Adhesion and corrosion resistance properties of coatings obtained from modified low-molecular-weight polystyrenes

In this study, as a continuation of our previous studies, chemical modification of low-molecular-weight polystyrenes (PSs) was carried out with various functional group modifiers: epichlorohydrin (ECH), maleic anhydride (MA) and acetic anhydride (AA), in a single stage using a cationic catalyst. It was determined that the amounts of the functional groups bound to the structure of the polymer depended on the molecular weight of the polymer used, and more functional groups were bound to the lower-molecular-weight PSs. It was found that the coating properties (adhesion properties and resistance to aggressive conditions) of the functional group containing PS to the metal surface depended on the structure and the amount of the functional groups bound to the aromatic ring of the polymer. In addition, it was observed that the PS modified with MA and ECH having carboxyl- and epoxy-groups in their aromatic rings had higher adhesion, as well as higher corrosion resistance properties. Various functional groups bound to the aromatic ring of the polystyrene and their amounts were determined by spectral and chemical analysis methods.     

Effect of annealing on the cohesion,adhesion, and tribological behavior of amorphous silicon-containing diamond-like carbon (Si-DLC) coatings on steel

Amorphous silicon-containing diamond-like carbon (Si-DLC) coatings were deposited by Ar+ ion beam-assisted physical vapor deposition of tetraphenyl-tetramethyl-trisiloxane (704 Dow Corning diffusion pump oil) on AISI 4340 low alloy and 440° C high alloy steel specimens, as well as on thin wafers of the same compositions, in order to evaluate residual stresses within the coatings. During annealing in an argon atmosphere at 200°C for up to 30 min, the residual compressive stress, attributed to hydrogen entrapment during deposition, gradually changed to tensile due to loss of hydrogen, and the rate of stress increase decreased with increasing annealing time. The cohesion and adhesion failure loads of the coatings decreased with annealing time, as did the friction coefficient between the coating and a diamond stylus. The specific wear rate, measured by pin-on-disk tribometry, increased with annealing time. These properties are affected not only by the change in residual stress state during annealing, but most likely also by devitrification and the accompanying grain growth. If these effects are neglected, then the properties may be correlated directly with residual stresses in the coating.     

Liquid crystalline adhesives for polypropylene joints

This study was devoted to the investigation of the adhesion of epoxy resins to polypropylene adherends. In particular, the study was carried out as follows: synthesis of both a liquid crystalline (LC) and a bisphenol-A-based resin, their characterization and their further evaluation as adhesives for polypropylene adherends. This was done in order to evaluate the difference between an LC epoxy resin and an isotropic one in adhesive applications. The adherends chosen were neat polypropylene (PP) and polypropylene reinforced with 20 and 40 wt% talc (PP20 and PP40, respectively). The effect of two different pre-treatments (simple degreasing and acid etching) on the polypropylene adherends was also evaluated. It was shown that the adhesion strength of the liquid crystalline adhesive was higher compared to that of the isotropic one. The higher adhesion was related to the extra ductility demonstrated by the LC epoxy resin, which was due to its particular microstructure. Moreover, the acid etching pre-treatment performed on polypropylene adherends prior to bonding improved the adhesion at the interface with the resin. The increased stiffness of the adherends due to the presence of talc turned out to be beneficial to obtain more resistant joints.     

Melting and solidification of TiNi alloys by cold crucible levitation method and evaluation of their characteristics

Abstract

The addition of Re, Fe and Cr into Ti–50 mol.-%Ni has been carried out to improve the oxidation and mechanical properties. The mono phase consisting of TiNi with the B2 type structure was identified in micro-alloyed materials proposed on the basis of the d-electrons concept. Experimentally, TiNi alloys were melted and solidified by the cold crucible levitation melting (CCLM) method. The TiNi–(Cr, Fe, Re) alloys with high purity and without contamination from a crucible were prepared, and the homogeneous microstructure was achieved by the diffusion mixing effect of CCLM even in the as-cast alloys which contained Re and Cr with higher melting temperatures and different specific gravities. The transformation from austenite to martensite phases occurred in all alloys below or above room temperature. Some alloys had the ability of shape memory even at room temperature. Ternary alloys showed a higher flow stress level compared with the binary TiNi alloy. On the other hand, the oxidation at 1273 K was promoted by the formation of titanium oxides (TiO₂) on the alloy surfaces. The oxidation resistance was improved by the formation of the continuous Cr₂O₃ film in TiNi–Cr alloys. The alloying effects by ternary elements (Re, Fe, Cr) in the intermetallic TiNi as well as metallic materials were explained well using two parameters used in the d-electrons concept.     

Mechanical properties and wear behaviour of PM aluminium composite reinforced with (Fe3Al) particles

Abstract

Mechanical properties and wear behaviour of an aluminium matrix composite reinforced with Fe₃Al intermetallics have been studied. A 2014 alloy manufactured through mechanical alloying was used as the matrix. Three different Fe₃Al intermetallics have been used as reinforcement, also manufactured through mechanical alloying. The difference between them was the different mechanical alloying times (5 and 20 h were used) and the possibility of carrying out a heat treatment at 1000°C (on the 20 h milled intermetallic) before admixing to the aluminium matrix. The processing of these composite materials included mixing and cold compacting (conventional powder metallurgy) followed by hot extrusion (without caning and degassing). The effect of a T6 heat treatment was also evaluated. The influence of intermetallic additions on the mechanical properties (hardness and tensile strength) and wear behaviour (pin on disk test) was established. All intermetallics showed a good link with the matrix, and high reactivity with it during the heat treatment, as the microstructural study supports.     

