INŻYNIERIA MATERIAŁOWA 6/2018

Katarzyna Dyndał
Characterization of a-C:N:H, a-SiNx:H and a-SiCx:Ny:H layers deposited on various substrates
Charakterystyka warstw a-C:N:H, a-SiNx:H i a-SiCxNy:H osadzanych na różnych podłożach
DOI 10.15199/28.2018.6.1

Julian Plewa, Elżbieta Augustyn, Michał Żelechower
Partial crystallization of the erbium/ytterbium co-doped oxyfluoride glass
Kontrolowana krystalizacja współdomieszkowanych erbem i iterbem szkieł tlenofluorkowych
DOI 10.15199/28.2018.6.2

In the paper there are described LIBS (Laser-Induced Breakdown Spectroscopy) emission spectra of a graphene paper (new engineering material) and a composite material consisiting of two layers of C0.90 220 g/m2 carbon divided by a polymer layer of a foamed polyvinyl chloride of the Herex 70 g/m2 type. In the graphene spectra oscillation-rotational transitions in CN and CH compounds and in C2 and N2 molecules were found. A clear difference between graphene and composite spectra was found - in the composite spectrum much stronger atomic carbon signal as compared to graphene was seen. This can be related with a difference in the allotropic structure of a carbon molecules and a higher temperature of a plasma generated on a composite surface. The aim of the paper was to show capabilities for application of LIBS in the investigations of thin and inhomogeneous molecular layers in compounds of carbon and other elements in the graphene paper and the carbon C/Herex/C composite.

Impairment of the cardiovascular system is a major cause of mortality in humans. Cardiac implants are made mostly of titanium and its alloys and various methods have been used to improve their surface properties. Titanium nitride — TiN and titanium oxide — TiO2 surface layers are promising materials to improve biocompatibility in this respect. Modifying their surface properties in the nanoscale may impact their protein adsorption and cellular response to the implant. Nitriding and oxynitriding processes in low-temperature plasma, also involving the use of an active screen, seem to be prospective methods in the production of titanium nitride and oxide forming an diffusive outer zone of titanium nitride TiN (nanocrystalline) + Ti2N + α-Ti(N) or oxynitrided TiO2(nanocrystalline) + TiN + Ti2N + α-Ti(N) surface layers on titanium alloy. Also a hybrid method that combines oxidizing and the RFCVD process for producing a-C:N:H (amorphous carbon modified with nitrogen and hydrogen) + TiO2 (nanocrystalline titanium oxide-rutile)-type composite surface layers on NiTi shape memory alloys is noteworthy in the context of medical applications. The paper presents the characteristics of these diffusion multi-phase layers in terms of their microstructure, topography, hardness, residual stress, corrosion and wear resistance, wettability as well as biological properties such as: adsorption of proteins — fibrinogen and albumin, and platelet adhesion during interaction with blood components (human plasma and platelet-rich plasma). The results suggest that these layers, produced using the new hybrid processes, exhibit a high potential for improving cardiac implant properties. The article is based on research carried out by the authors and the interpretation of the obtained results is made on the basis of literature data regarding the surface layers of titanium oxides and titanium nitride produced by various methods.

Coatings of hydrogenated silicon nitride and silicon carbonitride find numerous applications stemming from their various useful properties which can be easily modified during the deposition process. In this work, the effect of discharge power on the physical properties of the coatings synthesized from organosilicone precursors is presented. Compared to explosively flammable silane, these precursors are safe and do not require costly safety measures installed in the equipment. The coatings investigated were deposited from hexamethyldisilazane (HMDSN) using radiofrequency plasma enhanced chemical vapour deposition in an atmosphere of such working gases as nitrogen, ammonia and hydrogen. HMDSN constitutes a valuable precursor since its saturated vapour pressure is relatively high (1.8 kPa at 25°C) and its molecule contains both silicon and nitrogen atoms. The coatings synthesized were broadly investigated with the help of such analytical techniques as variable angle spectroscopic ellipsometry (VASE), UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of the glow discharge power on the coatings chemical structure and, therefore, on the magnitude of their refractive index was studied. It has been demonstrated that the discharge power strongly affects quantitative proportions between Si–N, Si–NH–Si, Si–O chemical bonds in the resulting films which, in turn, determine their index of refraction.

