Effective Surface Treatment Research Articles

Evaluation of wear and corrosion resistance in acidic and chloride solutions of Cathodic Arc PVD chromium nitride coatings on untreated and plasma nitrided AISI 4140 steel

Chromium nitride ceramic like coatings are well known for their hardness and wear resistance, especially under severe conditions. When deposited on mild steel, nitriding is required for such applications to create a gradient hardness profile and improve the coating adhesion and the system's mechanical properties. Corrosion resistance is also necessary since these chromium coatings are recommended for applications in the plastic mould and injection industry. Therefore, in this work, the combination of a nitriding without white layer pretreatment and CrN coating was studied in a chloride and an acidic electrolyte, to asses if the diffusion layer also plays an important role as a corrosion protection treatment. Coating microstructure, adhesion to both nitrided and non-nitrided steel, wear resistance, and corrosion resistance in chloride and acidic media were evaluated. For comparison, bare and nitrided steel were also examined. Results indicated an improvement in the adhesion for the duplex treatment (nitriding + CrN). The CrN coating demonstrated a considerably lower coefficient of friction and wear rate compared to both non-nitrided and nitrided steel. Regarding corrosion, the iron nitride layer provides some protection in chloride environments; however, in acidic media, only the CrN coating plays a protective role. In both media, localized attack occurred at sites where the coating had defects, such as pores or pinholes through which the electrolyte comes into contact with the substrate. The duplex treatment proved to be the most effective surface treatment for AISI 4140, achieving excellent tribological properties, good adhesion, and high corrosion resistance in both neutral chloride and acidic solutions.

Effective surface treatment for efficient and stable inverted inorganic CsPbI2Br perovskite solar cells

The interest in all-inorganic perovskite solar cells (PSCs) featuring a p-i-n structure is on the rise, attributed to their superior heat resistance and adaptability with tandem cell methods. However, their progress has been far from the regular structure owing to the comparatively low open circuit voltage (Voc). This research employs phenylethylammonium iodide, incorporating various side groups, as passivators to tackle the previously mentioned problems and investigate their effects on passivation. It is found that a reduction of trap-state density in perovskite film was accomplished due to the PEAI effective passivation effect by establishing coordination with the under-coordinated Pb2+ ions. Furthermore, there was an enhancement in the alignment of energy levels at the CsPbI2Br perovskite/PCBM junction, resulting in better charge extraction from the CsPbI2Br layer to the charge transport layer. As a result, an improved champion efficiency of 14.26 % with a Voc of 1.11 V, Jsc of 16.21 mA/cm2, and FF of 79.28 % was yielded for the PEAI treatment inverted CsPbI2Br device, compared with the 12.15 % efficiency of the control device. Superior device stability was exhibited for the optimal PEAI-treated devices without encapsulation. This research validates the significance of a side group on a surface passivation molecule to effectively passivate defects and optimize energy levels, especially for boosting Voc.

Efficient synthesis of durable superhydrophobic SiO2@PFDMS coatings on bamboo by liquid deposition

Fast-growing bamboo offers a sustainable alternative to meet the increasing demand for wood. However, its inherent hydrophilicity limits its performance, necessitating hydrophobic modifications to enhance longevity. In this study, 1 H,1 H,2 H,2 H- perfluorodecyltrimethoxysilane was used to anchor SiO2 nanoparticles onto bamboo surface, creating superhydrophobic coatings. The nanoparticles constructed a micro-/nano-rough structure on the bamboo surface, and fluorosilanes significantly reduced the surface energy of bamboo. The wettability, micro-morphology, chemical composition, and resistance to acid and alkali corrosion, mechanical abrasion, and UV aging of the superhydrophobic coatings were extensively investigated. The results demonstrated that the modified bamboo achieved a surface energy of 0.2±0.0 J/m2 and a water contact angle of 156.8±0.2°. Furthermore, the coating exhibited excellent chemical and physical stability. This straightforward and effective surface treatment method offers substantial potential for broadening bamboo's applications in outdoor environments.

Controllable Fabrication of Hydrophilic Surface Micro/Nanostructures of CFRP by Femtosecond Laser.

