Austenitic Stainless Steel Substrate Research Articles

Comparative investigation on the microstructure and corrosion properties of surfacing cobalt alloys by various methods

This study applies three welding methods, namely tungsten inert gas (TIG) welding, laser welding, and plasma arc welding methods, to perform cobalt alloy surfacing on austenitic stainless steel substrates, and compares their microstructure and corrosion properties. The results reveal that samples obtained through all three methods exhibit excellent metallurgical bonding between the austenitic stainless steel substrate and the cobalt alloy surfacing layer, with no defects such as cracks, pores, or inclusions being observed. Among them, the cobalt alloy surfacing layer produced by laser welding shows a finer and more uniform microstructure, displaying a distinct growth direction along the surfacing direction away from the interface. Additionally, electrochemical polarization curve testing demonstrates that the corrosion resistance of the laser-welded surfacing layer surpasses that of TIG welding and plasma arc welding, exhibiting a lower corrosion rate. Consequently, this study offers valuable insights into the selection of cobalt alloy surfacing welding methods on austenitic stainless steel substrates and the evaluation of the corrosion properties for the cobalt alloy surfacing layer, providing essential guidance for engineering practices in the power plant valves.

Preparation of Ordered Nanohole Arrays by Two-Step Anodization of Austenitic Stainless Steel Substrates.

An anodic oxide film with a regular pore arrangement was formed by the two-step anodization of an austenitic stainless steel (JIS SUS304) substrate. In this study, we determined the anodization conditions under which the pore arrangement in the anodic oxide film became self-organized. After removing the anodic oxide film formed by the first anodization with a mixture containing CrO3 and HF, the residual substrate was anodized under the same conditions as those in the first anodization. As a result, we found that it was possible to form an anodic oxide film with pores arranged in a regular pattern from the surface to the bottom. This is the first report on the formation of anodic oxide films with ordered nanohole array structures by the two-step anodization of austenitic stainless steel. The interpore distance of the resulting nanohole array structures can be controlled by changing the anodization conditions. By measuring the capacitance of the anodic oxide film, we confirmed that its properties depended on the heat-treatment temperature and pore depth. In addition, no significant decrease in the capacity of anodic oxide films with ordered nanohole array structures was observed, even when the scan rate of the cyclic voltammogram measurement was increased. This is considered to be because the cylindrical pores facilitate ion diffusion to the bottom of the holes. Anodic oxide films obtained by the anodization of austenitic stainless steel substrates can be applied as electrodes for capacitors.

Quantification of δ-ferrite and austenite retention in laser-deposited martensitic stainless steel

Type 420 martensitic stainless-steel powder was clad onto a CF3M austenitic stainless steel substrate using laser direct-energy-deposition (L-DED). Through comprehensive characterization and numerical simulation, the evolution of microstructures, particularly the retention of δ-ferrite and austenite, was investigated. In the clad fusion zone, the primary phase to solidify was δ-ferrite, followed by austenite resulting from the peritectic reaction. The segregation patterns developed during rapid solidification from the L-DED process exerted a significant effect on the stability of the austenite in the room temperature microstructures. Due to the fast cooling rate in the solid state, the time available for transformation of the δ-ferrite to austenite regarding the segregation patterns was limited, and the transformation was incomplete. The room temperature microstructure was therefore comprised of δ-ferrite distributed in the dendrite core regions, surrounded by martensite, which was further surrounded by a small fraction of retained austenite in the interdendritic regions. The retained austenite region was enriched with segregated alloying elements, which pushed the martensite start temperature Ms below room temperature. The retention of both δ-ferrite and interdendritic austenite was proved to have caused a softened fusion zone with a lowered martensite fraction.

