Papers by Author: Robert Starosta

Abstract: 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.

Abstract: 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.

Abstract: Coatings of metal and ceramic composite were applied on the steel specimens using the subsonic process of flame spraying. The specimens were then subjected to both cold and hot plastic working by rolling and also cold pressing by the hydraulic press. Plastic working is an alternative to machining, as the method of finishing of coats applied by flame spraying. The article presents the findings of the research into the possibility of using plastic working (hot and cold rolling and pressing) to obtain the corrosion properties of the flame sprayed Ni-Al alloy coatings and Ni-Al-Al₂O₃ composite coatings. The alloy coatings had a single-phase structure, of the maximum 10% aluminium solubility in the crystal lattice of nickel, whereas in the composite coatings the volume content of non-metallic material Al₂O₃ was 15% and 30 %. After finishing the adhesion reduction, cracks on the surface and cross-sections of coatings was not observed. The largest value of strain hardening of alloy coating Ni-5%Al was stated after pressing. The composite coatings obtain by flame spraying be characterized by big surface roughness (R_a = 13.3 µm). The plastic working caused decrease surface roughness. Minimum value of R_a parameter was observed after hot rolling. It was found that maximal roughness was presented after pressing. The corrosion tests were performed in 0.01 M H₂SO₄ solution by potentiokinetic technique. The article presents the effect of dispersion phase of Al₂O₃ on corrosion properties of composite coatings on the nickel base. The corrosion rate was dependent on method of plastic working. The increasing drafts resulted in rise corrosion current density and decrease in value of corrosion potential.

Abstract: In the paper researches results of corrosion properties of Ni-Al alloy and Ni-Al-Al₂O₃ composite coatings were presented. Coatings were obtained by flame spraying of "Casto-Dyn 8000" torch. During coatings flame spraying of torch was used a small distance from the substrate. Instead of commonly used spray distance 150 mm, 100 mm was used. The studies in 0.01 M H₂SO₄ and 3.5% NaCl (artificial seawater) environments were realized. Evaluated coatings are more corrosion resistant in the 3.5% NaCl environment than in the 0.01 M H₂SO₄. Corrosion current density for alloy coatings in artificial seawater was 20 μA/cm² and 223 μA/cm² in an acidic environment. The value of corrosion potential in an environment of 3.5% NaCl is about 200 mV lower than in 0.01 M H₂SO₄. Composite coatings Ni-Al-Al₂O₃ were characterized by a lower corrosion current densities and increased resistance than Ni-Al coatings in acidic environment. The presence of alumina in the coating matrix caused increased corrosion current density in sea water environment.

Abstract: Angular momentum pumps are very often applied in ships. Because the pumps are operating in hard conditions they are produced from cavitation wear-proof and electrochemical corrosion-resistant materials. The most common damage of pump shaft is neck wear in place where seals are mounted. Burnishing as modern finish plastic tooling method makes it possible to achieve high technological quality of elements. Due to many burnishing advantages, the method was proposed for treatment of angular momentum pumps shafts instead of finish machining (finish turning, grinding, lapping). The goal was to estimate optimal burnishing parameters that enable obtaining higher strength and the lowest roughness factor of angular momentum pumps shafts. Shaft necks were made of stainless steel type X5CrNi1810. Roller burnishing tool SRMD type produced by Yamato was used in the research work. Its axis was parallel to working shaft axis. During working, technological parameters such as force, velocity and feed were changed.

Abstract: The paper presents the preliminary research results that were aimed at working out a technology of the surface roughness reduction by means of plastic working methods. The intermetallic phase NiAl and Ni3Al coatings that were plasma sprayed on a flat bar made of non-alloy steel (C45) were chosen for the research. The coatings underwent plastic working with the use of press. Three specific loads were used: 500, 800, 1100 MPa. The treated coatings exhibited 70% lower surface roughness as compared to thermally sprayed layers. However, high values of relative strain of coatings ( = 0.21 – 0.62) were obtained. Plastic working resulted in the decrease of corrosive potential values and increase of corrosive current density.

Abstract: Modern materials on intermetallic matrix are in the scope of research of many scientific – research centers in Poland [1]. Intermetallic systematic alloys containing aluminium have high resistance to oxidation, abrasive corrosion and fatigue as well as heat resistance. That is why they are applied in the production of machine parts used in hard service conditions (internal combustion turbine blades, exhaust valves, turbo-blower rotors) [2]. Intermetallic coatings can be obtained by means of plasma spraying. Thermal spraying technology is widely used due to the possibility of increasing the service properties in surface layers (strength property, tribological, anti-corrosive and decorative property) as well as coating application on machine parts elements, on tools for plastic working (forging moulds busters, piston rods, gear wheels teeth, crank journals, valve seats, and combustion engine cylinders) [3, 4]. NiAl and Ni3Al coatings are characterized by high fatigue resistance, heat resistance and considerable corrosion resistance [5]. Coatings obtained by thermal spraying have high surface roughness. Thus, subsequent plastic treatment is advisable for plasma-sprayed intermetallic coatings. Therefore it is vital to define to what extent the change of unit pressure will influence reduction of surface roughness of intermetallic coatings. For this purpose experimental upsetting research was carried out on C45 steel samples having NiAl and Ni3Al coatings for the following unit pressures p = 500 MPa, p = 800 MPa, p = 1100 MPa.

Abstract: The paper presents the effect of dispersion phase of Al2O3 on selected potential properties of composite coatings on the nickel base. Coatings of Ni-Al-Al2O3 were applied on the steel specimens using the subsonic process of flame spraying. The specimens were then subjected to both cold and hot plastic working by rolling and also cold pressing by the hydraulic press. Plastic working is an alternative to machining, as the method of finishing of coats applied by flame spraying. The paper presents the findings of the research into the possibility of using plastic working (hot and cold rolling and pressing) to obtain the selected properties of the flame sprayed Ni-Al alloy coatings and Ni-Al-Al2O3 composite coatings. The alloy coatings had a single-phase structure, namely boundary solution α , of the maximum 10% aluminium solubility in the crystal lattice of nickel, whereas in the composite coatings the volume content of non-metallic material Al2O3 was: 0, 15, and 30 %.