Piotr Wieciński

Ti – Al Intermetallic Layers Produced on Titanium Alloy by Duplex Method

The paper presents the results concerning the microstructure of Ti – Al intermetallic layers produced on a TA6V titanium alloy by the “duplex method”. This method combines vacuum evaporation coating of aluminum with glow discharge assisted heat treatment of the deposited films. It has been found that this combination of surface engineering techniques yields multi – layered films of the diffusive character. The films contain intermetallic phases from Ti – Al system which ensure a high microhardnes and good wear resistance. It is finally suggested that these properties can significantly widen application range of titanium alloy parts in aerospace.

Biocorrosion of 316LV steel used in oral cavity due to Desulfotomaculum nigrificans bacteria.

Corrosion processes of metallic biomaterials in the oral cavity pose a significant limitation to the life and reliable functioning of dental materials. In this article, the influence of environment bacteria Desulfotomaculum nigrificans sulfate reducing bacteria on the corrosion processes of 316LV steel was assessed. After 14 and 28 days of contact of the material with the bacterial environment, the surfaces of the tested biomaterial were observed by means of confocal scanning laser microscopy, and their chemical composition was studied using X-Ray Photoelectron Spectrometry and a scanning transmission electron microscopy. Corrosive changes, the presence of sulfur (with atomic concentration of 0.5%) on the surface of the biomaterial and the presence of a thin oxide layer (thickness of ∼20 nm) under the surface of the steel were observed. This corrosion layer with significant size reduction of grains was characterized by an increased amount of oxygen (18% mas., p < 0.001) in comparison to untreated 316LV steel (where oxygen concentration - 10% mas.). Image analysis conducted using APHELION software indicated that corrosion pits took up ∼2.8% of the total tested surface. The greatest number of corrosion pits had a surface area within the range of 100-200 μm2 .

Thermal Stability and Corrosion Resistance of Cr/CrN Multilayer Coatings on Ti6Al4V Alloy

The aim of this work was to investigate thermal stability and corrosion resistance of the Cr/CrN multilayer coatings. For this purpose, multilayer Cr/CrN coating was deposited on Ti6Al4V titanium alloy using PVD vacuum arc method. The Cr/CrN coating has thickness of 5.6 μm and was composed of 16 layers (8 Cr and 8 CrN). The Cr layers has thickness of 0.26 μm and were composed of columnar grains. CrN layer has thickness of 0.32 μm and were characterized by needle-like structure. Because of the potential application of the investigated coatings, thermal stability in temperature range of 300-500°C as well as corrosion behavior during salt fog test were analyzed.The investigation showed that microstructure of Cr/CrN multilayer coating was stable up to 400°C. In this temperature only a slight increase of thickness of transition Cr2N layer was observed. Annealing at temperature of 500°C changed the microstructure of the constituent Cr and CrN layers and caused decrease of their thicknesses due to increase of thickness of Cr2N transition layer. Annealing at 500°C also increased the hardness of Cr/CrN coating. XPS analysis revealed the presence of the CrO3 and Cr2O3 on the surface after annealing. Cr/CrN multilayer coatings exhibit also excellent corrosion resistant in salt fog test. No corrosion products was observed on the Cr/CrN coating surface after 120 hour of test.

Investigation of the Degradation Mechanism of Platinum-Rhodium Catalytic Wires during Oxidation of Ammonia Process

In our investigation we focused on effects of the degradation of Pt-Rh gauzes from three different industrial catalytic systems. The aim of the study was to compare the degree and the mechanism of degradation under different conditions (pressure, temperature, gas flow direction). The investigation was performed on about 80μm diameter wires after long (6 months) exposition to chemically aggressive environment. Microscope observations and microtomography analysis showed that all wires surfaces were strongly developed by etching and deposition processes occurring under extreme conditions. Each wire differed in rate of degradation and morphology of the characteristic cauliflower-shape growths. Also differences in elements distribution on both, surface and cross sections, were observed. Obtained results can be basis of further investigation on improvement of endurance of PtRh alloys in high temperature chemical application.

Nanomultilayer Coatings Based on Vanadium Nitride

Based on the analysis of the research directions in the field of coatings and layers with special operating properties, the production technologies of composite coatings, including the gradient, multi-layer, and multi-component coatings, should be distinct. The paper presents the results of material properties tests of a multi-layer coating Ti / TiN / TiAlNgradient / (TiAlN/VN)multinano obtained on hot working steel EN X32CrMoV3.3. The preparation of the multilayer coating was specially designed to increase the durability of forging dies in the brass forging process. The authors discuss the results of the microstructure tests for the obtained coatings (STEM+FIB) and present the hardness and Youngs modulus as a function of the distance from the surface (nanoHardness Tester CSM) and the results of adhesion tests carried out using a scratch-test method. The obtained multilayer coatings were also subject to a tribological test using a tribometer tester by DUCOM. The authors indicate that the coatings based on vanadium nitride have very high hardness and Youngs modulus (HV = 32–35 GPa, E = 420–450 GPa), a much lower coefficient of friction in combination with brass than steel, and a lower stability of these parameters at elevated temperatures. According to the authors, the coating represents an interesting material solution to increase the durability of forging dies in the process of brass forging.

