A. Klimpel

The effect of the method and parameters in the GMA surfacing with solid wires on the quality of padding welds and the content of the base material in the overlay

Semi-automatic, and automatic GMA methods of overlaying with solid and flux-cored wires are some of the main processes used in the production and regeneration surfacing of machine and equipment elements (Fig. 1). A wide range of filler metals is now available on the market and thus enables padding with materials of practically any chemical composition, viz. starting with ordinary carbon through high-alloy austenitic, ferritic, martensitic steels, chromium cast irons, alloys with nickel and cobalt matrices, and up to cermet layers, e.g. layers containing WC or W 2 C carbides in nickel matrix. By choosing a suitable selection of parameters, and

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...

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.

New developments in the process of the laser powder surfacing

On the basis of study in the area of Laser Powder Surfacing (LPS), a new technique of High Power Diode Laser (HPDL) surfacing was developed which combines the processes of laser alloying and laser cladding. The technique consists simultaneous feeding to the weld pool two types of consumables: solid or metal cored wire and also metal or ceramic powder. Precise control of the deposits shape and chemical composition demand stable feeding of the wire and powder into specific area of the weld pool and the powder feeding stream must be fed perpendicularly to the wire feeding direction. The basis process parameters are: laser power, traverse speed, powder and wire feeding rate, beam spot size, beam spot position. Excellent metallurgical bonding was achieved between the alloyed deposit and the substrate, and the alloyed deposits were high quality, free of pores and cracks. Metallographic examinations of cross sections of the alloyed deposits have indicated that the new technique allows precise control of chemical composition of the deposit and can be applied for producing functionally gradient materials. The best results are provided if a solid or cored wire creates the matrix alloy and the fed powder provides alloying metal or ceramic elements.On the basis of study in the area of Laser Powder Surfacing (LPS), a new technique of High Power Diode Laser (HPDL) surfacing was developed which combines the processes of laser alloying and laser cladding. The technique consists simultaneous feeding to the weld pool two types of consumables: solid or metal cored wire and also metal or ceramic powder. Precise control of the deposits shape and chemical composition demand stable feeding of the wire and powder into specific area of the weld pool and the powder feeding stream must be fed perpendicularly to the wire feeding direction. The basis process parameters are: laser power, traverse speed, powder and wire feeding rate, beam spot size, beam spot position. Excellent metallurgical bonding was achieved between the alloyed deposit and the substrate, and the alloyed deposits were high quality, free of pores and cracks. Metallographic examinations of cross sections of the alloyed deposits have indicated that the new technique allows precise control of chemical...

Study of titanium sheets HPDL welding phenomenon

Butt joints of titanium alloy Ti6Al4V (AMS 4928Q) thin sheets 1.0 and 1.5 mm thick were continuous-wave High Power Diode Laser (HPDL) laser welded. During course of experiments HPDL ROFIN SINAR DL 020 laser of maximum output power 2.3 kW and a rectangular laser beam spot of 1.8x6.8 mm at focusing distance 82 mm, and 1.8x3.8 mm at 30 mm was used. To provide precise positioning of the laser beam to weld joint and welding track, CNC positioning system was used. The heat input of surfacing was controlled by proper combination of the following parameters: laser beam spot size, beam spot position, laser power and welding speed. Bead on plate welds were produced, to avoid the influence of the sheet edges preparation, the joint fit-up, the welding gap and the laser beam alignment with the welding gap on the welding process. Special clamping device to provide total gas protection of weld root side was used and also special shape trailing shield was used to protect face area of the weld. The commercial grade argon and helium were used as shielding gases. Metallographic examinations and static and dynamic images of the weld pool have proved that the laser welding parameters have very strong influence on the shape of the weld pool, penetration depth, shape of the fusion zone and weld width.Butt joints of titanium alloy Ti6Al4V (AMS 4928Q) thin sheets 1.0 and 1.5 mm thick were continuous-wave High Power Diode Laser (HPDL) laser welded. During course of experiments HPDL ROFIN SINAR DL 020 laser of maximum output power 2.3 kW and a rectangular laser beam spot of 1.8x6.8 mm at focusing distance 82 mm, and 1.8x3.8 mm at 30 mm was used. To provide precise positioning of the laser beam to weld joint and welding track, CNC positioning system was used. The heat input of surfacing was controlled by proper combination of the following parameters: laser beam spot size, beam spot position, laser power and welding speed. Bead on plate welds were produced, to avoid the influence of the sheet edges preparation, the joint fit-up, the welding gap and the laser beam alignment with the welding gap on the welding process. Special clamping device to provide total gas protection of weld root side was used and also special shape trailing shield was used to protect face area of the weld. The commercial grade argon ...