The paper presents the results of tests of bearing steel grade 100Cr6, which corroded during maritime transport. As a result of the tests, it was found that the surface was subjected to temporary protection with the use of a preservative. Its presence on the surface contributed to the formation of filiform corrosion. The resulting corrosion changes are on the surface and do not propagate into the element. The microscopic image of the resulting changes also indicates the rapid progress of the filiform corrosion, which is manifested by the formation of linearly arranged corrosion micro pitting. The primary carbides present in the microstructure are cathodic precipitates in relation to the matrix and are not subject to digestion. In the forehead of the corrosion thread, an increased content of chlorine and the presence of sulphur were found in comparison to the tail of the thread.

The paper presents the results of studies on the influence of the addition of TaC–NbC on WC–5Co cemented carbides produced by pulse plasma sintering, and their effect on the hardness of cutting inserts and durability of cutting edges made from WC–5Co and WC–5Co–xTaC–NbC (x = 0.5, 2.5, 4.5) cemented carbides. The Vickers hardness was measured according to the PN–EN 23878:1996 standard and the durability was measured during machining using a conventional lathe where the shaft (counter-specimen) was made from 1.4541 stainless steel. The obtained results clearly show the positive effect of the addition of TaC–NbC on the hardness of cutting inserts and durability of cutting edges. The hardness increased by 5% for the WC–5Co–2.5TaC–NbC insert in comparison to pure the WC–5Co insert. The durability of the cutting edges also increased by 20% for the WC–5Co–2.5TaC–NbC insert.

This paper presents an attempt at the numerical modelling of a model that has been developed for a glass-fiber reinforced epoxy laminate (10-layer) square plate, supported on a circular support and loaded centrally with a spherical indenter. The determination of the stress corresponding to the initiation of the material failure process under such loading conditions has also been presented. ALGOR software was used for the numerical modelling. It was found that the performed analysis can be efficiently used to evaluate the properties of a material subjected to a compound stress state. This has been proven effective to determine the stress level in the material. The analysis of the determined characteristics based on the evaluation of the load value oscillation amplitude in the final portion of the curve may be proposed for detecting the moment of failure initiation in materials during mechanical tests.

In the paper, examination of a microchannel heat exchanger unsealed under service conditions is presented. Microscopic examinations revealed that the malfunction was caused by intergranular corrosion. Effect of microstructure on corrosion process in lamellae made of an Al–Mn alloy is discussed. It was found that occurrence of this corrosion was conduced by the phase β-Al6(Mn, Fe) present in microstructure of the lamellae. Precipitation of this phase is favoured by slow cooling after brazing and low concentration of silicon in the alloy. Low concentration of Si does not conduce possible transformation of Al6(Mn, Fe) to α-Al(FeMn)Si.

The main method for production of structural materials from metallic powders with addition or without addition of non-metallic powders is powder metallurgy (PM). This method is based on forming and sintering processes. The PM method consists of a small number of process steps and insignificant energy consumption, which allows to production of complex shape components, with great precision in dimensions and surface quality. Taking into account the above advantages, interest in sintered duplex stainless steels (SDSSs) is growing, which are characterized by two-phase microstructure consisting of ferrite and austenite. Such combination of properties makes the SDSS a very attractive material for numerous applications. As is well known, the chromium carbide coatings improve functional properties (e.g. hardness and wear resistance). The main purpose of this study was to examine the effect of chromium carbide coating on the properties of SDSSs. The multiphase sinters were prepared from two types of water-atomized steel powders: 316L and 409L. The technique of atmospheric plasma spraying (APS) was used to deposit Cr3C2–NiAl powder on SDSS surface. Additionally, it was carried out alloying the surface of the SDSS by gas tungsten arc welding (GTAW) process at current intensity 50 A. Light microscopy and scanning electron microscopy (SEM/EDS) were performed in order to determine the microstructure of SDSSs. The results of hardness and wear resistance measurements are also presented. The applied chromium carbide coatings cause hardening in SDSSs and modification of surface layer properties, such as coefficient of friction. Furthermore, the main assumption for this investigate was to analysis the microstructure and hardness of surface layer of SDSSs with different proportions of powders as a result the alloying process

Metallurgical slags are characterized by variable phase composition, which results from the technological process in which they were formed. The identification of the composition of slag, however, requires the application of a broad spectrum of complementary scientific methods. Besides the identification of phases using X-ray diffraction and using X-ray spectral microanalysis, one of the methods applied in mineralogical studies of slag is thermal analysis. Based on such analysis, it is not only possible to identify individual components of slags but also to analyse the transformations that occur in them under the influence of high temperature. The simultaneous application of DTA, TG and DTG measurement methods for converter slag has exhibited that the following processes occurred in the slags under the influence of variable temperature: dehydration, coal combustion, dehydroxylation, oxidation of iron, decarbonatization and phase transitions. The knowledge of the behaviour of slag under the influence of high temperature may provide valuable information in terms of its reuse.

