316L Stainless Steel Substrates Research Articles

Al2O3 Coatings for Protection of Stainless Steel 316L against Corrosion in Zn-Al and Zn-Al-Mg

The production and quality of automotive-grade galvanised steel are affected by the limited service life of the pot roll bearings used in continuous galvanising lines. The journal bearings are subjected to severe degradation as they react with the molten Zn bath, and coatings can provide corrosion protection to the bearing materials. This research investigates the performance of Al2O3 coatings applied via the HVOF thermal spray process to stainless steel 316L substrates. Immersion tests were conducted in baths of different compositions, namely GI (Zn-0.3 wt.% Al) and ZMA (Zn-1.5 wt.% Al-1.5 wt.% Mg). Material characterisation after testing showed evidence of coating degradation after 1 week, as the coating tended to crack and detach from the substrate, allowing the molten Zn to attack the underlying steel. The coefficient of thermal expansion of Al2O3 and steel was measured, and a difference of 13 × 10−6 K−1 was found, leading to the development of cracks in the coatings. Zn penetration through cracks was determined to be the main failure mechanism of the Al2O3 coatings, which otherwise remained inert to Zn-Al. Conversely, the coatings immersed in Zn-Al-Mg reacted with the Mg in the molten metal bath, showing that changing bath composition affected the performance of the coatings in molten Zn alloy.

Electrochemical Investigations of Ag and Bi in Choline Chloride-Ethylene Glycol DES Electrolyte

Electrodeposition for silver and bismuth is currently carried out in alkaline solutions, e.g., by use of cyanide, and by electroplating these metals, by themselves or together. The electroplated products have important uses, e.g., in semiconductors [1].Choline Chloride (ChCl)-Ethylene Glycol (EG) DES mixtures, often referred to as ethaline, have been shown to have superior electrochemical properties compared to many other DES systems [2]. This system is considered a green solvent [3]. In this work, the electrochemical behaviour of Ag and Bi in ethaline electrolyte has been investigated to obtain the necessary parameters to extract them by electrochemical methods, either separately or together, when both are present in the DES electrolyte. The presence of Cu and Sb in the electrolyte, has also been studied, and its effect in the metal obtained has been evaluated. Ethaline solutions were fabricated by mixing together ChCl and EG at 1:2 ChCl:EG molar ratio by stirring at 60 °C until a clear liquid was formed. Model electrolyte solutions were then produced by dissolving AgCl and BiCl3, as well as SbCl3 and CuCl2, in the DES. Electrochemical investigations were carried out at 60 °C by cyclic voltammetry (CV), chronoamperometry (CA) and potentiostatic electrolysis using a 3-electrode setup.The CVs obtained using Pt-wire or GC-rod as working electrodes in the DES with 10 mM Ag(I) and Bi(III), showed two distinguished peaks in the cathodic scan. The CV and CA results showed that the Bi deposition starts at approximately 0.15-0.20 V more cathodic than the Ag deposition. Two or more electrochemical signals were observed in the reverse anodic scan, correlating to the dissolution of the metals, alloys and possible electrolyte reactions. Example of CV curve obtained on a Pt wire at a scan rate of 200 mV/s is included.The results indicated that it could be possible to electrochemically extract only Ag or both Ag and Bi simultaneously, when present at identical concentrations in the DES electrolyte, by carefully choosing the deposition potential. This was confirmed after analysis of the cathodic deposits on Pt and stainless steel (316L) substrates by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS).Experiments with Sb(III) and Cu(II), in addition to Ag(I) and Bi(III) present in the DES electrolyte showed that the cathodic deposition of the different metals appears in the order Ag<Sb<Bi<Cu. Significant co-deposition might occur, enhanced by favourable alloy formation, when metallic elements may deposit at activities lower than 1. Still, at 10 mM of each of the four metal salts present in the DES electrolyte, it was possible to obtain deposits with one, two, three or four metals present, by choosing the proper cathodic deposition potential.AcknowledgementsThis project has received funding from the EU’s Horizon 2020 research and innovation program under Grant Agreement 815748. The content in this presentation reflects only the views of the authors. The European Commission is not responsible for any use that may be made of the information it contains.

Performance of Selective Plated Copper Coatings on Stainless Steel 316L and Nickel Alloy Ni201: Microstructure, Microhardness, Wear Resistance, and Corrosion Resistance

This study investigates the properties and performance of selective plated copper coatings on stainless steel 316L and nickel alloy Ni201 substrates, using acidic and alkaline electrolyte solutions. The analysis encompasses surface microstructure, elemental distribution, microhardness, surface roughness, wear resistance, and corrosion resistance of the coatings. The results demonstrate that the selective plated copper coatings exhibit a uniform and continuous deposition, free from visible irregularities or structural imperfections. Notably, the alkaline copper coatings exhibit significantly higher microhardness values compared to the acidic coatings, irrespective of the substrate materials. Surface roughness measurements reveal an increase in roughness after wear testing for all coatings, with the alkaline coatings showing lower initial roughness values and superior wear resistance compared to the acidic coatings. Concerning corrosion resistance, the alkaline copper coatings display a higher susceptibility to corrosion compared to the acidic coatings. Generally, the findings underscore the effectiveness of the selective plating process in producing high-quality, uniform, and defect-free copper coatings on stainless steel and nickel alloy substrates.