Carbon fiber reinforced polymer (CFRP), a highly engineered lightweight material with superior properties, is widely used in industrial fields, such as aerospace, automobile, and railway transportation, as well as medical implants and supercapacitor. This work presents an effective surface treatment method for the controllable fabrication of hydrophilic surface micro/nanostructures of CFRP through femtosecond laser processing. Selective removal of the epoxy resin and leaving the carbon fibers exposed are achieved when CFRP is weakly ablated by a femtosecond laser. The diameters and structures of the carbon fibers can be controlled by adjusting the laser processing parameters. Three-dimensional surface micro/nanostructures are processed when CFRP is strongly ablated by a femtosecond laser. Meanwhile, the transformation of the sp2 orbitals to sp3 orbitals of graphitic carbons of carbon fibers is induced by a femtosecond laser. Moreover, the investigation of surface roughness and wettability of femtosecond laser-processed CFRP indicates increased roughness and excellent hydrophilicity (a contact angle of 28.1°). This work reveals the effect of femtosecond laser processing on the regulation of the physicochemical properties of CFRP, which can be applicable to surface treatment and performance control of other fiber-resin composites. The excellent hydrophilicity will be conducive to the combination of CFRP with other materials or to reducing the friction resistance of CFRP used in medical implants.

Microstructure, mechanical and corrosion study of friction stir processed Inconel 625 additive layers deposited via wire arc direct energy deposition

This study explores the application of friction stir processing (FSP) as an effective post-deposition surface treatment technique for improving the mechanical and corrosion properties of wire arc direct energy deposited (WA-DED) Inconel 625 additive layers. The coarse and cube-oriented microstructure observed in as-built Inconel 625 components results in anisotropic mechanical properties. The non-equilibrium solidification in WA-DED Inconel 625 leads to severe micro-segregation of alloying elements, forming large Nb and Mo-rich Laves and carbide phases in the inter-dendritic areas. This causes a heterogeneous distribution of vital alloying elements within the γ-Ni matrix of the material, adversely affecting its mechanical properties and corrosion resistance, thereby restricting the utility of this manufacturing technique in critical applications. The incorporation of FSP has been observed to successfully eradicate the presence of typical coarse and highly oriented microstructure through grain refinement, achieving a more uniform microstructure. Through severe plastic deformation (SPD), coarse eutectic phases are broken down and redistributed within the γ-Ni matrix, enhancing the uniformity of material properties. The research thoroughly investigates the changes in microstructure, mechanical performance, and corrosion resistance of both WA-DED and FSP-enhanced WA-DED Inconel 625 samples. A Thermo-Calc simulation using the classical Scheil model was conducted to understand the solidification pathway and the formation mechanism of the Laves phase in the WA-DED sample. The grain size was significantly reduced by 98.23%, from 138 µm in the WA-DED sample to 2.44 µm in the stir zone (SZ) of the FSP-treated area, due to dynamic recrystallization (DRX), particle-stimulated nucleation (PSN), and the Zener pinning effect. This grain refinement led to remarkable enhancements in the yield strength (YS) by approximately 113%, ultimate tensile strength (UTS) by about 37% and micro-hardness by around 60% compared to the WA-DED sample. In a 3.5 wt% NaCl solution, the FSP-treated sample demonstrated superior corrosion resistance by forming a stable, thicker passive film than the as-built sample. The results of this study will offer valuable insights into utilizing the FSP technique as post-weld surface treatment of WA-DED deposited IN625 superalloy.

Nanostructuring of Ferritic Steel: A Review on Enhanced Surface Properties Using Ultrasonic Shot Peening

