A. Czupryński

A study of modern materials for arc spraying

Results of investigations into the properties of layers sprayed with the Fe–Cr–Ti–Si–Mn alloy and Fe-based nanoalloy containing a high percentage of fine precipitates in the form of boron carbide on plates of ASTM A516 unalloyed steel, Grade 55, designed for operation at elevated temperature are presented. For arc spraying, welding equipment of the newest generation, namely EuTronic Arc Spray 4, providing high stability of the process run, and EuTronic Arc 502 and EnDOtec DO*390N metal cored wires, 1.6 mm in dia, were used. Ten-millimetre-thick layers characterized by high abrasive and erosion wear resistance were sprayed.

Welding process evaluation on the basis of video and thermal images

The progress of the welding process has a decisive impact on the quality of weld joints. Obtaining welded joints of high quality, both in terms of their mechanical and aesthetic properties, requires selection of appropriate welding process parameters and, most importantly, maintaining their stability during joint formation. While the choice of welding parameters is not a problem for an experienced welder, ensuring stability of the process is not an easy task. The stability of the welding process is affected by many interfering, often random factors, such as disruption of stability of filler feed, dirt and inaccuracy of edge preparation of the joined materials, deformation of the joined elements due to thermal expansion of the material. These factors cause welding unconformities, such as excessive melting, lack of penetration, cracks, burns, too large risers or depressions in the face of the weld, presence of bubbles, and other factors. Ensuring that high quality of welded joints is possible by controlling the welding parameters. The method of controlling welding parameters can be based on the measurement of welding parameters (e.g. current, arc voltage, and shielding gas flow). Another way to control the welding process and the welded joints is the use of visual inspection of the welding process, based on recording images of the formed welds in the visible spectrum, as well as in the nearand far-infrared spectrum, and their subsequent analysis and diagnosis. This approach is mentioned in the literature as one of the most promising ways of assessing the welding process and the welded joints. The most important aspect of using visual methods is that their use in volume production enables rapid identification of disturbances in the welding process parameters, errors in positioning of the joined elements and limiting the number of unconformities that appear throughout the series of manufactured components. Visual welding process control clearly provides increased joint quality and reduced production losses.

Repair welding of cast iron coated electrodes

Welding cast iron is a complex production procedure. Repair welding was used to repair damaged or poorly made castings. This is due to a tendency to cracking of the material during welding as well as after it. Welding cast iron can be carried out on hot or on cold. Hot welding requires high heat material and the use of welding material in the form of cast iron. In the case of cold welding, it is possible to use different materials. Mostly used filler metals are nickel and copper based. The work shows the course of research concerning repairmen of ductile iron with arc welding method. For the reparation process four types of ESAB company coated electrodes dedicated for cast iron were used with diameter 3.2 and 4 mm: ES 18-8-6B (4mm), EB 150 (4mm), OK NiCl, EŻM. In the cast iron examined during the testing grooves were made using plasma methods, in order to simulate the removed casting flaws. Then the welding process with coated electrodes was executed. The process utilized low welding current row of 100A, so there would only be a small amount of heat delivered to the heat affected zone (HAZ). Short stitches were made, after welding it was hammered, in order to remove stresses. After the repair welding the part of studies commenced which purpose was finding surface defects using visual testing (VT) and penetration testing (PT). In the second part, a series of macro and microscopic studies were executed witch the purpose of disclosuring the structure. Then the hardness tests for welds cross sections were performed. An important aspect of welding cast iron is the colour of the padding weld after welding, more precisely the difference between the base material and padding weld, the use of different materials extra gives the extra ability to select the best variant. The research of four types of coated electrode was executed, based on the demands the best option in terms of aesthetic, strength and hardness.

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.

Testing of Flame Sprayed ZrO2 Matrix Coatings Containing CaO

Presented in this article are the properties of flame sprayed ceramic coatings using oxide ceramic materials consisting of a powdered zirconium oxide (ZrO2) matrix with 30% calcium oxide (CaO) applied to unalloyed S235JR grade structural steel. A primer consisting of a metallic Ni-Al-Mo based powder has been applied to plates with dimensions of 5x200x300 mm and front surfaces of ø 40x50 mm cylinders. Flame spraying of primer coating was conducted using a RotoTec 80 torch, and an external surface was coated with a CastoDyn DS 8000 torch. Evaluation of the coating properties was conducted using metallographic testing, phase composition research, measurement of microhardness, abrasive wear resistance (acc. to ASTM G65 standard) and erosion wear resistance (acc. to ASTM G76-95 standard).

