Robert Starosta

This work proposes using acoustic emission during a static tensile test to determine the stress characteristics of the initial phase of the destruction process of elements printed using the material extrusion (MEX) additive method at various printing parameters. The changed parameters were layer height, print orientation, filling ratio, and nozzle temperature. ABS material was chosen for printing. The experiment was carried out according to the Taguchi plan. The analysis of the results showed that changes in printing parameters significantly impact the mechanical properties of the tested elements. The parameter that had the greatest impact on strength was the filling ratio. Maximum tensile strength was achieved with the following printing parameters: 0.24 mm layer, 30°, 100% infill, 275 °C, concentric pattern. The results can be the basis for optimizing the additive printing process and improving the efficiency and reliability of manufactured components. The results of recorded acoustic emissions during strength tests allow the identification of stresses characteristic of the initial phase of the destruction process of the tested material. This phase is the elastic-visco-plastic transition, and the use of the AE method enables its detection 2–5 s earlier than the static tensile test. This allows us to determine the safe range of stresses when using the mentioned materials, which is particularly helpful in designing structures or spare parts. The test results showed that the critical stress for the investigated components is approximately 6 MPa, and exceeding this value is associated with the risk of unsafe operation.

Weld surfacing is the process of applying a layer of metal to the surface of metal objects by simultaneously melting the substrate. As a result of this process, the metal content of the padding weld can be as high as several tens of percents. It is a method used to regenerate machine parts and improve the properties of the surface layer, increasing its resistance to abrasion, corrosion, erosion, and cavitation. It also supports the repair and creation of permanent protective coatings in the engineering, automotive, energy, and aerospace industries. This makes it possible to repair damaged parts instead of completely replacing them, saving time and production costs. Plasma surfacing technology is used for components that require high hardness and corrosion resistance under various environmental conditions. Plasma wire surfacing is not sufficiently presented and described in the current literature, which creates problems in determining the appropriate process parameters. The influence of variable plasma surfacing parameters on steel C45 significantly affects surfacing weld geometry, the dilution factor, and microhardness. Higher currents can increase the dilution factor, integrating more base metal into the weld pool, which may alter the chemical composition and mechanical properties of the weld. Variations in surfacing speed and heat input also affect the microhardness of the surfaced joint, with higher heat inputs potentially leading to softer welds due to slower cooling rates. Optimizing these parameters is essential to achieving desired surfacing weld characteristics and ensuring the structural integrity of C45 steel joints. This paper presents the influence of varying plasma surfacing parameters on the surfacing geometry, the dilution factor, and microhardness. The tests were carried out on a Panasonic TM-1400 GIII automated surfacing machine with CastoMag 45554S solid wire as the filler material. Flat bars of C45 steel were prepared, and then the variable parameters of the surfacing process were developed. Tests were carried out to determine the dilution factor, followed by microhardness measurements. The results showed a significant dependence of the effect of the parameters on the surfacing geometry and the dilution factor.

The prerequisite of the weld bead finishing is intricately linked to the quality of the welded joint. It constitutes the final, yet pivotal, stage in its formation, significantly influencing the reliability of structural components and machines. This article delineates an innovative post-weld surface finishing method, distinguished by the movement of a specialized cutting tool along a butt weld. This method stands out due to its singular approach to machining allowance, wherein the weld bead height is considered and eradicated in a single pass of the cutting tool. Test samples were made of AISI 304L, AISI 316L stainless steels and EN AW-5058 H321, EN AW-7075 T651 aluminum alloys butt-welded with TIG methods. Following the welding process, the weld bead was finished in accordance with the innovative method to flush the bead and the base metal’s surface. For the quality control of welded joints before and after the weld finishing, two non-destructive testing methods were chosen: Penetrant Testing (PT) and Radiographic Testing (RT). This article provides results from the examination of 2D profile parameters and 3D stereometric characteristics of surface roughness using the optical method. Additionally, metallographic results are presented to assess changes in the microstructure, the microhardness, and the degree of hardening within the surface layer induced by the application of the innovative post-weld finishing method.