Optimization of Antibacterial properties of 316 Austenitic Stainless Steel

In the present study, titanium dioxide (TiO2/Chitosan) nano-particles layer coatings were fabricated by electrophoretic deposition on 316 Austenitic Stainless steel substrate. Aims to enhance antibacterial properties by coating the surface with a bio ceramic (TiO2) nano-powders. TiO2, were made on 316 austenitic stainless steel substrate with an EPD (electrophoretic deposition) technique, charged particles suspended in ethanol at a concentration of 50 g/L, for each powder with ideal conditions of 20V and a deposition time of (2, 4 and 6 min). The surface tests of coated substrates, such as, micro-hardness, surface roughness and wettability antibacterial test were evaluated and compared to that of the uncoated substrates. The showed results the electrophoretic deposition is a favorable technique to make a bio coating on 316 Austenitic Stainless steel substrate with excellent properties and structure for applications biomedical. The results demonstrated that the coated sample under coating conditions (20V, 2min) which is close to the ratio found in living bone. the average micro-hardness of the TiO2 coated sample is 1483 HV compared with that of uncoated substrates is 460 HV. The results also of the wettability test showed that the contact angle of the deposited paint is 5.9 degrees, and this positive result is useful for biomedical applications and proved that the coating is hydrophilic.

Combining Carbon Nanoparticle Coatings and Laser Surface Texturing for Enhanced Lubricity Under High Loads

Developing new lubrication concepts greatly contributes to improving the energy efficiency of mechanical systems. Nanoparticles such as those based on carbon allotropes or 2D materials have received widespread attention due to their outstanding mechanical and tribological performance. However, these systems are limited by a short wear life. Combining nanoparticle coatings with laser surface texturing has been demonstrated to substantially improve their durability due to the reservoir effect which prevents immediate particle removal from the contact. In this study, we investigate the high-load (20 N) tribological performance of AISI 304 austenitic stainless-steel substrates, which are line-patterned by laser interference patterning and subsequently coated with different carbon nanoparticle coatings (carbon nanotubes, carbon onions, carbon nanohorns) against alumina and 100Cr6 counter bodies. In addition to that, benchmark testing is performed with conventional solid lubricant coatings (graphite, MoS2, WS2). Electrophoretic deposition is used as the main coating technique along with air spraying (for WS2). All coatings substantially improve friction compared to the purely laser-patterned reference. Among all coating materials, carbon nanotubes demonstrate superior lubricity and the longest wear life against 100Cr6 and alumina counter bodies. Detailed characterization of the resulting wear tracks by energy-dispersive X-ray spectroscopy, scanning electron microscopy, and confocal laser scanning microscopy provides insights into the friction mechanisms of the various solid lubricant particles. Further, material transfer is identified as an important aspect for effective and long-lasting lubrication.

A controllable fabrication strategy of anodic oxides film with dense, nano-porous and open-top ordered porous arrays morphology on 304 stainless steel in fluoride-based ethylene glycol electrolyte

A facile anodizing strategy without using perchloric acid was reported in this work to controllably produce three different types of self-organized structure anodic oxides films with dense, nano-porous and open-top ordered porous arrays structure morphology. These oxides were developed on 304 austenitic stainless steel (SS) substrate in fluoride-based ethylene glycol electrolyte by simply regulating the H2O concentration in the electrolyte and anodizing voltages. From our analysis, it was found that the above-mentioned anodizing parameters significantly affect the morphologies of the anodic oxides film rather than the chemical composition. The chemical compositions of the different types of films were α-Fe2O3 and Cr2O3 or (FexCr1-x)2O3 composite oxides. Moreover, the higher (70 V), middle (50 V), and lower voltages (30 V) were respectively suitable for the preparation of the dense, nano-porous, and open-top ordered porous arrays morphology structure anodic oxides film due to the different anodized film formation rate, respectively. Finally, a plausible formation-dissolution mechanism was provided by considering the dissolution effect with the assistance of the oxygen evolution derived from H2O, which is favourable to form the sparser anodized film on the SS substrate. In addition, the anodizing parameters selected principle for the corresponding anodic oxides layers with different morphologies onto the SS substrate. The controllable fabrication strategy of the various film will greatly broaden the application of the SS substrate in both anti-corrosion and decoration fields.

