. The planar mode near the FZ boundary changed to cellular dendritic in the weld centre, passing through the cellular mode In researching another significant austenitic alloy extensively applied to industrial sectors, 316 stainless steel, one study found that the pulsed laser promoted coarse grains in the FZ versus fine grains in the HAZ [2]. Martensitic stainless steels have excellent mechanical properties and moderate corrosion resistance; they have low weldability due to the characteristics of high hardenability and susceptibility to hydrogen induced cold cracking [59] In this sense, the pulsed process was used for joining cylinders of 420 alloy and the BM microstructure changed from ferrite matrix with precipitation of M23C6 carbides to fine martensite, δ-ferrite, and some retained austenite in the FZ (Figure 9M,O) [60]. The values of hardness observed in the regions are summarised in this table
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