The surface of machine elements is changed to improve their mechanical properties. Ceramic-metal composite coatings are mainly used to increase the durability of machine parts. Therefore, new materials are constantly searched for application in the future development of metal and ceramic composites. The nickel and iron elements are usually used as a base and Al₂O₃ as tough particles. The welding technology for applying alloy and composite coatings is widely used. The common technology used to apply composite coatings is thermal spraying. It is a simple technology and very useful for the production or regeneration of machines. The surface layer is very rough and porous after applying the coating by thermal spraying. In order to obtain the proper surface quality of alloy and composite coatings, after-machining should be used. Many parts of machines strive to achieve an accurate surface. Therefore, a certain roughness is often required. The arithmetic mean of the ordinates of the surface roughness profile was (Ra = 0.16–1.25 μm). The article presents the influence of finishing on the roughness of the surface layer of the coating. After plastic working and machining, the roughness of the surface layer of the coating was reduced. However, it can be seen that, after plastic working, there is a strengthening of the surface layer of the coating and most of the pores were closed.

In the machine, metallurgical, and shipbuilding industries, steel products with alloy and composite coatings based on nickel may be used. It is expedient to improve the physicochemical properties of the surface layer of products as they have a significant roughness value after thermal spraying. It is therefore important to finish the layers applied by flame spraying, where machining is used for this purpose. However, it causes a loss of coating material, which is quite expensive. Therefore, in order to reduce costs and improve the quality of the surface layer, the finishing treatment of nickel-based coatings by means of plastic working is used. Two types of plastic working were proposed: rolling and burnishing. Numerical and experimental tests of the plastic processing of alloy coatings were carried out. The roughness of the coatings after rolling decreased to 1/25 and 30% strengthening of the alloy coating matrix was determined. After burnishing, roughness was reduced to 1/12 and the alloy coatings were strengthened by 25%. Plastic working by rolling and burnishing has a beneficial effect on the surface quality of the workpiece, not only by significantly improving the roughness, but also by increasing the strength properties of the surface layers.

Due to the paramagnetic properties and the ability to passivation, for the production of hulls of some vessels (mainly warships), corrosion-resistant (stainless) steels with austenitic structure are used. This article describes the influence of seawater salinity on selected corrosion properties of high-alloy steel X5CrNi 18-10 (304). The average salinity of the seas is taken as 3.5% content of sodium chloride. Corrosion rate of the tested material was evaluated in an aqueous solution of sodium chloride was evaluated. The NaCl concentration in corrosive solutions was 0.7%, 1.4%, 2.1%, 2.8%, 3.5%, 4.2%. Corrosion tests were performed using the potentiodynamic method. The range of electrochemical potential changes was E_corr ±150 mV. Corrosion rate was assessed on the basis of corrosion current density measurements. Corrosion potential values against the saturated calomel electrode were also determined. Based on the obtained measurement results and non-parametric significance tests carried out, a significant influence of seawater salinity on the value of corrosion current density and corrosion potential was found. The highest value of corrosion current density (j_corr), and thus the highest corrosion rate, was recorded for 3.5% NaCl solution. In the concentration range from 0.7 to 3.5% NaCl in solution, the corrosion rate of austenitic steel increases. A further increase in salinity of electrolyte results in the inhibition of corrosion rate of steel. There is almost a full negative, linear correlation between the proportion of sodium chloride in the corrosive solution and the value of corrosion potential. Along with the rise in the salinity of seawater, increase the electrochemical activity, and thus the corrosion susceptibility, thus the corrosion susceptibility, of the austenitic steel X5CrNi 18-10 was observed.

Hulls of ships are often made of steel, which are produced under the supervision of classification societies. Usually, the hull steel of ordinary strength category A is used for the ship's shell (the yield strength is 235 MPa and the impact strength 27 J at 20ºC). Vessels sail in sea areas with various levels of salinity and thus with different corrosiveness. The average salinity of the seas is taken as 3.5% content of sodium chloride. This article presents the results of corrosion tests of S235 JRG1 steel in an aqueous solution in which the mass fraction of sodium chloride was: 0.7%, 1.4%, 2.2%, 2.8%, 3.5% and 4.2%. Corrosion tests were performed using the potentiodynamic method. As parameters characterizing the corrosion properties of the tested steel, the corrosion current density and corrosion potential were assumed. Statistically significant influence of seawater salinity on the corrosion properties of hull structural steel of ordinary strength of category A was found. The highest value of the corrosion current density was observed in the solution containing 3.5% NaCl mass fraction was observed. In seawater with a sodium chloride content in the range of 0.7 to 3.5%, an increase in the value of the corrosion current density was observed, along with the increasing share of NaCl. In seawater with higher salinity, the corrosion rate was reduced. The corrosion potential of S235JRG1 steel decreases with the NaCl content in the corrosive solution. The susceptibility of this material to corrosion in seawater increased.