Effect of Defocusing Distance on Microstructural, Hardness, and Tribological Behavior of Ni-Cr-Si-B-C Powder Deposit on 316LN Austenitic Stainless Steel Substrate Using Laser Hard-Facing

The Ni-based alloy powder has been melted and bonded to an AISI 316LN austenitic stainless steel (ASS) base material (substrate) using a high-energy disc laser with a maximum power of up to 12 kW. The substrate’s hard-faced reservoir is highly diluted due to the significant difference in melting temperature between the substrate and the commonly used Ni-based alloy. The hardness, macrostructure, microstructure, and wear resistance effects of the defocusing distance were examined. The composition, microstructure, hardness, and wear resistance of phases have been examined with a pin-on-disk wear test, an energy dispersion spectroscopy (EDS), a scanning electron microscope (SEM), and X-ray diffraction (XRD). According to the findings, the height and diameter of the beads rose when the distance was increased from 17 mm to 37 mm. On the other hand, penetration and dilution decreased from 3.7 mm to 2.7 mm and from 9.7% to 3.1%, respectively. When the defocusing length is increased and the penetration profundity and dilution are limited, the density of energy per unit clad is accessible. The laser hard-faced surfaces contain microstructures of Ni-rich solid solution, boride, and carbide. These different factors cause higher hardness and resistance to wear.

Preparation and Performance Study of Si-DLC Based on Ion Deposition of Different Multiple Gradient Transition Layers

In order to improve the lower adhesion strength of Si-DLC coatings to the substrate and enhance its wear resistance, Si-DLC coatings with different transition layers (AlTiSiN, AlCrN and AlTiCrN) were prepared on 304 austenitic stainless steel substrates using multi-arc ion plating technique. The effects of different transition layers on the properties of Si-DLC were characterized by scanning electron microscopy, X-ray diffractometer, nanoindentation, confocal microscopy, Rockwell hardness tester, Raman test and wear test to find the optimal Si-DLC transition layer. The results show that the Si-DLC coating with AlTiSiN as the transition layer has an ID/IG of 0.71, the highest hardness of 26.7 Gpa, low surface roughness, the highest compressive stress, the best bond strength and the best wear resistance.

Structure and fracture toughness of TiAlN thin films deposited by deep oscillation magnetron sputtering

TiAlN thin films were deposited on Si(100) and AISI 304 austenitic stainless steel substrates at the low deposition temperature below 250℃ by the deep oscillation magnetron sputtering (DOMS), respectively. The peak sputtering power changed from 58.7 kW to 129.9 kW by adjusting the oscillation voltage on-time (τon) / off-time (τoff) ratio with 6–12 μs to 30 μs. All TiAlN thin films have a face centered cubic structure with a composition of Ti0.22Al0.28N0.50. With increasing the peak powers, a transit of the columnar morphology in Zone I with the preferred orientation of c-TiAlN(111) to a compact morphology in Zone T with c-TiAlN(200) was characterized. The hardness, residual stress, and H/E and H3/E2 ratios of TiAlN thin films increased with the maximal values obtained at the peak power of 90.2 kW, and then slightly decreased. Correspondently, the fracture toughness (KIC) of TiAlN thin films on Si(100) and AISI 304 stainless steel increased firstly from 0.56 MPa∙m1/2 to 1.10 MPa∙m1/2 and from 0.58 MPa∙m1/2 to 1.08 MPa∙m1/2 as the structure from Zone I with c-TiAlN(111) to Zone T with c-TiAlN(200), and then decreased to 0.94 MPa∙m1/2 and 0.71 MPa∙m1/2 at the structure of Zone T with c-TiAlN(200), respectively. The higher KIC values of Ti0.22Al0.28N0.50 thin films in Zone T were achieved on Si(100) and AISI 304 stainless steel at 90.2 kW. The excellent mechanical properties of TiAlN thin films on Si(100) and AISI 304 stainless steel substrates were carried out by using DOMS at the low deposition temperature.

Investigation into the formation of Ni splats plasma-sprayed on to mild steel and stainless steel substrates

The present study investigates the splat formation behaviour of Ni particles plasma sprayed onto AISI 1008 mild steel and 316 austenitic stainless steel substrates to draw a comparative analysis of splat formation on both surfaces. A range of analytical techniques were used to analyse the surface and cross-sectional characteristics of the splats formed on both substrates. Most of the splats observed on both of the substrates were halo type splats driven by Rayleigh–Taylor instabilities. A linear relationship was identified between the size of the central core of the splats and their outer ring of debris, which was distinct for each substrate. The diffusion profile, obtained through STEM-EDS analysis, revealed a higher degree of diffusion across the interface between splat and stainless steel substrate as compared to mild steel, suggesting a better bond efficiency for stainless steel. Cross-sectional observations, together with theoretical calculations, showed evidence of substrate melting as well as the presence of metallurgical bonds for both mild steel and stainless steel substrates.