Nanostructuring of ferritic stainless steel refers to the process of intentionally reducing the grain size of the material at the nanoscale level. By manipulating the microstructure of the steel, it is possible to enhance its mechanical, physical, and chemical properties. Nanostructuring can significantly improve the strength, hardness, and wear resistance of ferritic stainless steel, while still maintaining its corrosion resistance. The increased density of grain boundaries and the complex dislocation network within the nanostructured material contribute to these improved properties. Moreover, the nanostructured ferritic stainless steel exhibits enhanced thermal stability, leading to better high-temperature performance and resistance to creep deformation. The small grain size also allows for increased precipitation of secondary phases, such as carbides, nitrides, or intermetallic compounds, which can further improve the material's properties. There are several methods to achieve nanostructuring in ferritic stainless steel, such as severe plastic deformation (SPD) techniques like high-pressure torsion, equal channel angular pressing, and accumulative roll bonding. These techniques impose extreme plastic deformation on the material. Leading to grain refinement below the micrometre range. Also, a novel method of surface nanostructuring ultrasonic shot peening (USP) is discussed in detail. Shot peening is a process in which small, spherical media, typically made of steel or ceramic, called "shots," are propelled onto the surface of a material at high velocities. Ultrasonic shot peening enhances the traditional shot peening process by introducing high-frequency vibrations to the shots. These vibrations are generated by an ultrasonic transducer, which is immersed in a bath of shots and liquid. The vibrations are transmitted through the liquid to the shots, causing them to collide with the surface of the ferritic steel at even higher velocities and energy levels than in traditional shot peening. In summary, nanostructuring of ferritic stainless steel offers great potential for tailoring the material's properties to meet specific application requirements, including improved strength, hardness, wear resistance, corrosion resistance, and high-temperature performance. USP is an effective surface treatment method for ferritic steel, offering advantages in terms of fatigue life, stress corrosion cracking resistance, surface hardness, and wear resistance.

Chromium/nickel-free conversion coating as cold post-treatment to anodized AA2024-T3 for corrosion resistance increase

The AA2024-T3 alloy exhibits significant properties for industrial applications, including low weight and high mechanical strength. However, its susceptibility to corrosion, attributed to precipitation hardening, requires effective surface treatments. Anodized aluminum alloys offer a robust protective structure; nevertheless, their porous layer must enable the anchoring of an additional coating or be adequately sealed. Boiling water sealing, though a non-toxic process, demands substantial energy consumption, while toxicity concerns limit the use of sealing with dichromate and Ni salts. Consequently, there is a pressing need to explore novel sealing methods capable of operating at lower temperatures for brief durations without Cr(VI) or Ni. This study proposes an alternative post-treatment for AA2024-T3 anodic layers generated in tartaric sulfuric acid (TSA). The method involves immersing the samples for 5 min in solutions containing H2ZrF6 alone, Na2MoO4 with KMnO4, and a combination of all three. The resulting layers underwent analysis using scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), open circuit potential (OCP) measurements during coating deposition, electrochemical impedance spectroscopy (EIS), and a visual examination post-immersion in a NaCl solution. The findings indicate that the Zr and Zr-Mo-Mn conversion coatings partially sealed the porous structure of the anodic oxide film, thereby enhancing its corrosion resistance in chloride medium. The incorporation of molybdate and permanganate ions intensified the precipitation of Zr oxide-fluorides within and on the porous layer, leading to improved corrosion resistance of the anodized alloy compared to Zr-only coating.

Acid Treatments of Ti-Based Metallic Glasses for Improving Corrosion Resistance in Implant Applications

Ti-based bulk metallic glasses are promising materials for metallic bone implants, mainly due to their mechanical biofunctionality. A major drawback is their limited corrosion resistance, with high sensitivity to pitting. Thus, effective surface treatments for these alloys must be developed. This work investigates the electrochemical treatment feasibility of nitric acid (HNO3) solution for two bulk glass-forming alloys. The surface states obtained at different anodic potentials are characterized with electron microscopy and Auger electron spectroscopy. The corrosion behavior of the treated glassy alloys is analyzed via comparison to non-treated states in phosphate-buffered saline solution (PBS) at 37 °C. For the glassy Ti47Zr7.5Cu38Fe2.5Sn2Si1Ag2 alloy, the pre-treatment causes pseudo-dealloying, with a transformation from naturally passivated surfaces to Ti- and Zr-oxide nanoporous layers and Cu-species removal from the near-surface regions. This results in effective suppression of chloride-induced pitting in PBS. The glassy Ti40Zr10Cu34Pd14Sn2 alloy shows lower free corrosion activity in HNO3 and PBS due to Pd stabilizing its strong passivity. However, this alloy undergoes pitting under anodic conditions. Surface pre-treatment results in Cu depletion but causes enrichment of Pd species and non-homogeneous surface oxidation. Therefore, for this glassy alloy, pitting cannot be completely inhibited in PBS. Concluding, anodic treatments in HNO3 are more suitable for Pd-free glassy Ti-based alloys.