The Influence of Microstructure of Nanomultilayer AlN-CrN-TiN Coatings on their Tribological Properties at Elevated Temperature

One of the most effective ways of shaping the operating parameters of functional elements is to modify the properties of a surface layer using modern technologies of surface engineering. The prospective directions in the development of surface engineering solutions are nanomultilayer coatings that enable effective shaping of surface layer properties. A very important factor in designing properties of PVD coatings, apart from their chemical composition, is their microstructure.The paper presents the influence of the microstructure of the nanomultilayer AlN-CrN-TiN coating on their tribological properties at elevated temperatures. The research methods were concentrated on the analysis of mechanical properties, microstructure, and tribological properties at increased temperatures. The studies on mechanical properties included tests on hardness using the nanoindentation method and tests on adhesion using the scratchtest method. The analysis of microstructure was performed using scanning microscopy. The tribological properties at high temperature were examined using the ball-on-disc method. The authors indicate that the AlN-CrN-TiN layers are characterised by excellent mechanical properties and tribological resistance. In this paper, the authors confirm that the microstructure of a nanomultilayer coating is important in shaping the mechanical and tribological properties of a PVD coating.

The Study on Erosive and Abrasive Wear Resistance of Different Multilayer Coatings Obtained on Titanium Alloy Ti6Al4V

One of the areas in which increased durability is of particular significance is the use of machine elements in conditions of intensive exposure to erosive wear, for example, turbine blades of aircraft engines and power turbines in ventilation systems, and machine elements working in a dusty environment. As it is apparent from the analysis of the state of the art, high possibilities to increase the erosive and abrasive wear resistance of machine elements are created by appropriately designed coatings and layers, especially multilayer coatings composed on the base of materials with different plasticity properties. This is associated with particular characteristics of this type of multilayer coatings that allow the absorption of external energy reaching the surface without causing permanent damage to the coating, while significantly reducing the erosive wear rate.The article presents the results of material research and the results of erosion test of three different materials solutions of surface engineering, i.e. multilayer coatings (Cr / CrN) x8, (TiN / ZrN)multinano and a (Ti-Al) intermetallic / AlCrTiN hybrid layer, obtained on titanium alloy Ti6Al4V. The (Cr / CrN) x8 and (TiN / ZrN)multinano multilayer coatings were obtained by arc evaporation, and the (Ti-Al) intermetallic / AlCrTiN hybrid layer was prepared using a hybrid technology combining diffusion saturation in aluminium powders and arc evaporation in a single technological process. The selected material solutions of the surface layer were subjected to the analysis of the structure by scanning electron microscopy (Hitachi 3000). Measurements of hardness and Youngs modulus were conducted using the nanohardness Tester CSM. The results of this study allowed the authors to compare the erosive wear resistance and wear resistance of selected material solutions, and this led to the conclusion that the (Ti-Al) intermetallic / AlCrTiN hybrid layer is the most effective solution.

The Influence of Thickness of Layers in the Multilayer Coating of the PN + AlCrTiNmultinano Hybrid Layer on Tribological Properties

One of the most perspective directions of the development of surface engineering is related to hybrid technologies. The best-known and widely used hybrid surface treatment technology is a combination of a gas or plasma nitriding process with the process of the deposition of hard antiwear coatings by means of PVD methods. The paper presents the influence of the thickness of layers in the multilayer coating on tribological properties of hybrid layers – PN + AlCrTiNmultinano obtained on the EN X32CrMoV3.3 hot working steel. The research methods concentrated on the analysis of mechanical properties, surface topography and microstructure, and tribological properties. The studies on mechanical properties included tests on hardness using the nanoindentation method and tests on adhesion using the scratchtest. The analysis of surface topography and microstructure was examined by scanning electron microscopy and scanning transmission electron microscopy. The tribological properties were examined using the ball-on-disc method. The coating was tested with alumina balls as counterparts at room temperature. The authors indicate that the PN + AlCrTiNmultinano hybrid layers are characterized by excellent mechanical properties and tribological resistance. In this paper, the authors confirmed that the thickness of layers in a multilayer coating is important in shaping the mechanical and tribological properties of the PN + AlCrTiNmultinano hybrid layer.

Influence of Hydrostatic Extrusion Parameters on the Microstructure and Mechanical Properties of 6082 Aluminium Alloy

The aim of the work was to optimise the Hydrostatic Extrusion, HE, parameters in terms of their influence on the microstructure and certain mechanical properties of 6082 aluminium alloy. The investigations focused on the fabrication of a nano- or ultrafine-grained microstructure of the alloy. The effects of a multi-pass process were compared with those of a one-pass process producing the same cumulated true strain of 3.75. Both the multi-pass and the one-pass deformation resulted in profound grain refinement of the alloy. The microstructure contained grains with an average size of 195 nm and 239 nm, respectively. The grain refinement brought about a significant improvement in the microhardness and tensile strength of the alloy. It should be noted that the multi-pass HE produced slightly greater improvement than the single pass process.