Technology of welding hard wearing plates

The technology of welding of abrasion-resisting plates with the use of different filler metals designed for providing high wear resistance of the top layer and good plastic properties of the parent material is presented. To this end, we made test joints which were subjected to metallographic examination, mechanical testing, hardness measurements and testing of wear resistance of the type metal–mineral in accordance with ASTM G65-04 standard. In each case, the weld joining the wear resistant layer was made with the use of an XHD 6710 covered electrode. For making the weld joining of the parent material of the abrasion-resisting plate, we applied austenitic and ferritic–perlitic filler materials in the form of covered electrodes and solid wires for gas shielded arc welding. The tests have shown that the XHD 6710 electrode can be used for joining of top layers of abrasion-resisting plates providing their high wear resistance. For interpasses and filler passes, it is recommended to use austenitic filler metals which are characterized by very good plastic properties. Moreover, they reduce the mixing ratio of the weld metal and the material of the abrasion resistant layer.

Research into GTA automatic soft soldering technology for solar energy collector components

This article presented research into procedures for the development of gas tungsten arc (GTA) automatic soft soldering of solar absorber components, i.e. joining of tubes to copper foil by means of brazing with SolarCast 5 soft self-fluxing solder paste. The brazing process was carried out in two ways: joining of a flat copper foil to the tube, and joining with formation of a semi-circular channel with a diameter equal to that of the tube, inside the copper foil. The properties of the finished joints were determined by means of metallographic examination, hardness measurements, static tensile tests as well as thermal conduction tests. The results of these tests proved the occurrence of an area of GTA brazing parameters which would ensure high-quality absorber joints between the tube and the copper foil.

Properties and Structure of Deposited Nanocrystalline Coatings in Relation to Selected Construction Materials Resistant to Abrasive Wear

Presented in this work are the properties and structure characteristics of MMA (Manual Metal Arc) deposited nanocrystalline coatings (Fe-Cr-Nb-B) applied to an iron nanoalloy matrix on an S355N steel substrate in relation to selected construction materials resistant to abrasive wear currently used in industry. The obtained overlay welds were subjected to macro and microscopic metallographic examinations; grain size was determined by X-ray diffraction (XRD), and chemical composition of precipitates was determined by energy-dispersive X-ray spectroscopy (EDS) during scanning electron microscopy (SEM). The size of the crystalline grains of the Fe-Cr-Nb-B nanocrystalline microstructure was analyzed using an Xpert PRO X-ray diffractometer. Analysis of the test results of the obtained layers of arc-welded Fe-Cr-Nb-B-type alloy confirmed that the obtained layers are made of crystallites with a size of 20 nm, which classifies these layers as nanocrystalline. The obtained nanocrystalline coatings were assessed by hardness and with the use of metal-mineral abrasion testing. The results of the coatings’ properties tests were compared to HARDOX 400 alloy steel.

The causes of high power diode laser brazed seams fractures of dissimilar materials

Presented in this article are the results of experiments carried out to determine the causes of braze cracking of dissimilar materials brazed with a ROFIN DL 020 high power diode laser with the use of additional powdered EN AW-1070A aluminium alloy to bond thin aluminium sheets with soft, low alloy DC04+ZE75/75 steel plate which was electrolytically coated with zinc on both sides. Presented are the results of metallographic, macroscopic, microscopic, diffractometric phase analyses of the weld joints. Metallurgical problems arising during processing as well as suggestions regarding technical aspects of laser brazing dissimilar materials in regards to their physical characteristics and chemical composition are explored.

Application of Active Thermography for Detection of Soft-Soldered Lap Joints Inner Defects

Soft soldiering is a joining technique commonly used in many areas of industry. It is especially useful for joining components susceptible to damage caused by high temperature. One of the vital issues associated with this type of joining is the possibility of the formation of hidden defects, like: cracks, lack of connection, gas voids etc. In the paper, a study of active thermography application for detection of common defects in soft-soldered lap joints is presented. Lap joints of thin copper, aluminum and high-alloy steel palates were made using solder paste in a soldering oven. Internal defects were intentionally introduced into the joints. To reveal defects, an active lock-in thermography method was applied. Various heating parameters, IR images acquisition, and processing methods were tested. In order to compare the obtained defect detection results with a benchmark, tested samples were radiographically analyzed. Results prove that active thermography methods can be applied for the detection of defects in soft-soldered lap joints. Based on the research performed, the size of defects that can be detected was estimated.