Effect of laser shock peening on the retention ability of surface roughness in forged Cr5 steel

The roughness retention ability of the work roll surface during the cold rolling process is of great significance, especially in the production of the high-quality rolling section. Laser shock peening (LSP) is an advanced and effective surface treatment technique to improve the fatigue life, wear resistance, and other mechanical characteristics of metal components. Current studies commonly examined the reinforcement effect of single and multiple LSP treatments on Cr5 steel samples through XRD analysis, hardness testing, and residual stress measurements of different parameters. In addition, the abrasion test is widely conducted to determine the wear resistance. Compared to unprocessed samples, LSP could promote grain refinement and thus significantly increase the hardness and residual stress. Furthermore, the slight decrease in surface roughness shows that LSP treatment is an effective approach to slowing down the roughness decline rate and prolonging the roller service life. It is also found that multiple LSP impacts could remarkably improve the surface roughness retention of Cr5 steel, in which the optimal laser power density was around 23 GW/cm2.

A Comparative Evaluation of the Tensile Bond Strength of Cement-retained Restorations on Implant Abutments Subjected to Different Surface Treatments: An In vitro Study

Abstract Introduction: The longevity of cement-retained implant-supported restorations depends upon a strong and durable bond at the metal/cement interface. Various forms of surface treatments of implant abutments have been shown to enhance the retention of cement-retained restorations. The present study was undertaken to comparatively evaluate the tensile bond strength of metal copings luted onto implant abutments subjected to different surface treatments and determine the most effective surface treatment for long-term retention. Materials and Methods: Forty acrylic blocks were prepared, each with an implant analogue placed vertically inside the block and straight abutments tightened optimally onto implant analogues. The samples were divided into four Groups (n = 10) according to surface treatment of implant abutments: Group A – no surface treatment, Group B – sandblasting, Group C – metal primer application and Group D – acid etching. Metal copings were luted onto implant abutments, and the tensile force necessary to debond each metal coping was measured using a universal testing machine. Data were summarised in Mean ± Standard deviation. Groups were compared by one factor analysis of variance (ANOVA) and significance of mean difference between the groups was done by Tukey’s honestly significant difference post hoc test after ascertaining normality by Shapiro-Wilk’s test and homogeneity of variance between groups by Levene’s test. A two-tailed (α = 2) P < 0.05 was considered statistically significant. Results: The highest mean tensile bond strength was recorded for Group C (metal primer application), followed by Groups B, D and A, respectively. Conclusion: Amongst the surface treatments used in the study, metal primer application was found to be most effective in improving the retention of cement-retained prostheses.

Efficiency and Mechanism of Surface Reinforcement for Recycled Coarse Aggregates via Magnesium Phosphate Cement.

Recycled aggregate concrete (RAC) exhibits inferior mechanical and durability properties owing to the deterioration of the recycled coarse aggregate (RCA) surface quality. To improve the surface properties of RCA, the reinforcement efficiency of RAC, and the maneuverability of the surface treatment method, this study used magnesium phosphate cement (MPC), a clinker-free low-carbon cement with excellent bonding properties, to precoat RCA under three-day pre-conditioning. Moreover, variable amounts of fly ash (FA) or granulated blast furnace slag (GBFS) were utilized to partly substitute MPC to enhance the compressive strength and chloride ion penetration resistance. Subsequently, FA-MPC and GBFS-MPC hybrid slurries with the best comprehensive performance were selected to coat the RCA for optimal reinforcement. The crushing value and water absorption of RCA, as well as the mechanical strengths and durability of RAC, were investigated, and microstructures around interfaces were studied via BSE-EDS and microhardness analysis to reveal the strengthening mechanism. The results indicated that the comprehensive property of strengthening paste was enhanced significantly through substituting MPC with 10% FA or GBFS. Surface coating resulted in a maximum reduction of 8.15% in the crushing value, while the water absorption barely changed. In addition, modified RAC outperformed untreated RAC regarding compressive strength, splitting tensile strength, and chloride ion penetration resistance with maximum optimization efficiencies of 31.58%, 49.75%, and 43.11%, respectively. It was also evidenced that the improved MPC paste properties enhanced the performance of modified RAC. Microanalysis revealed that MPC pastes exhibited an excellent bond with RCA or new mortar, and the newly formed interfacial transition zone between MPC and the fresh mortar exhibited a dense microstructure and outstanding micro-mechanical properties supported with an increase in the average microhardness value of 30.2-33.4%. Therefore, MPC pastes incorporating an appropriate mineral admixture have enormous potential to be utilized as effective RCA surface treatment materials and improve the operability of RCA application in practice.

