PVD Coatings Influence (TiCN, BCN and CrAlN) on the Fatigue Life Behavior of AISI 1045 Steel for Automotive Applications

This current work evaluated the influence of Titanium Carbo-nitride (TiCN), Chromium Aluminum Nitride (CrAlN) and Boron Carbo-nitride (BCN) coatings deposited on AISI 1045 steel and its behavior in fatigue life. Suitable deposition parameters were established for the coatings to show high hardness onto the substrate, appropriate deposition time for polycrystalline growth and desired stoichiometry, as well as a stable layer thickness of ~ 3 µm. The physical and chemical properties of the coatings obtained were established by X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS) and nanoindentation; the scanning electron microscopy (SEM) was used for the analysis of the fracture surfaces of the samples subjected to fatigue. The analysis of the fatigue behavior of the uncoated and coated substrates were performed under rotary bending conditions applying maximum alternating stresses in the interval of 55–70% of the ultimate strength value, i.e. from 479 to 610 MPa, respectively; the test was performed at room temperature. The study of the results established that the fatigue resistance properties increased for the three types of coated samples, TiCN, BCN and CrAlN, with values of 9.6%, 4.2% and 3.9%, respectively, calculated for 1x106 cycles. The highest value in fatigue life improvement corresponded to the TiCN coating, followed by BCN. This can be associated to the increase hardness present in the TiCN layer; this improved the mechanical properties of the coating. The examination of the fracture surfaces carried out in the tested samples (coated and uncoated), clearly demonstrate that the cracks produced by fatigue started in the surface of the coating and later propagated to the substrate. The mechanicals and fatigue results found in these ternary coatings deposited on AISI 1045 steel open a possibility of future applications in mechanical devices e.g. automotive applications that require high fatigue demands in service conditions.

Surface Characterization and Assessment of Biofilm Formation on Two Titanium-Based Implant Coating Materials

Implant-related oral diseases such as peri-implantitis and peri-mucositis are largely initiated by bacterial colonization on artificial implant surfaces. Therefore, implant and abutment material characteristics that minimize bacterial attachment and subsequent biofilm formation are important factors in reducing the risk of infection-related implant failure. This study compares the properties of two different titanium-based implant coating materials, titanium nitride (TiN) and titanium carbon nitride (TiCN). Surface hydrophilicity/ hydrophobicity and roughness were evaluated via contact angle measurements and surface profiling with white light interferometry, respectively. TiN-coated surfaces were hydrophobic according to its contact angle higher than 72.7°, whereas TiCN-coated surfaces were hydrophilic with its contact angle of 53.6°. The average roughness (Ra) was greater for TiCN than TiN with the root mean square roughness (Rq) being significantly higher. These findings are in contrast to the common understanding for titanium-based materials that surface roughness and hydrophobicity are positively correlated. A well-established saliva-based oral microbial biofilm model was employed to compare bacterial attachment and biofilm formation on TiN and TiCN. Growth conditions included relevant host components such as blood as well as the presence or absence of dietary carbohydrates. The accumulated biomass was measured by crystal violet staining and the bacterial community profiles of the attached biofilms were determined via 16S rRNA gene microbiome sequencing at different time points over a 7-day period. At all time points, TiCN showed significantly less bacterial attachment and biofilm formation compared to TiN. This implied the importance of the hydrophilic state over surface roughness as parameter for the prevention of oral microbial attachment. Although, the biofilm community composition was very similar on both materials, environmental growth conditions resulted in significantly different bacterial profiles independent of the surface. In conclusion, TiCN coating produced a unique titanium surface which is rougher but more hydrophilic. TiCN-coated surfaces exhibited reduced bacterial attachment and biofilm formation in comparison to TiN coating. This coating technique can be further explored to improve implant and abutment success.

Analysis of Different Complex Multilayer PACVD Coatings on Nanostructured WC-Co Cemented Carbide

The development of cemented carbides nowadays is aimed at the application and sintering of ultrafine and nano-sized powders for the production of a variety of components where excellent mechanical properties and high wear resistance are required for use in high temperature and corrosive environment conditions. The most efficient way of increasing the tribological properties along with achieving high corrosion resistance is coating. Using surface processes (modification and/or coating), it is possible to form a surface layer/base material system with properties that can meet modern expectations with acceptable production costs. Three coating systems were developed on WC cemented carbides substrate with the addition of 10 wt.% Co using the plasma-assisted chemical vapor deposition (PACVD) method: single-layer TiN coating, harder multilayer gradient TiCN coating composed of TiN and TiCN layers, and the hardest multilayer TiBN coating composed of TiN and TiB2. Physical and mechanical properties of coated and uncoated samples were investigated by means of quantitative depth profile (QDP) analysis, nanoindentation, surface layer characterization (XRD analysis), and coating adhesion evaluation using the scratch test. The results confirm the possibility of obtaining nanostructured cemented carbides of homogeneous structure without structural defects such as eta phase or unbound carbon providing increase in hardness and fracture toughness. The lowest adhesion was detected for the single-layer TiN coating, while coatings with a complex architecture (TiCN, TiBN) showed improved adhesion.

