A. Lisiecki

Diode laser welding of high yield steel

The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.5 mm thick butt joints of thermo-mechanically rolled, high yield strength steel for cold forming S420MC (according to EN 10149 - 3 and 060XLK according to ASTM) welded with high power diode laser HPDL ROFIN SINAR DL 020 with rectangular laser beam spot and 2.2 kW output power, and 808 nm wavelength. The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.5 mm thick butt joints of the thermo-mechanically rolled, high yield strength steel sheets for cold forming S420MC. The test joints were prepared as single square groove and one-side laser welded without an additional material, at a flat position. Edges of steel sheets were melted in argon atmosphere by the laser beam focused on the top joint surface. The test welded joints were investigated by visual inspection, metallographic examinations, mechanical tests such as tensile tests and bending tests. It was found that the high power diode laser may be applied successfully for one-side welding of the S420MC steel butt joints. Additionally it was found that in the optimal range of laser welding parameters the high quality joint were produced.

Welding of titanium alloy by Disk laser

The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.0 mm thick butt joints of titanium alloy Ti6Al4V (Grade 5 according to ASTM B265) welded with a new generation disk laser TRUMPF TRUDISK 3302, emitting at 1030 nm, with maximum output power 3300 W at circular laser beam spot, characterized by laser beam divergence 8.0 mm•mrad. The test butt joints of Ti6Al4V titanium alloy sheets were prepared as single square groove (I-type joint) and one-side laser welded without an additional material, at a flat position, using a specially designed system for shielding gas (purity 99.999%). The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.0 mm thick butt joints of the titanium alloy Ti6Al4V. Edges of the titanium alloy sheets were melted in argon atmosphere by the laser beam focused on the top surface of butt joints. The test welded joints were investigated by visual inspection, metallographic examinations, hardness and micro-hardness measurements and mechanical tests such as tensile tests and bending tests. It was found that the welding mode is a keyhole welding and providing high quality of joints requires a special techniques and conditions of laser welding, as well as special gas shielding nozzles is required.

Numerical and experimental determination of weld pool shape during high-power diode laser welding

In this paper, results of investigations on the shape of weld pool during High Power Diode Laser (HPDL) welding are presented. The results of tests showed that the shape of weld pool and mechanism of laser welding with a rectangular pattern of 808 nm laser radiation differs distinctly from previous laser welding mechanisms. For all power densities the conduction mode welds were observed and weld pool geometry depends significantly on the welding parameters.

Laser remelting of silicide coatings on Mo and TZM alloy

Characterization of top surface and microstructure of silicide coatings obtained during diffusion process of pack cementation type and laser remelting treatments was showed in this article. The basic materials were pure Mo sheet and TZM molybdenum alloy. The coatings were deposited in powder process and glazed by different types of lasers. In first step the phase’s compositions of coatings was described by XRD analysis in initial condition and after remelting process. The morphology of the coatings top surface was described as well. All types of coatings were characterized by network of cracks on top surface of the coatings. Laser treatment of the silicide top surface changed morphology of the top surface, especially their cracks network. LM and SEM analysis revealed that internal coatings morphology was very similar in all cases.

Experimental analysis of heat conditions of the laser braze welding process of copper foil absorber tube for solar collector elements

In the case of laser braze welding, the heating technology and temperature distribution in the joint have a significant impact on the joint quality of solar collector elements, especially for joints of copper foil as thin as 0.2mm and with very low heat capacity with copper tube with a diameter of 8.0mm and a thickness of 0.5mm, thus being an element of much larger heat capacity. Electrolytic copper has a high thermal conductivity in the range of 400W/mK, which further impedes the heating