Synthesis of multifunctional microdiamonds on stainless steel substrates by chemical vapor deposition

We report on the synthesis of multifunctional microdiamonds by chemical vapor deposition (CVD) on 304 and 316 austenitic stainless steel (SS) substrates. The increase in wettability achieved by surface scratching and the structure of ultra-dense Q-carbon achieved high nucleation density and minimized strains in diamond films. Notably, these diamond films exhibit a high amount of twinning, leading to the formation of five-fold microdiamonds. The diamonds on scratched SS substrate and Q-carbon interlayer exhibit a full width at half maximum of 8.25 cm−1 and 11.5 cm−1, compared to 26 cm−1 on bare SS substrate. The diamond films grown on bare SS substrate exhibited cracking due to high tensile stress of 2.3 GPa, ascribed to thermal mismatch between SS and diamond. The electron backscattered diffraction investigations reveal iron inclusions in diamonds synthesized on bare SS substrates, which may create ferromagnetism in these diamonds. This route, compared to the ion beam implantation method using ferromagnetic ions, yields better samples. At 800 °C, 1012 Fe atoms/cm2s are transferred from the SS substrate into the diamonds. The dominant growth orientation for these CVD diamonds was determined to be <110> out of plane. These multifunctional microdiamonds are useful for biomedical, electronic, and tribological applications.

Investigation of Microwave Processing Parameters on Development of Ni-40Cr3C2 Composite Clad and Their Characterization

The chromium carbide (Cr3C2)-reinforced Ni-based composite clad on austenitic stainless steel (SS-316) substrate was successfully developed by the microwave cladding route after optimizing process parameters (Power: 900 Watt, Exposure Time: 380 seconds). Clads were developed at 2.45 GHz frequency in a domestic microwave oven. The developed composite clad has been examined for metallurgical and mechanical properties. The investigation was carried out by using scanning electron microscopy (SEM) equipped with a backscatter electron detector, energy dispersive spectroscopy (EDS) for elemental analysis, and X-ray diffractometry (XRD) for phase analysis and their quantification and Vicker’s microhardness tester for microhardness. Clads of thickness 600 µm were successfully developed, which are free from visible pores and all types of cracks (interfacial or solidification cracks). The porosity analysis was carried out by using ASTM B-276 standard, and results reveal that porosity is less than 2 pct. The average microhardness of the developed clad is observed 605 ± 80 HV0.3. The developed clad was three times harder than the substrate (SS-316). The various intermetallic (Ni3Fe, Cr3Si, and Ni2Si) and different carbides (Cr7C3, NiC, Ni3C, SiC, and Cr3Ni2SiC) phases were observed through XRD examination. The distribution of intermetallic and various hard carbide phases in the clad has a direct influence on hardness and increases hardness at great extent.

Fabrication of ultrahard Q-carbon nanocoatings on AISI 304 and 316 stainless steels and subsequent formation of high-quality diamond films

Ideal coatings require three critical elements: hardness, toughness, and adhesion. Coatings of diamond-related materials are appealing owing to their high hardness but exhibit inadequate adhesion and toughness, especially on stainless steel substrates. Q-carbon, a newly discovered allotrope of carbon has the potential to improve hardness, toughness, and adhesion. The Q-carbon is formed on melting and quenching from super undercooled melt state. In this study, we have synthesized robust Q-carbon/α-carbon and Q-carbon/nanodiamond heterostructures on austenitic stainless steel substrates by laser annealing amorphous carbon films with nanosecond laser pulses above melt threshold (ED). Maximum melt regrowth velocity of 13 m/s corresponding to Q-carbon/nanodiamond composite was obtained by laser-solid melt interaction simulations. Subsequently, Q-carbon was used as seed layer to grow microdiamonds by HFCVD (hot filament chemical vapor deposition). The Q-carbon seed layer helped growth of better quality diamonds (50% less graphitic) with FWHM of 11.5 cm-1 and demonstrated higher nucleation density in comparision with amorphous carbon-coated and bare 316 SS substrates. Diamonds grown on Q-carbon displayed ballas type of microstructure indicative of high toughness. This study on Q-carbon nanocomposite coatings provides a new pathway for fabricating ultrahard carbon-based coatings on stainless steels for biomedical and tribocorrosive applications.