Purpose: In the paper effect of pre-heating the steel substrate on the adhesion of thermally sprayed Ni-5%Al alloy coatings was presented. The reason for the topic was the discrepancy between the literature data on the effect of the preheating of the substrate on the adhesion of the coatings and the guidelines of the coating material manufacturer. Design/methodology/approach: As a coating material the ProXon 21021 was used. It is an alloy of nickel aluminium and molybdenum. This material is often used during the regeneration of machine parts in the shipbuilding industry. The coatings by flame spraying using the Casto-Dyn DS 8000 torch were obtained. The samples were made of steel C45. The specimens to which the coating was applied were characterized by a similar surface roughness. Before applying the coatings, the samples were preheated to a temperature of 50 to 400°C. The coatings tested were similar in thickness. Adhesion strength of the coatings was determined by the pull-off method. Findings: The quantitative comparative assessment of the adhesion strength of thermally sprayed coatings can be implemented by a pull-off. The highest value of adhesion strength for coatings applied on substrates of 50, 300 and 400°C was found. Considering that the technical thermally sprayed coatings of Ni-5% Al, often require an additional machining, they must be applied to the steel substrate surface at 50°C. Research limitations/implications: The adhesion test of the coatings has not been executed in accordance with the requirements of PN-EN 582 Thermal spraying - Determination of tensile adhesive strength. Therefore, the quantitative results obtained are only comparative. Practical implications: The results obtained show that the regeneration coatings of ProXon 201021 material should only be applied to pre-heated by flame (among other things, to degrease the surface of the substrate) to a temperature of approximately 50°C. At the time the coatings are characterized by the greatest adhesion to the steel substrate. Originality/value: The study demonstrated the usefulness of cheaper method of pull-offs to evaluate the adhesion of flame sprayed coatings. The results show that there is no need for a pre-heating of the substrate between 150 and 250°C before thermal spraying. This article may be useful for technologists designing the process of regeneration of machine parts using flame spraying.

Coatings were turned by two tools: a) ISO 2R 2525K10, geometry and cutting parameters recommended by Messner Eutectic Castolin Company (tool angle β = 90^o, approach angle κ_r = 45^o, nose radius r_ε =0,8 mm, clearance angle α = 6^o, rake angle γ = -5^o) b) bit tool with CBN WNGA080408S01030A insert mounted in DWLNRL-2525M08 holder (cutting inserts β = 80^o, approach angle κ_r = 95^o, nose radius 0,8 mm, clearance angle α = 6^o, rake angle γ = -6^o). The influence of cutting speed, feed rate, depth of turning on the coating surface roughness was estimated. The following cutting parameters: cutting speed V_c = 45 214 m/min, feed rate f = 0,04 0,196 mm/rev, depth of cut a_p = 0,05 0,3 mm. The lowest value of the roughness R_a = 0,5μm of the coatings were obtained by using cutting tools and parameters and bit tool: V_c = 214 m/min, f = 0,06 mm/rev, a_p = 0,3 mm.

In the paper researches results of corrosion properties of Ni-Al alloy and Ni-Al-Al₂O₃ composite coatings were presented. Coatings were obtained by plasma torch. The studies in 0.01 M H₂SO₄ and 3.5 NaCl environments were realized. Measurements were made following methods: polarization and impedance spectroscopy. Rated coatings are more resistant to the 3.5% NaCl environment than the 0.01 M H₂SO₄. Corrosion current density for alloy coatings in artificial seawater was 19 μΑ/cm² and 28 μA/cm² environment acidic. Impedance spectroscopy studies showed that the alloy and composite coatings are characterized by greater charge transfer resistance in sodium chloride solution than in sulfuric acid solution. The value of corrosion potential in an environment of 3.5% NaCl is about 300 mV lower than 0.01 M H₂SO₄. Composite coatings Ni-Al-Al₂O₃ were characterized by a higher corrosion current densities and increased resistance than Ni-Al coatings in 0.01 M H₂SO₄ solution. It is related to the porosity of composite coatings. It was found little effect of oxide phase participation on corrosion current density and corrosion potential in 3.5% NaCl environment.