TiCN coating tribology for the circular economy of textile industries

The circular economy is still a hypothetical field in Europe. Different shredding and manufacturing machinery parts in textile industries are presumed to enhance product quality and performance. The quality and performance of recycled textile products play a vital role in the development of textile recycling technologies. The quality is principally associated with the mechanical and tribological properties of machinery parts. In this article, TiCN Coating is used to determine the coefficient of friction of post-consumer cotton fabric. The scanning electron microscope, optical and mechanical profilometer, and tribometer were used for surface and tribological evaluations. The TiCN coating was found smooth and homogeneous. The average coating surface roughness parameters Rmax, Rz, Rp were 0.24 µm, 0.21 µm, and 0.20 µm, respectively. The dynamic coefficient of friction values was found 0.38 to 0.30 in the warp and 0.33 to 0.28 in weft directions. The increase in sliding distance is used for industrial applications and evaluations. The increase in distance deformed and fractured cotton fabric surface. The coefficient of friction and deformation becomes constant after 40 m of sliding distance. Based on coefficient of friction values, permanent deformation, fracture, and morphologies evaluations TiCN coatings could be used operationally for surface modification of textile machinery parts. The surface modification of textile machinery parts with TiCN coating can enhance the quality and performance of textile products.

Corrosion and Electrochemical Impedance Spectroscopy of Thin TiALN and TiCN PVD Coatings for Protection of Ballast Water Screen Filters

The electrochemical impedance spectroscopy (EIS) and corrosion behaviour of physical vapour deposited (PVD) TiAlN and TiCN coatings of 50 µm mesh shaped AISI 316 stainless steel were estimated under simulated marine conditions (3.5 wt. % NaCl solution). The coatings were prepared by creating adhesive Cr-CrN interlayer with the thickness of about 0.3 µm. The obtained thicknesses of produced coatings were measured to be in a range between 2 and 3.5 µm. The presence of protective coatings leads to corrosion potential (Ecorr ) shifting to more positive values as compared to the bare stainless steel. This effect indicates higher protection efficiency of coated steel under marine conditions. The protective behaviour of produced coating leads to the decreased corrosion current density (jcorr ) by indicating up to 40-fold higher polarization resistance as compared to resistance of the naturally formed oxide layer over the stainless steel. The Nyquist and Bode plots were obtained with the help of EIS measurements by applying alternating potential amplitude of 10 mV on observed Ecorr . The obtained plots were fitted by appropriate equivalent circuits to calculate pore resistance, charge transfer resistance and capacitance. The present study reveals that pore resistance was the highest in the case of TiCN coating (Rpore =3.22 kΩ·cm2). The increase in duration of the immersion up to 24 h leads to change in the capacitive behaviour of the coatings caused by the penetration of the aqueous solution into pore system of TiCN coating with low wettability and surface passivation of reactive TiAlN coating. The presence of defects was confirmed by examining the obtained samples with the help of the scanning electron microscope.

The Effect of Stirring Tool Surface Condition on Wear Characteristics in Friction Stir Welding (FSW) Process

Stirring tool is one of the important factor that contribute to the successful of Friction Stir Welding (FSW). Role of tool, is to heat the welding zone and stir the material along the process. Many studies have been conducted by other researchers to improve the performance of stirring tool. Similar to this work, it is aimed to investigate and analyze the effect of stirring tool surface condition on wear characteristics in friction stir welding process. Four tools have been fabricated with pre-determined surface condition. Tool 1: H13 without heat treatment and without coating. Tool 2: H13 with heat treatment only. Tool 3: H13 with TiCN coating only and Tool 4: H13 with heat treatment and with TiCN coating. Friction stir welding was performed to test and verify the performance of fabricated tools. Process parameter used are 1270 RPM for rotating speed while 218 mm/min for welding speed. From the result, Tool 4 performed better in terms of physical wear as well as wear rate.

Optimization of tool design parameters for thread tapping process of Ti-6Al-4V

Thread tapping is one of the most important machining processes. Although thread tapping is a usual process and has been used for decades, the process still needs improvement for promising materials such as titanium alloys to increase the performance of the process. Titanium alloys are known as difficult-to-cut materials due to their low heat conductivity and elastic modulus. The aim of the work presented in this paper is to optimize the tapping tool primary design parameters for Ti-6Al-4V. The most influential tool design parameters on the process were selected as the rake angle, helical flute angle, chamfer angle, and tool coating. Optimization of the tool design parameters was made by considering the results of the experimental work. Two levels of each parameter were chosen. Taguchi L8 orthogonal array was used as the design of experiment. Tapping tool temperature and tapping torque were determined as the process outputs. According to the results, the optimized tool design parameters were found as 6° rake angle, 12° helical flute angle, 14° chamfer angle, and TiCN coating.