This paper presents an attempt at the experimental evaluation of the behaviour of a glass-fiber reinforced epoxy laminate (10-layer) square plate, supported on a circular support and loaded centrally with a spherical indenter. The determination of the moment of the initiation of the material failure process under such loading conditions has been performed with use of photographic method. It was found that the performed test can be efficiently used to evaluate the properties of a material subjected to a compound stress state. However, due to high complexity of the issue mathematical calculation of stress is practically impossible. In order to determine the stress in the loaded laminate a numerical modelling should be applied. It is planned to be performed in separate study.

The crack tip opening displacement (CTOD), just like J integral, is a parameter characterising the fracture toughness of materials. The CTOD values are typically determined at subcritical crack initiation, δTi, or at 0.2 mm subcritical crack extension, δTC. The procedure for measuring δTC is described in detail in ASTM 1820. Measuring δTi is far more complicated and requires specialised apparatus and trained operators. The aim of this study was to assess the capability of different methods used for determining the value of δTi. The results from the experiments were compared with those from numerical calculations, obtaining good agreement between δTi data determined by the methods applied. The CTOD was measured on SENB (single-edge-notch-bend) specimens made of S355JR steel subjected to laboratory based heat treatment. The tests were performed at temperature in the range –80°C to 20°C, which allowed assessing the impact of reduced temperature on the δTi level.

This paper presents the current state of knowledge and characterises the orthodontic brackets currently available on the market. In recent years, new trends have been observed in materials engineering of these products. They arise as a result of the changing standards of treatment and increasing patient expectations and awareness in terms of aesthetics and safety of treatment. This has led to attempts to replace the metal alloys hitherto used for producing orthodontic brackets (stainless steel) with materials of higher translucency, biocompatibility and functional features (incl. anti-microbiological properties). These features should be accompanied by unchanged mechanical properties (strength, brittleness, elasticity, roughness).

COT (compression with oscillatory torsion) is a simple process that has the ability to deform bulk metallic samples. Performed investigations show that this method of deformation leads to grain refinement of Cu-Cr and Cu-Fe alloys. The grain size obtained via the dislocation subdivision mechanism associated with generation of non-equilibrum grain boundaries is in the UFG range. Large fraction of grain boundaries have low angles of misorientation. The limitation of the grain refinement and creation of low angles boundaries can be attributed to the extensive dynamic recovery. However, recrystallization process and deformation twinning plays a crucial role in grain refinement resulting in grain refinement to the nanoscale. The present overview shows that many structural elements accompanying formation UGF structure influence on understanding of the microstructure-properties relationship in these materials.

At present, there is a growing demand of the aviation industry on the parts prepared from light alloys which are characterised with sufficient stiffness and resistance. The technology of plastic deformation of magnesium alloys is a huge challenge. Due to the low plasticity of those materials in room temperature the parameters of the process of plastic working must be a satisfying compromise between the cost and the quality of the products. Due to those facts, alternative methods of plastic deformation of magnesium alloys need to be found. Particularly promising results in terms of the improvement in the susceptibility to plastic deformation are brought by new ultra-light magnesium alloys containing lithium. With the introduction of lithium, the density of which is 0.535 g/cm3, into the chemical composition of alloy, a further decrease of weight of alloy is achieved but at the same time the resistance of the material decreases. The article presents the results of tests of plastic deformation of Mg–Li–RE magnesium alloys. Alloys for extrusion process were achieved with the method of vacuum melting and casting to graphite moulds. The materials for tests were cast slabs from magnesium alloys with symbols LAE442. Before the process of deformation the castings were subject to homogenization. The tests of extrusion were conducted in complex state of deformation with using KOBO method. An assessment was performed of the influence of deformation process parameters on the microstructure of tested alloy. An analysis of microstructure was conducted both in initial condition and condition after plastic deformation with the use of techniques of light and scanning transmission electron microscopy.

In the article, the problem of infiltration of open-celled carbon foams by magnesium of technical purity and three cast magnesium alloys, AZ31, RZ5 and ZRE1, has been analysed. This issue is important due to a potential application of open-celled carbon foams (Cof) as a component in magnesium matrix composites. In the experiments, glassy carbon foams of porosity 20, 45 and 80 ppi were applied and the pressureless infiltration effects at 700°C in air atmosphere with proper flux protection as well as in argon atmosphere were studied. The macrostructure of the samples formed from component couples was characterized and the microstructure was examined with the LM and SEM methods. The obtained results confirm most of the literature data focused on the measurements of the carbon wettability by magnesium and indicate that spontaneous infiltration of carbon foams by magnesium is an ineffective and external force, i.e. a positive threshold pressure will be necessary in order to fabricate the composite.