The preparation and corrosion resistance of superhydrophobic coating on Cu plate via two-step electrodeposition

PurposeThe purpose of this paper was prepared a Ni-based superhydrophobic coating on the surface of copper to enhence its corrosion resistance. The superhydrophobic coating (SHPC) has proven to be an effective surface treatment in corrosion protection. In this paper, a Ni-based SHPC was prepared on the surface of copper (Cu) to enhance its corrosion resistance.Design/methodology/approachThe coating was prepared through a two-step electrodeposition process. The first step involves the formation of a micro-nano structure Ni layer formed by an electrodeposition process. Subsequently, the polysiloxane layer was deposited on the Ni surface to create an SHPC. The morphology, composition, structure, wettability and corrosion resistance of the coating were characterized and discussed.FindingsThe results show that the water contact angle of the as-prepared coating reaches 155.5°±1.0°. The corrosion current density (icorr = 3.90 × 10−9 A·cm−2) decreased by three orders of magnitude compared to the substrate, whereas |Z|f = 0.01 Hz (2.40 × 106 Ω·cm2) increased by three orders of magnitude. It indicated that the prepared coating has excellent superhydrophobicity and high corrosion resistance, which can provide better protection for the substrate.Originality/valueThe prepared coating provides long-lasting protection for Cu and other metals and offers valuable data for developing SHPCs.

Study of Wear of an Alloyed Layer with Chromium Carbide Particles after Plasma Melting

Depending on operating conditions, metals and alloys are exposed to various factors: wear, friction, corrosion, and others. Plasma surface alloying of machine and tool parts is now an effective surface treatment process of commercial and strategic importance. The plasma surface alloying process involves adding the required elements (carbon, chromium, titanium, silicon, nickel, etc.) to the surface layer of the metal during the melting process. A thin layer of the compound is pre-applied to the substrate, then melted and intensively mixed under the influence of a plasma arc, and during the solidification process, a new surface layer with optimal mechanical properties is formed. Copper-based alloys—Cu-X, where X is Fe, Cr, V, Nb, Mo, Ta, and W—belong to an immiscible binary system with high mechanical strength, electrical conductivity, and magnetism (for Fe-Cu) and also high thermal characteristics. At the same time, copper-based alloys have low hardness. In this article, wear tests were carried out on coatings obtained by plasma alloying of CuSn10 and CrxCy under various friction conditions. The following were chosen as a modifying element: chromium carbide to increase hardness and iron to increase surface tension. It is noted that an increase in the chromium carbide content to 20% leads to the formation of a martensitic structure. As a result, the microhardness of the layer increased to 700 HV. The addition of CuSn10 + 20% CrxCy and an additional 5% iron to the composition of the coating improves the formation of the surface layer. Friction tests on fixed abrasive particles were carried out at various loads of 5, 10, and 50 N. According to the test results, the alloy layer of the Fe-Cr-C-Cu-Sn system has the greatest wear resistance under abrasive conditions and dry sliding friction conditions.

Rapid Surface Reconstruction in Air-Processed Perovskite Solar Cells by Blade Coating.