New experience in field of application of corrosion resistance protection in flue gas desulphurisation plant absorbers

Abstract

Absorbers form the main part of the flue gas desulphurisation plants for 360 MW units at the Belchatow Power Station in Poland. The plant working cycle and service life are dependent on the grades of the corrosion resistance, protection materials used as an absorber lining in individual zones. The objective of manufacturers activities in this field has been to extend the service life of the flue gas desulphurisation plant. This has been implemented by testing 'wallpapering' technology in the absorber cylindrical part, using plate sheets of Hastelloy nickel alloys, 0·5 to 1·6 mm in diameter. Experiments involving Hastelloy nickel alloys, grades C-22 and C-2000, among others, were used to evaluation the resistance of the base material, 'wallpaper' plate sheet, welded joints and heat affected zones (HAZ) towards corrosion. The corrosion tests were executed for three different conditions of corrosive environment: (a) actual boiler outlet environment: chemical composition of boiler outlet flue gases, with addition of 10 wt-%K₂SO₄; a testing temperature of 70°C; and a testing time of up to 1000 h; (b) actual boiler outlet environment: chemical composition of boiler outlet flue gases, with addition of 6 wt-%K₂SO₄ and 4 wt-%NaCl; a testing temperature of 70°C; and a testing time of up to 1000 h; (c) simulated waste incineration environment, produced during thermal utilisation of wastes with the following chemical composition: N₂–9%O₂–0·08%SO₂–0·2%HCl; testing temperatures of 450 and 600°C; and a testing time was up to 1150 h. For the purpose of comparison, corrosion resistance tests were carried out on boiler steel types T22, E911, HCM12 and TP347H. This paper includes results of the evaluation of welded joints structure and HAZ, joint corrosion resistance characteristics, corrosion product test results, as well as requirements and recommendations with regard to fabrication of welded joints, the preparation degree of lining plate join surfaces, and requirements in field of weld joints.     

Two body type abrasion wear behaviour in hypoeutectic 16%Cr cast irons with Mo

Abstract

Hypoeutectic 16%Cr cast irons, both Mo free and 1–3%Mo containing specimens were prepared to investigate their abrasion wear behaviour. Annealed specimens were hardened at 1323 K and then tempered at three temperatures from 673 to 873 K for 7·2 ks, the temperature giving the maximum hardness (H_Tmax) and the lower and higher temperature, (L-H_Tmax, H-H_Tmax). The abrasion wear behaviour was investigated using a two body type Suga abrasion wear tester. A linear relation was obtained between wear loss and wear distance. The highest wear resistance or the lowest wear rate (R _W) was obtained in H _Tmax specimens except for the Mo free specimen. The lowest wear resistance or the highest R _W was obtained in H-H_Tmax specimens. The R _W was decreased with an increase in macrohardness. The lowest R _W appeared around 25% retained austenite (V _γ ). The R _W was decreased with an increase of Mo content, and the V _γ value at the minimum R _W shifted to the high V _γ side.     

24—A CRITICAL COMPARISON OF EMPIRICAL TESTS OF THE EXTENSIONAL RESILIENCE OF TEXTILE FIBRES: PART III: COMPARISON BETWEEN RECOVERY TESTS AND THE PERFORMANCE OF CARPET-LIKE CONSTRUCTIONS

A series of polypropylene-fibre continuous-filament yarns was used to manufacture a set of simplified carpet-like structures. Recovery and wear tests on these samples are described and the results compared with those of single-filament recovery tests discussed in Parts I and II of this series. It is concluded that single-filament testing can indicate very poor or very good yarns, although unconsidered effects dominate the performance of intermediate samples.     

Fibre orientation structures and their effect on crack resistance of injection moulded transverse ribbed plate

Abstract

An extensive study of the fibre orientation structures developed in a transverse ribbed plate during injection moulding, and the use of these structures to investigate the effect of local fibre orientation state on crack initiation resistance, is reported. The fibre orientation results for the ribbed plate, measured using large area image analysis system developed at Leeds University, showed that after an initial settling down period, the central core region, where the fibres are aligned perpendicular to the flow direction, decreased in size monotonically, with an associated monotonic increase in the outer shell regions, where the fibres are aligned preferentially along the injection direction. Interestingly, the level of orientation in the two regions remained almost constant: only the proportions of the two regions were found to change with flow length. Across the plate, close to the gate, the central core region was found to have a lens-like shape, while at the other end of the plate the core was thinner and also consistent in thickness across the sample width. The transverse rib was found to cause little disturbance to the fibre orientation of the base plate. The different proportions of the shell and core regions at different locations over the ribbed plate provided an ideal case to test the proposition of Friedrich that the crack resistance of a short fibre reinforced material depends on the number of fibres that are perpendicular to the crack tip. The impact test results gathered in this way confirmed this hypothesis of Friedrich.     

Comparative studies on wear behaviour between as cast AZ91 and Mg97Zn1Y2 magnesium alloys

Abstract

The wear behaviour of as cast magnesium alloys, Mg₉₇Zn₁Y₂ and AZ91, was investigated under dry conditions in load ranges of 20–380 and 20–240 N respectively, using a pin on disc wear testing machine. The microstructure, thermal stability and elevated temperature tensile properties were characterised by optical microscopy, X-ray diffraction, differential thermal analysis and tensile testing respectively. The wear behaviour can be divided into three successive phases in terms of surface temperature induced by frictional heat, i.e. ambient temperature to eutectic temperature or precipitate dissolution temperature, eutectic temperature or precipitate dissolution temperature to the liquidus temperature and above the liquidus temperature. The Mg₉₇Zn₁Y₂ alloy exhibited good wear resistance compared with the AZ91 alloy for applied loads in excess of 80 N, which has been explained in terms of thermal stability of the intermetallic phase and elevated temperature mechanical properties of the two materials tested, by surface temperature analysis and subsurface observation.