Diode‐laser butt welding of thermoplastic sheet

Plastics constitute a very important branch of constructional materials, which find their use in practically all areas of peoples lives. The world industry produces over 1000 various grades of plastics, while, at the same time developments in modern chemistry and in the synthetic processes constantly increase their working potential. Polymers, elastomers, mixtures, polymeric compounds, or composites on polymeric matrices very often excel in their properties and prices compared to traditional, constructional materials such as steels and non-ferrous metals. The demand for plastics has been increasing in recent years at a much higher pace than that for constructional materials (Fig. 1). The high-density polyethylene PEHD belongs to that group of thermoplastic, hydrocarbon polymers which finds the highest degree of application in industry. They are used for the manufacture of foil and of other types of packaging, in the production of tubing for both drinking water and waste (including chemical), and in the manufacture of household containers (except those for milk and animal fat). Another domain in which PE-HD material is used, is the electronic and electric power industry. This is because polyethylene possesses excellent dielectric properties which remain unimpaired in humid conditions (Table 1). Laser welding joints in thermoplastic materials consists of melting the weld area by means of laser beam energy, which is absorbed by this zone, and, then, in forming a permanent bond on the solidification of the polymer. The usual sources of laser radiation energy are the solid Nd:YAG, high-power HPDL, and CO2gas lasers. 4 The nocontact, direct absorption of the laser beam energy by the weld area, transforms the former into vibrational particle energy and, in consequence, into the thermal energy which produces melting of the required volume of plastic. In most cases with thermoplastic materials, the laser beam energy, emitted by the CO2 gas lasers (X 10.6 um) is absorbed by the surface of the welded

Repair welding of cracks in engine turbine jet apparatus ring using high-power diode laser

The course of investigations on working out of technological conditions of automatic repair HPDL welding of longitudinal cracks in the web of the internal ring of the nozzle set of the TW2-117 engine turbine of the MI-8 helicopter made of EI-35(24-16-6) creep-resisting austenitic steel is described. Liquid-penetrant inspection and metallographic examination show high quality of repair joints.

Repair welding with high-power diode lasers of damaged resistance-welded joints in a jet engine's cooling jacket

The quality of a spot welded joint in the damaged cooler of a jet aircraft is tested and the procedure of its repair by means of high power diode laser welding of segmentary welds is developed. The high quality of the repair laser welds is shown.

Cold overlaying by MMA and GMA methods of defects in spheroidal-iron castings by means of flux-core wires

Abstract Depending on the composition of the material, the enamelling process is carried out at temperatures of between 500 and 900 °C. The layer of enamel, in addition to its aesthetic value (the possibility of producing films of a chosen colour), also guarantees the acquisition of working properties such as, for instance, resistance – particularly at elevated temperatures – to corrosive action of acids and alkaline compounds, resistance to thermal shocks, atmospheric corrosion, ultraviolet and infrared radiations, electric resistivity, etc. More and more often, manufacturers of cast fabrications require the surfaces of castings to be protected by enamel coatings.1,2

High-power diode-laser welding of austenitic steels

Developments in materials engineering and production technologies have made it possible to produce high-alloy steels with very desirable properties. Among such materials are the austenitic, chromium–nickel corrosion resistant alloys. Their applications are well known and include the chemical and petrochemical plant – in particular, storage and pressure vessels – pipeline systems, chemical cargo carriers, sea rig platforms, etc. To ensure that high quality welded constructions in austenitic, corrosion-resistant steels are produced, it is necessary to design methods and technologies which would guarantee both an acceptable quality of joint, and an efficient welding process. The 18-8 austenitic grade steels are regarded as weldable. The problems of hot cracking and of intercrystalline corrosion of the welded joints are, to a great extent, reduced because of the high degree of metallurgical purity of both the steels and the filler materials used, and, also, because it is possible to accurately control the linear energy of welding. The only problem that remains here, especially in the case of thin plates, is that of distortion due to welding which is linked to the high value of the coefficient of thermal expansion of the austenitic steels (18 × 10) (1/K), and their low thermal conductivity of about 15.5 (WK/m). The classic welding process used in connection with the welding of thin austenitic-steel plates is that of GTA or PTA, where, to limit the degree of welding distortion, a rigid instrumentation, pre-stressing of the joints, or efficiently cooled copper backing sheets, which form roots of joints, are used. Investigations into the weldability of austenitic steels, carried over a period of years, indicate that the fundamental condition for the production of high quality joints, and the reduction – to a minimum – of welding distortions, is the limitation on the thermal energy supplied to the welding zone. The modern solution to this problem is the use of the laser welding process and/ or the introduction of special, activating fluxes. The activating fluxes, such as, for instance ActivaTec 500, are substances containing oxides of iron, chromium, silicon, titanium, manganese, nickel, cobalt, molybdenum and calcium, halogens, and calcium and aluminium fluorides. The investigations into the GTA and PTA, carried out so far, show that coating an austenitic steel butt-joint with an activating flux will provide a threefold increase in the depth of fusion, or an increase in the rate of welding. Investigations into the effect of activating fluxes on the laser welding of plates in lowcarbon and austenitic steels were also made and showed that the depth of fusion could be increased, especially when the molten pool technique is employed. The results of an investigation into the effect of the welding parameters, used for the HPDL ROFIN DL 020 high-power diode laser welding of 3.0 mm thick, 18-8 austenitic plates – involving the use of the molten pool and the ActivaTec 500 techniques – on the quality of butt joints are presented here (Table 1, Fig. 1 and 2).