Blade coating has been developed to be an essential technique for large-area fabrication of perovskite solar cells (PSCs). However, effective surface treatment of the perovskite layer, which is a critical step for improving PSC performance, remains challenges during blade coating due to the short interaction time between the modification solution and the perovskite layer, as well as the limited selection of available organic solvents. In this study, a novel modifier N,N-diphenylguanidine monohydrobromide (DPGABr) dissolved in acetonitrile (ACN) is blade coated on the MA0.7 FA0.3 PbI3 surface in air to reconstruct the perovskite surface in hundreds of milliseconds. This work finds that the solvent ACN rapidly dissolves organic iodide of the perovskite layer and leads to a PbI2 -rich surface, providing reactive sites for DPGABr to form a thin DPGABr/PbI2 complex layer. This surface reconstruction can effectively passivate defects and induce n-type doping on the perovskite surface to facilitate electron transfer. The resultant devices show a 15% improvement in average power conversion efficiency. More importantly, the devices with the surface reconstruction show outstanding long-term stability, with negligible performance degradation even after 1-year storage in air. This study presents a convenient and effective approach for improving the performance of blade-coated PSCs prepared in air.

Preparation of wear‐resistant ceramic coating by dynamically controlling the resistance during MAO

AbstractMicro arc oxidation (MAO) is a surface treatment technology that typically involves immersing the valve metal in an electrolyte to generate a ceramic coating for improved surface characteristics. This paper proposes a novel MAO g48 the need for electrolyte immersion. The MAO power supply's positive electrode is connected to the valve metal as the anode, while the negative electrode is connected to a stainless‐steel wire in the electrolyte circulation system. The distance between the cathode and anode is dynamically adjusted using a mechanical arm. Through advanced techniques like X‐ray diffraction and X‐ray photoelectron spectroscopy, successful ceramic coatings comprising α‐Al2O3 and γ‐Al2O3 phases on aluminum substrates were achieved. Tribological experiments demonstrated that coatings prepared with a cathode‐anode distance of 1.0 cm exhibited a scratch width of approximately 286.160 μm, while a distance of 3.0 cm resulted in approximately 1736.80 μm. This highlights the significant impact of the cathode‐anode distance on the wear resistance of the plasma electrolytic oxidation ceramic coating, with optimal performance observed at 1.0 cm. Utilizing a robotic arm to control the cathode movement enables effective surface treatment of large workpieces and targeted regions, addressing practical challenges in MAO applications.

In-situ constructed protective bilayer enabling stable cycling of LiCoO2 cathode at high-voltage

The practical application of high-voltage lithium cobalt oxide (LCO) has been hampered by the severe degradation of its structural integrity. In this work, a protective bilayer was fabricated on LCO surfaces by means of large-scale and facile electrolyte engineering. The protective bilayer consisting of a LiF-rich cathode-electrolyte interphase (CEI) as the outermost layer and a layer of disordered spinel structure as the inner layer was uniformly fabricated in-situ. The high-resistance CEI layer inhibited the fast transfer of Li ions from LCO to bulk electrolyte during the first few cycles, resulting in the significantly increased local overpotential on the LCO surface. As a consequence, the LCO surface underwent a phase transformation from the layered phase to the spinel phase first, forming the spinel phase inner layer due to the voltage rising beyond 4.55 V (vs. Li/Li+). The CEI and spinel layers effectively blocked the dissolution of transition-metal (TM) ions into the electrolyte during cycling and inhibited the formation of the structurally defective rock-salt phase that would hasten cycling-induced structural degradation. The formation of the protective bilayer effectively prevented the phase transition from the bulk layered LCO structure into spinel and then rock salt, thereby reducing decay of its cycling capacity. Remarkably, the graphite||LCO pouch cell with optimized electrolyte retained 78.9% of its capacity even after 1000 cycles under the operation voltage window of 3.0–4.55 V (vs. Li/Li+). This study provides guidance for the development of effective surface treatment strategies for stable layered cathodes with high capacity and cyclability.