The paper shows the results of the study into the effectiveness of structural laminate joining solutions by conducting comparative shear strength tests of adhesive and riveted joints of GFRP laminate components. In addition, the work shows selected surface roughness and texture parameters, a detailed analysis of failure forces measured in tensile test as well as analysis of failure modes of combined specimens. The theoretical and experimental sections of this paper describe the riveted and adhesive joints of the laminate substrates, and have led to several important conclusions in analysis of force and failure for two joint formations.

The article present results of microstructural investigation of so called composite type of thermal barrier coating of Sm2Zr2O7 + 8YSZ type deposited by air plasma spraying process with powders mass ratio 50/50, 25/75 and 75/25, respectively. For comparison standard 8YSZ coating was deposited as well. The internal structure quality assessment and surface topography characterization of obtained TBC`s were carried out. The ceramic layers were analysed for phase composition and residual stress. The coatings’ thickness was measured and vertical porosity was quantitatively and qualitatively characterized. Also the crystallite size of both samarium zirconate and yttria stabilized zirconia was evaluated. The obtained results were used for adjusted value of thermal conductivity calculation on the basis of results obtained from thermal diffusivity measurements at temperature between 20 and 1100°C.

The paper presents the test results obtained for fatigue crack growth in Ti-2.5Cu alloy subjected to bending in notched specimens. The tested specimens were subjected to various variants of heat treatment. The tests were performed at the fatigue test stand MZGS-100 under loading frequency 28.4 Hz. The study was conducted for a constant amplitude of moment Ma = 11.2 N∙m and different values of stress ratio R = –1 and 0. Influence of the microstructure on the crack paths in plane specimens was observed. The propagation of the main crack in the two-phase structure takes place both transcrystallinely through α phase grains and through the boundaries of the grains in metastable phase precipitation areas, whereas the propagation of the side cracks takes place along the precipitates of the coniferous phase. In the material after supersaturation and ageing at a temperature of 415°C, after Nf = 12 000 cycles (R = 0), no side cracks were observed, and the main crack develops in both phases that form the microstructure shown in Figure 10. A different fracture mechanism occurs for the material after supersaturation and ageing (Nf = 11 000 cycles) at a temperature of 760°C. In this case, an irregular path of the main crack is observed, whose direction in the micro-areas is determined by the precipitates of the intermetallic phase (Fig. 11). From the beginning of the main crack and along its entire length, numerous side cracks develop that are over 150 μm in length. The components of the structure that facilitate the propagation of cracks and determine their direction are clusters of Ti2Cu precipitates on the boundaries of α phase. In case of this alloy, the impact of the mean stress value during cyclic testing decreases fatigue life considerably.

Severe plastic deformation processes are one of the most promising methods for mechanical properties improvement through the grain refinement and strain accumulation. In the recent years, there is considerable interest in the application of the Equal Channel Angular Pressing method that is an effective tool for attaining ultrafine grain sizes in polycrystalline materials. A significant advantage of this method in comparison to conventional metalworking processes, such as extrusion and rolling, is that very high strains may be attained without any change in the cross-sectional dimensions of the sample. However, metalworking process of aluminium alloys may be complicated because of the alloying additions. It is known that aluminum–magnesium alloys are hardly deformable because the addition of Mg decreases workability. Thus there is a need to investigate the effect of the combination of heat treatment with SPD to simultaneously increase the workability and mechanical properties through the grain refinement. The research aimed to study the microstructure evolution of the AlMg5 alloy subjected to the heat treatment, ECAP and post-ECAP annealing. Microhardness measurements and tensile tests were undertaken to determine the mechanical properties of the AlMg5 alloy in different states. The results obtained show the relationship between the microstructure and the mechanical properties of the material. Key words: aluminum, SPD, ECAP, structure.