Stress corrosion cracking of simulated heat-affected zone in a CF8A weld in high temperature water

In this study, thermal simulation was performed to conduct thermal cycles on CF8A cast austenitic stainless steel substrates with different ferrite contents to simulate the microstructures that form near a weld fusion boundary. The effects of ferrite content and morphology on the mechanical properties of CF8A were investigated. The stress corrosion cracking (SCC) susceptibility of the specimens was evaluated with slow strain rate tensile (SSRT) tests in a simulated boiling water reactor (BWR) coolant environment.The results indicated that an increase in the ferrite content of the CF8A base metal led to a minor increase in hardness. Thermal simulation caused a marked increase in ferrite content, especially in the high ferrite CF8A substrate. The yield strengths of the tested samples increased obviously with increasing ferrite content, but the ductility decreased. The ultimate tensile strengths of the samples reached a plateau when the ferrite number (FN) was greater than 18. The applied thermal simulation greatly improved the impact toughness of high ferrite CF8A in comparison with the original substrate. The results indicated that the samples with high ferrite content had a shorter rupture life but greater fracture strength than those with low ferrite content strained in high temperature water. Moreover, cleavage-like fracture was found in all of the samples that suffered from SCC. The SCC cracks were observed to be more likely to propagate along the δ/γ interfaces of a CF8A. Furthermore, crack initiation and growth inside the γ of low ferrite CF8A contributed to a great loss in strength in a high temperature water environment.

AFM Measurements of the Deformation Kinetics of Silica Oxide Dots Deposited on a Sequentially Nitrided Stainless Steel

In this paper, we present the results of plasma nitriding treatments on austenitic stainless steel substrates previously coated with a patterned silicon oxide layer. For this purpose, masks were made by PECVD for the deposition of a silicon oxide layer on polished austenitic AISI 316L samples. For the final nitriding treatment, we used a multi-dipolar plasma providing independent substrate polarization. The interactions between expanded austenite and fixed silicon oxide mask in different shapes (circular and square dots) are observed by atomic force microscopy (AFM) on the same area before and after the nitriding treatment. After this thermochemical treatment, we obtain strong distortions of the dots, in particular at the edges of the larger size dots. The role of elastic deformation, due to the expanded austenitic phase formed by the diffusion of nitrogen under the mask is of primary importance.

Effects of consecutive processing between cleaning and deposition on adhesion of diamond-like carbon prepared by plasma-based ion implantation and deposition

The effects of pretreatment on adhesion, which is the most important challenge of diamond-like carbon (DLC) films, were investigated. DLC films were prepared by changing pretreatment conditions on austenitic stainless steel (SUS304) substrates by hybrid process of plasma-based ion implantation and deposition (PBIID) using superimposed RF and negative high-voltage pulses. Although an oxide layer on a substrate surface was removed by Ar-plasma sputter cleaning, the substrate surface was immediately reoxidized when plasma was stopped for a moment between sputter cleaning and deposition. The DLC film on the oxide layer was poor adhesion strength less than approximately 50 MPa. Even if the oxide layer existed on the substrate surface, carbon ion implantation as an interface treatment in the PBIID process broke the oxide layer. As a result, the adhesion strength of DLC films was enhanced above the strength of epoxy resin (about 70 MPa). Furthermore, it was found that continuous generation of plasma after sputter cleaning was able to suppress reoxidation of the substrate surface. Consequently, the adhesion strength of DLC films prepared with no interface treatment was increased above 70 MPa, suggesting simplification of coating process and reduction in processing time for cost reduction.

Hydrogen Permeation of Multi-Layered-Coatings

Using a substrate of AISI 316L austenitic stainless steel, which is used for components in high-pressure hydrogen systems, the hydrogen barrier properties of samples with single-layer coatings of TiC, TiN, and TiAlN as well as a multi-layered coating of TiAlN and TiMoN were evaluated. The ion plating method was used, and coating thicknesses of 2.0–2.6 μm were obtained. Hydrogen permeation tests were carried out under a differential hydrogen pressure of 400 kPa and at a temperature between 573 and 773 K, and the quantities of hydrogen that permeated the samples were measured. This study aimed at elucidating the relationship between the microstructures of the coatings and the hydrogen permeation properties. Coatings of TiC, TiN, TiAlN, and TiAlN/TiMoN facilitated reductions of the hydrogen permeabilities to 1/100 or less of that of the uncoated substrate. The samples coated with TiN and TiC that developed columnar crystals vertical to the substrate exhibited higher hydrogen permeabilities. The experiment confirmed that the coatings composed of fine crystal grains were highly effective as hydrogen barriers, and that this barrier property became even more efficient if multiple layers of the coatings were applied. The crystal grain boundaries of the coating and interfaces of each film in a multi-layered coating may serve as hydrogen trapping sites. We speculate that fine crystal structures with multiple crystal grain boundaries and multi-layered coating interfaces will contribute to the development of hydrogen barriers.