Dry wear behavior of identical tetrahedral amorphous carbon nanofilms on sintered composites and metal substrate with varying load bearing capacities

Diamond-Like Carbon (DLC) coating is an effective surface treatment method for improving the tribological properties of machine elements and tool materials. Among them, the tetrahedral amorphous carbon (ta-C) coating has recently received much attention due to its high hardness and good heat resistance. When characterizing friction and wear patterns related to the lifetime and cost, the thickness of the ta-C coating and the type of substrates play an important role. In this paper, ta-C coatings of two thicknesses are deposited on 304 stainless steel (SS) and cemented carbide (WC–Co), which have significant differences in mechanical properties, through filtered cathodic vacuum arc (FCVA) equipment. After ta-C coating on substrates, the tribological properties of each sample are investigated. As a result, compared to bare materials, ta-C-coated materials have a reduced coefficient of friction and improved wear resistance. However, as the base material is softer, tearing occurs in a thin coating so that a thicker ta-C coating might improves the tribological properties. Since thicker ta-C coatings do not always improve tribological properties, the efficiency can be increased by customizing the ta-C coating thickness according to the substrate layer material.

Improved wear and corrosion resistance of biomedical TiZrNbTaMo medium-entropy alloy by thermal oxidation treatment

Thermal oxidation treatment was carried out on novel TiZrNbTaMo biomedical Medium-entropy alloy (bio-MEAs) at 400∼600 °C for 2 h in air. The extracted results demonstrated that the oxide layer was mainly composed of oxides of Zr and Ti, in which the content of ZrO2 and TiO2 with high hardness increased with the increase of oxidation temperature, leading to enhanced wear resistance (wear rate reduced from ∼10−4 to ∼10−5 mm3/N⋅m). Likewise, the oxide layer also improves the corrosion resistance of the alloys. The results showed that thermal oxidation can be used as an effective surface treatment method to broaden the application prospects of bio-MEAs.

A super wear-resistant coating for Mg alloys achieved by plasma electrolytic oxidation and discontinuous deposition

Magnesium alloys are lightweight materials with great potential, and plasma electrolytic oxidation (PEO) is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys. However, the ∼14 µm thick and rough PEO protection layer has inferior wear resistance, which limits magnesium alloys as sliding or reciprocating parts, where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting. Here a novel super wear-resistant coating for magnesium alloys was achieved, via the discontinuous sealing (DCS) of a 1.3 µm thick polytetrafluoroethylene (PTFE) polymer layer with an initial area fraction (Af) of 70% on the necessary PEO protection layer by selective spraying, and the wear resistance was exceptionally enhanced by ∼5500 times in comparison with the base PEO coating. The initial surface roughness (Sa) under PEO+DCS (1.54 µm) was imperfectly 59% higher than that under PEO and conventional continuous sealing (CS). Interestingly, DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS. DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks, and DCS also provided extra space for the movement of nano-blocks, which resulted in rolling friction and nano lubrication. Further, DCS promoted mixed wear of the PTFE polymer layer and the PEO coating, and the PTFE layer (HV: 6 Kg·mm−2, Af: 92.2%) and the PEO coating (HV: 310 Kg·mm−2, Af: 7.8%) served as the soft matrix and the hard point, respectively. Moreover, the dynamic decrease of Sa by 29% during wear also contributed to the super wear resistance. The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.

Effect of roller burnishing on the mechanical behavior and surface quality of Ti6Al4V alloy

A low-cost and effective surface treatment technique that has gained popularity recently is roller burnishing. In this procedure, the rolling element is forced against the surface with a specified amount of force, which results in small plastic deformations that reduce surface roughness without removing chips from the surfaces. The method results in a considerable decrease in surface roughness while the material's surface hardness rises. The effects of roller burnishing process parameters (burnishing pressure, number of passes, and feed rate) on Ti6Al4V tensile strength and surface roughness were investigated experimentally in this study. In the study, the burnishing procedure was carried out via a specifically created disc-shaped equipment using the Taguchi L16 experimental design approach. The study's findings showed that the roller burnishing technique improved the Ti6Al4V alloy's surface quality, microhardness and ultimate tensile strength. It was shown that roller burnishing increased the surface roughness, microhardness and ultimate tensile strength by 64%, 16,25%, and 94%, respectively.