This paper presents the synergy of the effect of two surface engineering technologies—magnetron sputtering (MS-PVD) and atomic layer deposition (ALD) on the structure and properties of 316L steel. Recent studies indicate that PVD coatings, despite their thickness of a few micrometers, have many discontinuities and structural defects, which may lead to pitting corrosion after time. Applying an ALD layer to a PVD coating seals its structure and contributes to extending the service life of the coating. Investigations of the structure and morphology of the produced layers were carried out using a scanning electron microscope (SEM) and atomic force microscope (AFM). In addition, the structure of the coatings was investigated on the cross-section using a scanning-transmission electron microscope S/TEM. The tribological properties of the materials studied were determined by the ball-on-disc method. The corrosion resistance of the tested materials was determined by the electrochemical potentiodynamic method by recording the polarization curves of the anodes. Additional information about the electrochemical properties of the tested samples, including the quality, their tightness, and their resistivity, was obtained by electrochemical impedance spectroscopy (EIS). In addition, the main mechanisms of corrosion and tribological wear were determined by SEM observations after corrosion tests and after tribological tests. The study showed that the fabrication of hybrid layers by MS-PVD and ALD techniques allows obtaining coatings with electrochemical properties superior to those of layers fabricated by only one method.

In view of the need to increase the durability of working tools exposed to intense friction, this study analysed hybrid coatings (TiAlCN, AlTiCN, AlCrTiN, TiN, CrN) with a DLC (Diamond-Like Carbon) layer, deposited using PVD (Physical Vapour Deposition) methods (arc evaporation and magnetron sputtering). The structural characteristics of the coatings were determined using SEM (Scanning Electron Microscope) and AFM (Atomic Force Microscope) microscopy, as well as Raman spectroscopy, which confirmed the compact structure and amorphous nature of the DLC layer. Tribological tests were performed using a ball-on-disc test, revealing that DLC hybrid coatings significantly reduce the coefficient of friction (stabilisation in the range of 0.10 to 0.14 due to DLC graphitisation), limiting tool wear even under increased load. The SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscopy) microscopic examination revealed that the dominant wear mechanisms are abrasive and adhesive damage, and the AlCrTiN/DLC system is characterised by low wear and high adhesion (L_c = 10⁵ N), making it the optimal configuration for the given loads. Microhardness tests showed that high hardness does not always automatically translate into increased wear resistance (e.g., the AlTiCN coating with 4220 HV showed the highest wear), while coating systems with moderate hardness (TiAlCN/DLC, CrN/DLC) achieved very low wear values (~0.17 × 10⁻⁵ mm³/Nm), which highlights the importance of synergy between the hardness of the sublayer and the low friction of DLC in the design of protective coatings.

Background. Frictional resistance is an important parameter in orthodontics that influences the effectiveness of archwire-guided tooth movement. Since the consumption of dietary acids has increased considerably over the last 2 decades, there is a rationale for investigating the process of degradation of orthodontic materials in an acidic environment and its effect on clinical efficiency. Objective. The aim of this study was to evaluate the effect of simulated erosive conditions on the frictional behavior between the brackets of 3 different materials and 3 different wire alloys. Material and methods. Three types of twin orthodontic brackets (stainless steel (SS), monocrystalline ceramic and titanium) and 3 types of archwires of the same dimension (SS, nickel-titanium (Ni-Ti) and beta-titanium (titanium-molybdenum alloy-TMA) were tested in 9 different combinations under simulated erosive and non-erosive conditions (18 groups, n = 10). Bracket-wire specimens in the erosive-condition groups were subjected to a pH cycling regimen with 1% citric acid and artificial saliva for 5 consecutive days. Bracket-wire specimens from the non-erosive-condition groups were incubated only in artificial saliva for 5 days. Static and kinetic friction were determined by measuring the force needed to move the wire through the bracket. A three-way analysis of variance and pairwise comparisons with the Student-Newman-Keuls test were performed. Results. Irrespective of the conditions, SS brackets with SS wire demonstrated significantly lower mean static and kinetic frictional resistance than other bracket-wire combinations (p < 0.01). Ceramic and titanium brackets generated high frictional forces with all 3 types of wire tested. Erosive conditions did not significantly influence static and kinetic frictional resistance in all bracket-wire groups. Conclusions. Erosive conditions do not affect the frictional behavior of SS, Ni-Ti and TMA orthodontic archwires at a clinically significant level.

Investigations carried out referred to obtaining material based on the high-speed steel and non-alloy steel. The conventional powder metallurgy method was used for manufacturing these materials, consisting in compacting the powder in the closed die and sintering it next, the isostatic pressing method, and the modern pressureless forming powder metallurgy. Forming methods were developed during the investigations for high-speed and non-alloy steel powders, making it possible to obtain materials with three layers in their structure. Investigations included determining the sintering conditions, and especially the temperature and treatment cycle, as well as examining the selected mechanical properties. It was found out, basing on the comparison of structures and properties of test pieces made with the pressureless forming method, as well as with the isostatic pressing and pressing in the closed die, with further sintering, that in structures of all examined test pieces in the sintered state fine carbides occurred distributed homogeneously in the high-speed steel layer. It was noticed, that increase of the sintering temperature, regardless of the manufacturing method, results in the uncontrolled growth and coagulation of the primary carbides and melting up to forming of eutectics in layers consisting of the high-speed steel. It was found out basing on the microhardness tests that hardness of test pieces both those pressureless formed, compacted in the closed die, and isostatically cold pressed and sintered grows along with the sintering temperature. It was also noted that the sintering temperature range is bigger in case of the pressureless formed materials.

Salivamoistened enamel. Design/methodology/approach: One hundred twenty stainless steel brackets were bonded to human mandibular third molars with six materials: Enlight LC® (Ormco Corp), Grengloo® (Ormco Corp), Light Bond® (Reliance Orthodontic Products), Charisma® (Heraeus Kulzer), SmartBond® (Gestenco), and Transbond XT® with MIP® primer (3M Unitek). One half of the specimens in each group (n=10) was bonded to dry enamel, while the other half to saliva-moistened enamel. Bond strength testing was performed with a wire loop loading technique after 30-min incubation in artificial saliva. Failure mode was evaluated using adhesive remaining index (ARI). Findings: No significant differences in bond strength to dry enamel were noted for all composite materials (p>0.05). SmartBond exhibited significantly greater bond strength to moistened enamel (7.10 ± 1.47 MPa) and comparable with other composite materials to dry enamel. Composite materials demonstrated significantly reduced bond strength to saliva-moistened enamel (p<0.001), except for Transbond MIP, whose bond strength was not significantly decreased by saliva contamination (p=0.089). There was not statistically significant difference between bond strength of SmartBond and Transbond to saliva contaminated enamel. A higher incidence of cohesive failures was noted for all materials. Research limitations/implications: Composite light-cured materials provide adequate bond strength to dry enamel. Cyanoacrylate adhesive provides sufficient bond strength only under moist conditions. Transbond XT+MIP has sufficient bond strength to either dry or saliva-moistened enamel. Practical implications: The study evaluated the bonding strength of orthodontic brackets, which is a critical parameter in orthodontics, especially in situations that do not allow for proper isolation from saliva, such as bonding to impacted teeth following surgical exposure. Originality/value: Bond strengths evaluated with loop loading technique in different study environments would help the orthodontist to choose the most effective adhesive for the specific clinical situation.

Fabrication, Structure, Properties and Application of Gradient Sintered Carbide-Steels with HS6-5-2 Matrix | InTechOpen, Published on: 2017-03-29. Authors: Leszek Adam Dobrzański and Anna Kloc-Ptaszna