Chromium has been used for decades for the production of relatively thick, hard, wear resistant coatings in a wide range of industries - including the automotive and aircraft industry. Whilst traditional hard chromium finished coatings have no known health hazards, the chemicals, used in the process of application, comprise hexavalent chromium compounds (Cr6+ ions) and chromium in this state is extremely toxic. Due to the European directive on chemicals (REACH), hard chromium coatings, produced from highly toxic and carcinogenic baths, must be replaced by "green" solutions. In certain applications, the coatings obtained by PVD method can be the alternative to hard chromium electroplating where superior wear resistance to that of hard chromium electroplate is required - especially if a thin coating is suitable. Among PVD coatings, the chrome nitride coatings have demonstrated to possess excellent wear resistance properties. In this article was presented a fragment of research on this subject, carried out as part of an international research project CORNET, whose aim was to develop technologies of anti-wear and anti-corrosion coatings as replacements for hard chromium and cadmium coatings for applications in the aerospace and automotive industries. In particular, the article contains a description of the investigation of the mechanical properties of monolayer, gradient and multi-module coatings on CrN(C) base deposited with use of the cathodic arc evaporation CAE-PVD method on nitrided steel 42CrMo4 and additionally in the case of gradient and multi-module coatings on substrates of HS6-5-2 steel. The investigation includes the adhesion analysis by scratch test and by the Rockwell C indentation test (VDI - Verein Deutscher Ingenieure indentation test) tribomechanical analysis by pin-on-disc, measurement of friction coefficient and nanoindentation tests.

The paper presents results of a numerical analysis focused on an identification of mechanical properties of an element created using Fused Deposition Modelling additive manufacturing technique (FDM). There are presented a description of technology of the 3D printing, numerical model created by using finite element method (FEM), as well as some problems referred to estimation of the mechanical properties of the printout. The main point of the research was a study of relationship between properties of the rectangular infill structure (described in the micro scale) and the global values of selected mechanical properties of the part (described in macro scale). The numerical models of infill was created by applying the ABAQUS 6.12-1 software. The scope of the study involved tests performed in linear elastic limit of the material behaviour by applying uniaxial compressive load and two types of boundary conditions. Also, three alternative methods for identification of mechanical properties of the infill structures were presented. The results of the study of relationship between the density of infill structure and the Young’s modulus of the printout were presented and discussed.

AISI 316L-hydroxyapatite biomaterials were produced by the conventional powder metallurgy technology. In the case of materials such as these, proper and long-term functioning in the aggressive environment of body fluids is very important. Therefore, the purpose of this study was to determine the effect of hydroxyapatite content and sintering temperature on the properties including sintered density, open porosity, and in particular corrosion resistance of AISI 316L-hydroxyapatite biomaterials in Ringer’s solution. The measurement of sintered density and open porosity of studied materials was carried out by the water-displacement method. The corrosion behaviour was studied by open circuit potential measurement and potentiodynamic polarization method. It was stated that the properties of studied biomaterials are dependent on chemical composition of powders mixture and sintering temperature. The results showed that higher sintering temperature ensured to obtain lower values of corrosion current density and corrosion rate, and higher value of polarization resistance. The addition of 5 wt % hydroxyapatite provided to a significant improvement of corrosion resistance in Ringer’s solution in comparison to AISI 316L steel, while a slight decrease in corrosion resistance was observed for AISI 316L-10 wt % hydroxyapatite biomaterials. Passivation ability and better corrosion resistance indicate that sintered at 1240°C AISI 316L–5 wt % hydrohyapatite biomaterials is more appropriate for long-term functioning implants than AISI 316L steel. This biomaterial possessed good densification and the best corrosion resistance among all studied materials, as evidenced by the lowest corrosion current density and corrosion rate combined with the highest polarization resistance.

The hypereutectoid alloys are the commonly used for the tool manufacturing. The high carbon content prevent the high hardenability and presence of the secondary cementite precipitation in microstructure. High hardness of such materials provide the good wear resistance required for tool materials. New hypereutectoid alloys designed for the investigations of secondary cementite precipitations influence on wear resistance have been investigated. Materials were prepared by the use of the ArcMelter furnace. After the plastic deformation materials were annealed at 700°C by 12 h to homogenize the microstructure. After the annealing the calorymetry and dilatometry research were performed. The following research allow authors to state that the increase of the carbon content resulted in the change of ACCM temperature. To obtain the most similar properties of the matrix investigated materials were alloyed by the addition of Cr and Mn. It was confirmed by the same temperature range of the eutectoid transformation for each material. Additionally the influence of Mn and Cr on cementite dissolution process was observed.

Traditional metallography combined with microhardness testing and chemical composition analysis were used to understand the premature deterioration of steel pipes used in water distribution systems, namely, a zinc-coated steel pipe used in potable water distribution systems and a black steel pipe used for sprinkler fire protection systems. The investigated pipes were found to fail after a short service time, with numerous water leaks in a period of less than two years of service. This study shows that the failure was mainly a consequence of the Sandelin phenomenon caused by inadequate metallurgical quality, i.e. the silicon content was too high in the zinc-coated steel pipe, and an improper seam welding procedure in the case of the black steel pipes.