Corrosion Behavior of Thermally Sprayed WC-Co-VC Coatings in NaCl Aqueous Solution

WC-17Co coatings are used to protect components against wear, high temperature and corrosion. WC based cermet coatings have been considered as alternative replacements to traditional hard chrome plating for improve surface properties of aircraft landing gear. This coatings are used in engineering applications requiring superior hardness and improved wear resistance, little is known about the corrosion resistance. In this study, four WC-17Co based composite coatings were deposited onto austenitic stainless steel substrates using high velocity oxygen fuel (HVOF) spraying at different concentrations of VC. The corrosion behavior was performed by linear polarization resistance test, potentiodynamic polarization curves and electrochemical impedance spectroscopy in saline environment. Characterization of the coating structure, morphology and composition, was carried out, prior to and after corrosion testing, using scanning electron microscopy and EDX elemental analysis. It was determined that the anodic branches present a tendency to passivation this more pronounced in sodium chloride. The results showed the addition of nanostructured WC-17Co particles improved corrosion resistance in H2O and NaCl. The addition of VC did not affect the corrosion behavior of the bimodal thermal spray coating. The electrochemical data showed that sample with 50 % of nanoparticles of WC-17Co presented higher corrosion resistance than the others in chloride solutions.

Correlation between Travel Speed, Microstructure, Mechanical Properties and Wear Characteristics of Ni-Based Hardfaced Deposits over 316LN Austenitic Stainless Steel

Abstract Laser hardfacing were produced using a high power Disk laser of 4 kW maximum power as a heat source to melt and bond the Colmonoy-5 powder on to AISI 316 LN stainless steel substrate. Significant difference in melting points between the austenitic stainless steel (ASS) substrate and Ni-based Colmonoy alloy results in substantial dilution of the hardfaced deposit from the substrate. In this present study, the effect of travel speed (TS) on microstructure, microhardness and wear characteristics laser hardfaced deposits were investigated. The phase constitution, microstructure and hardness of laser hardfaced deposits were examined by optical microscope, scanning electron microscope, energy dispersion spectroscopy, x-ray diffraction and Vickers hardness tester. The TS was varied between 300 and 500 mm/min. The other parameters such as, laser power, powder feed rate, and defocusing distance were kept constant. From this investigation, it is found that the deposit hardness increased from 750 HV to 800 HV with decreasing in TS. The TS increases, bead height decreased and dilution and depth of penetration increased. Due to higher TS the faster cooling rate takes place, it causes the cracking and porosity. Microhardness and wear resistance are slightly improved in the TS of 400 mm/min. The microstructures of deposit layer are composed of Ni-rich carbide, boride and silicide, this are the responsible for higher hardness and better wear resistance.

Aluminum Coating Influence on Nitride Layer Performance Deposited by MO-CVD in Fluidized Bed on Austenitic Stainless Steel Substrate

The modification of surface properties by duplex treatments, involving the overlapping of two surface treatment techniques, has been established as an intelligent solution to create new applications for the substrate metallic material. There are driveline components operating under very tough wear and corrosion conditions, with high temperature and humidity variations. Such components are usually made of high Cr and Ni stainless steel and for the hardening of surfaces it is recommended a thermo chemical treatment. Since stainless steels, especially austenitic stainless steels, are difficult to nitride, experimental studies focus on increasing the depth of the nitride layer and surface hardness. Achieving the goal involves changing active layer chemical composition by introducing aluminum in the surface layer. In order to find a solution, a new surface treatment technique is produced by combining aluminum thin films by MO-CVD in a fluidized bed using a triisobutylaluminum precursor with a thermo chemical nitriding treatment.