D. Janicki

High Power Diode Laser Cladding of Wear Resistant Metal Matrix Composite Coatings

The paper describes the application of high power direct diode laser (HPDDL), with a rectangular laser beam spot of size 1.8x6.8 mm, for the cladding of Ni-based alloy (NiSiB)+WC composite coatings. The laser cladding process was carried out with a direct injection of cladding powder into the melt pool. The influence of parameters, such as laser power beam (heat input) and WC particles size in the cladding powder on the coatings microstructure and wear properties was investigated. The microstructure and morphology of the coatings were assessed by optical and scanning electron microscopy. Wear properties of the coatings were investigated using abrasive and erosive wear tests. The results showed that a proper selection of laser cladding parameters provides non-porous coatings with excellent metallurgical bonding and a homogeneous distribution of WC particles. The dissolution of WC particles increases with the size of WC particles decreasing in the cladding powder and increasing the laser power level (heat input). The coatings containing WC particles in size range of 100-200 µm provide the highest wear resistance under erosive and abrasive conditions.

Fiber laser welding of nickel based superalloy Inconel 625

The paper describes the application of single mode high power fiber laser (HPFL) for the welding of nickel based superalloy Inconel 625. Butt joints of Inconel 625 sheets 0,8 mm thick were laser welded without an additional material. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The results showed that a proper selection of laser welding parameters provides non-porous, fully-penetrated welds with the aspect ratio up to 2.0. The minimum heat input required to achieve full penetration butt welded joints with no defect was found to be 6 J/mm. The yield strength and ultimate tensile strength of the joints are essentially equivalent to that for the base material.

Fiber laser welding of nickel based superalloy Rene 77

The study of laser bead-on-plate welding of nickel based superalloy Rene 77 using single mode high power fiber laser has been undertaken to determine the effect of process parameters, such as laser power, welding speed and laser beam defocusing, on the weld geometry and quality. Non-porous and crack-free welds can be achieved for a relatively wide range of fiber laser welding parameters. The welding speed has a major effect on the weld aspect ratio. The laser beam defocusing significantly affects the weld bead geometry, the stability of the keyhole and pore formation. The transition from keyhole mode to conduction mode welding occurs between focal point position +2.0 mm and +4.0 mm. The high porosity was observed at the focal point position of +2.0 mm. The heat input higher than18 J/mm results to hot cracking in the heat affected zone (HAZ). Moreover, it was found that the welds with the weld aspect ratio higher than 1.5 contain cracks, which propagate from the HAZ into the weld metal.

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

Direct Diode Laser Surface Melting of Nodular Cast Iron

A nodular cast iron (NCI) has been surface melted using the high power direct diode laser (HPDDL) with a quasi-rectangular laser beam spot and the uniform distribution of power. The effect of a heat input and a shielding gas on the quality of surface melted layers (SMLs) has been investigated. The microstructure of the SMLs has been assessed by optical microscopy, scanning electron microscopy and X-ray diffraction (XRD). Comparative erosion tests between the SMLs and as-received NCI have been performed following the ASTM G 76 standard test method. The HPDD laser surface melting of the NCI enables to produce non-porous layers having a hardness up to 1000 HV. It has been determined that the hardness of SMLs depends on the amount of cementite and residual austenite in the fusion zone. The SMLs produced in an argon atmosphere contain higher volume fraction of austenite, than those produced in nitrogen, and consequently have the lower hardness. With increasing heat input the hardness increases, as the result of more complete dissolution of graphite and the higher amount of cementite. The SMLs exhibited significantly higher erosion resistance than the as-received NCI for erodent impact angle of 30°, and slightly lower at 90°.

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.

GMA pad welding of aluminium bronze with nickel-based flux-core wire

In today’s industrial world, aluminium bronzes are often used in machine elements and installations working in the environment of salt water, characterised by abrasive wear, erosion, cavitation, oxidation and high corrosion. The alloying elements of cast or plastically worked aluminium bronzes are mainly iron, nickel and manganese. Aluminium bronzes are used for a variety of parts in chemical apparatus and fittings, valve housings, ship pumps, ship propellers and glass matrices. They are also used for special purpose parts made of copper and iron alloys by providing strengthened working surfaces. During the overlaying and welding of aluminium bronzes, a film of aluminium oxides, having a melting point of 2060 °C, forms on the surface of the molten pool. The high temperature renders joining of the filler to the base material rather difficult. Aluminium oxide may also become a source of defects, for example entrapped slag or gas pores. Consequently, and particularly so when welding cast copper alloys, both the to-be-welded surfaces and individual weld runs must be thoroughly and mechanically cleaned to prevent generation of defects in the welded joints. When overlaying with aluminium bronzes, however, thorough cleaning of pad-weld runs is not normally required, but if steel parts are to be overlayed, deep undercutting of the affected area, up to some 6.0 mm, and the deposition of two or three layers of the padding weld are recommended. Overlaying of machine elements and equipment made of aluminium bronze can be regarded to be either a repair or a production process. For the former case, it is recommended that the fi l lers used should be of approximately the same chemical composition as the bronze material. In the latter case, to increase the working life of parts, e.g. working surfaces of valve housings, working edges of screw propellers or glass matrices, it is recommended that fillers of nickel matrices be used. This article provides information about an investigation into the determination of optimal parameters for the GMA pad-welding of working surfaces of castings in Cu–Al (ASTM B 148 C 95800) aluminium bronze with EnDoTecDO*83 metallic flux-core wire manufactured by Castolin Co. GMA pad welding of aluminium bronze with nickel-based flux-core wire

Effect of laser alloying on heat-treated light alloys

Abstract This paper presents the results of a microstructure and hardness investigation into the surface layer of cast aluminium–silicon alloys, after being alloyed by heat treatment and/or remelted with ceramic powders, using a high power diode laser (HPDL). The purpose of this work was to determine the appropriate laser treatment conditions for laser surface treatment of the investigated aluminium and magnesium alloys. For investigation of the obtained structure, optical and scanning electron microscopy was used with energy dispersive X-ray spectroscopy microanalysis. After the laser surface treatment was carried out on the heat-treated aluminium and magnesium cast alloys, there were visible structural changes concerning the microstructure, as well as distribution and morphology of the phases occurring in the alloy, influencing the hardness of the achieved layer. In the structure, three zones were discovered with different structures and properties. Concerning the laser treatment conditions for laser-surface hardening, the laser power and ceramic powder feed rate were also studied. The structure of the surface laser track changed so that two areas of the dispersing zone were detected, where the ceramic powder particles were present. This investigation, with the application of an HPDL for Al and Mg alloys, makes it possible to obtain or develop an interesting technology that is very attractive for the automobile and aviation industries, as a next step after laser surface treatment used for steels.

Diode laser cladding of Co-based composite coatings reinforced by spherical WC particles

A laser cladding system consisting of a direct diode laser with the flat-top beam profile and an off-axis powder injection nozzle has been used to fabricate Co-based (Satellite 6) metal matrix composite coatings reinforced by spherical-shaped WC particles. Non-porous coatings with the WC fraction of about 50 vol.% and a low dissolution of the WC particles in the matrix have been obtained. The heat input level affects the degree of WC dissolution and the matrix mean free path between the embedded WC particles. Comparative erosion tests between the metallic Satellite 6 and composite Satellite 6/WC coatings showed that the composite coatings exhibit a superior erosion resistance only at the oblique impingement condition. Generally, a low erosion resistance of the composite coatings at the normal impingement is mainly attributed to a very smooth interface between the spherical-shaped WC particles and the matrix alloy.