A basic study on the high power diode laser welding of a titanium alloy

High power diode lasers (HPDLs) have only recently been introduced for materials processing. The advantages of HPDLs include higher energy efficiency and lower running costs. Besides, because of the mass production possibility of semiconductors, the prices of HPDL are currently dropping fast, making these lasers very competitive for future large-scale materials processing systems.This paper describes the application of High Power Diode Laser (HPDL), with maximum output power 2.3 kW and rectangular laser beam spot, for the welding of Ti6Al4V sheets, 1 and 1.5 mm thick. Bead on plate and butt welds were studied and tested using two different covering gases, He and Ar, and flow rates. A metallographic analysis of the cross-sections of welded specimens was carried out in order to measure the morphological characteristics of the welded joint, micro-hardness and tensile tests were performed to complete the mechanical characterization. The results of tests showed that the shape of weld pool and mechanism of laser welding with a rectangular pattern of 808 nm laser radiation differs distinctly from other laser welding mechanisms, reported by the same authors in previous published works.High power diode lasers (HPDLs) have only recently been introduced for materials processing. The advantages of HPDLs include higher energy efficiency and lower running costs. Besides, because of the mass production possibility of semiconductors, the prices of HPDL are currently dropping fast, making these lasers very competitive for future large-scale materials processing systems.This paper describes the application of High Power Diode Laser (HPDL), with maximum output power 2.3 kW and rectangular laser beam spot, for the welding of Ti6Al4V sheets, 1 and 1.5 mm thick. Bead on plate and butt welds were studied and tested using two different covering gases, He and Ar, and flow rates. A metallographic analysis of the cross-sections of welded specimens was carried out in order to measure the morphological characteristics of the welded joint, micro-hardness and tensile tests were performed to complete the mechanical characterization. The results of tests showed that the shape of weld pool and mechanism of lase...

The influence of laser re-melting and alloying on the structure and properties of the X40CrMov5-l steel surface layer

This paper presents the results of laser re-melting and alloying parameters on the structure and properties of the surface layer of X40CrMoV5-1 hot work tool steels, using a high-power diode laser (HPDL). Investigation indicates the influence of the alloying carbides on the structure and properties of the surface layer of the steel, depending on the kind of alloying carbides and HPDL implemented. Laser alloying of the surface layer of the steel – without introducing alloying additions to the liquid molten metal pool and across the entire range of laser power used – causes a size reduction of the dendritic microstructure in the direction of crystallization, consistent with the direction the heat is being carried away from the laser beams impact zone. Successful re-melting of the steel without introducing alloying additions into the liquid molten pool in the form of carbide powders causes a slight increase in the properties of the surface layer of the steel in comparison to analogical properties obtained through conventional heat treatment, depending on the laser beam power used for the re-melting. The increase in the hardness of the surface layer obtained throughout HPDL re-melting and alloying with carbides is accompanied by an increase in tribological properties, when compared to X40CrMoV5-1 steels processed with conventional heat treatment.

Plasma welding repair procedure for turbine jet apparatus rings in aircraft engines

The course of investigations on the development of technological conditions of manual and automatic repair plasma welding of cracks in the nozzle set of the TW2-117 engine turbine of the MI-8 helicopter made of EI 835(24-16-6) creep-resisting austenitic steel is described. Liquid-penetrant inspection and metallographic examination have shown a high quality of repair joints.

Laser welding technologies: high power diode laser application examples

In recent years, laser welding technologies have reached a stable position in the process of guaranteeing high quality and economy in many industrial applications: welding, cutting, hardfacing, alloying, remelting and heat treatment for top layers – . The only significant limitation on their common usage, especially with regard to Polish enterprises, is the high cost of laser stations, which varies from 100 to 300,000 euros, and even up to a million plus, depending on the laser type, its strength and the station’s equipment, vital in the automation and robotization of the welding process. The advantages of laser welding technologies, which result mainly from the very small linear energy of a high-energy focused laser beam, narrow heat affected zone (HAZ), minimal welding deformations and stresses, include – : . high quality of welded and repairable joints or those with alloy inserts (so-called alloyed joints) on top layers or cut edges, . the highest efficacy and easy automation and robotization, . no or very limited finishing, . very good local and operative weldability, . limited harmful effect on operators and the environment and . simple training and operation of devices.

Joining of an Ni-Al alloy by means of laser beam welding

Trials of wlding an alloy based on an Ni3Al phase matrix with a diode laser have been made. In the base metal of Ni3Al, typical casting structures have been found. The Heat Affected Zone consists of a fine-grained structure, whereas in the weld structure, columnar crystals have been observed. A possibility of joining intermetallic phase-based alloys by measn of a diode laser has been affirmed.