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Laser Welding of Crack Susceptible Materials

Back to Research Reports Elastic Follow-Up in the Context of Fracture Assessment Review of Process Simulations for Metal Additive Manufacturing Flaw Sizing Techniques Using Guided Waves Flaw Sizing Techniques Using Guided Waves Flaw Sizing Techniques Using Guided Waves Applications, Modelling and Manufacturing Processes for Perforated Composites - Literature Review A Review of High Power, In-Vacuum and Narrow Gap Laser Welding Processes for Thick Section Welding A Review of High Productivity Additive Manufacture Using a Hybrid Laser-Arc Deposition (HLAD) Process A Review of Micro Welding with Fibre and Disc Continuous-Wave Laser Sources A Review of Residual Stress Measurement Techniques Used for Components Produced Using the Selective Laser Melting Process A Review of the Machine GTAW Ambient Temperature Temper Bead Repair Technique for Nuclear Power Plant Components A Review of Weld Repairs of Mar-M247 and Similar Alloys Butt Fusion Welding Procedures and Test Methods Used for PE Pipes Duplex Stainless Steel Welding – A Review of Current Practices In-Bore Multi-Positional Laser Welding In-Process Monitoring of Arc Welding for Quality and Defect Detection Mechanical Fastening Technologies for Steel to Aluminium Joining in Automotive Manufacture Process Capability Study for Friction Stir Spot Welding (FSSW) Resistance Spot Welding with Transition Discs – A Review of Dissimilar Joining Using Transition Materials with Specific Reference to Resistance Spot Welding Surface Modification and Micro-Machining with Pulsed-Laser Sources Wire Fed Electron Beam Additive Manufacture – A State-of-the-Art Review
 

Laser Welding of Crack Susceptible Materials Using Tailored Energy Distributions

By Yao Ren and Max Bolut

Background

 High welding speed and low heat input are among the benefits associated with laser welding, making it an attractive fabrication process for many industries. In some applications; however, these benefits are overshadowed by weld cracking. This review considers the two principal types, solidification and liquation cracking.

During welding, as alloys solidify over a temperature range, a semi-solid region, the mushy zone, exists at the trailing edge of the weld pool. The mechanism of solidification cracking is the rupture of liquid films present in the mushy zone. Strain is normally generated by contraction, as the weld cools and, consequently, solidification cracking is controlled by both the metallurgy affecting the solidification structure and the local and global stresses and strains imposed on the solidifying joint.

Liquation cracking is also called microfissuring, edge-of weld cracking, base-metal cracking, hot cracking and HAZ cracking. It occurs in, otherwise, solid regions of the weld, which are heated by the formation of a weld bead. Liquation cracks can be formed either in the region of the parent material adjacent to the weld metal or in regions of weld metal in multi-pass welds, reheated by a succeeding weld bead. HAZ liquation cracks reflect the grain shape in of the HAZ and, in contrast to solidification cracking, are characterised by a smooth intergranular morphology.

Examples of hot crack susceptible materials include heat-treatable aluminium alloys (e.g. 2000, 6000 and 7000 series) and heat-treatable nickel superalloys (e.g. Alloy 718, CMSX-4, Waspalloy). Numerous research has found these aluminium alloys are prone solidification cracking during laser welding and Alloy 718 has been found to be particularly sensitive to liquation cracking.

This reports reviews the literature on solidification cracking, focusing on the potential for tailored energy distributions to reduce the risk of cracking when laser welding crack-susceptible materials.

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