Nanomechanical surface properties of co-sputtered thin film polymorphic metallic glasses based on Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu

Metallic glasses are amorphous materials that have shown prospects in several applications including biomedical due to their superior and unique mechanical, tribological, and bioactive properties. New functional coatings of thin film polymorphic metallic glasses (Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu) were deposited by co-sputtering of constituents from high purity (99.9%) targets. The thin film metallic glasses were deposited on stainless steel 316 L (SS316L) and titanium alloy (Ti) substrates. Co-sputtering offers tuneable parameters (pressure, power, and time), which fosters high-quality polymorphic films of desired thickness and composition. Surface and nanomechanical properties of the films, including surface morphology, structure, mechanical, and tribological properties were investigated using SEM, AFM, XRD, XPS, nanoindentation, and scratch test. The coated substrates exhibit uniform nanostructured films with surface roughness in the range of 1.5 to 7 nm. The XRD spectra show a dominant amorphous glassy polymorphic feature on both substrates with crystallites size in the range of 65–108 nm. Nanomechanical characteristics of the films suggest high wear resistance with film adhesion strength ranging between 624 - 2159 µN and 2273 - 2978 µN on SS316L and Ti substrates, respectively. Overall, these polymorphic Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu nanostructured uniform films with low surface roughness and high adhesion on SS316L and Ti substrates are potential functional surfaces for biomedical applications.

Interlayer machining effects on microstructure and residual stress in directed energy deposition of stainless steel 316L

Powder-based directed energy deposition is one of the major additive manufacturing processes for producing and repairing large-size and high-value metallic components. Due to the rough surface finish and low dimensional accuracy, DED products require post-build machining. Accordingly, the effects of post-machining on build properties is an emerging and important field of research. To date, most of the reported machining cases have been performed after the entire build’s completion, even though interlayer machining may be applied due to design modification or to achieve improved deposition control on localized regions of high curvature. Therefore, in this work, for the first time, the influence of interlayer machining on the processing–structure–properties relationships in powder-based directed energy deposition of stainless steel 316L is investigated. Four types of single-track builds are manufactured on stainless steel 316L substrates: single-layer, double-layer, machined single-layer, and double-layer with interlayer machining. The effects of interlayer machining on the microstructure and residual stress before and after the second layer’s deposition are studied via metallographic imaging and neutron diffraction. In single-layer samples, due to induced plastic strains and heat generated during the machining operation, the microstructure reveals dynamic recrystallization, exhibited by smaller, more equiaxed grains. In the double-layer samples, interlayer machining leads to considerable variation in the microstructure, with grains oriented almost parallel to the scan direction. The interlayer machining also results in greater tensile residual stresses near the interface between the two deposited layers. Findings of this work reveal that interlayer machining has significant effects that should be considered in the design and control of processing–structure–properties–performance relationships in directed energy deposition.

The Effect of Atomization Force on the Structural Properties of NiTi Thin Films

A study using a pulsed laser deposition (PLD) technique was accomplished by growing NiTi nanoparticles on glass and stainless steel 316L substrates. The effects of laser energy state of deposition on the granule size of the NiTi nanoparticle and the structural properties of its thin film were discussed. X-ray diffraction analyses revealed that the films prepared at 65[Formula: see text]W, 75[Formula: see text]W, 85[Formula: see text]W, 100[Formula: see text]W exhibited amorphous structures. AFM results confirmed that the thin films consist of evenly distributed spherical particles. The results also showed an exponential increase in those particles’ sizes.

Synthesis of bio-nanocomposite coating (silver-multi wall carbon nano tubes) by electroless plating method

Silver-multi wall carbon nanotube (Ag-MWCNTs) nano-composite coating was prepared using electroless deposition technique on stainless steel (316L) sheets. Majority of the literature and researches on this issue focuses on the macro and microscale effects of the bath composition as well as process parameters upon the composite coatings microstructure. So far, few researches have studied the bath composition influence upon the structure of phase, microstructure, and surface morphology; therefore, the current investigation compared the influences of the MWCNTs nanoparticles incorporation at various concentrations (0.1, 0.3, and 0.5 g/l) on the phase structure, microstructure and surface morphology. The phase structure changes were evaluated via X-ray Diffraction (XRD) analysis. The surface morphology (nanoparticles distribution into silver coating) was investigated via Scanning Electron Microscopy (SEM). The chemical composition of the nano-composite coating surface was studied via EDS analysis. In the present work, electroless deposition technique was used successfully in synthesis of silver-based MWCNTs nano-composite, so the EDS results showed that the main elements of the nano-composite coating are carbon, silver and oxygen that are distributed homogeneously over the surface of samples, while the SEM analysis results showed the coating is uniform and covers the stainless steel 316L substrate, also that the distribution of MWCNTs nanoparticles into the Ag matrix coating is more uniform. The XRD analysis results manifested the composition and crystal structure of the nano-composite coating consisted of Ag and MWCNTs fully crystalline structure.

Mechanical properties, electrochemical performance and interfacial contact resistance of as-deposited and annealed NbxAlyC and CrxAlyC coatings on stainless steel 316L substrates

NbxAlyC and CrxAlyC coatings (where x is the Nb or Cr target current and y is the Al target current) were deposited on stainless steel 316L substrates using a radio frequency unbalanced magnetron sputtering system. The sputtered NbxAlyC and CrxAlyC coatings were vacuum annealed at 800°C and 750°C for 1 h, respectively. The cross-sectional and surface morphologies of the as-deposited coatings showed a columnar structure and a loose surface, respectively. The X-ray diffraction results showed that the annealed NbxAlyC and CrxAlyC coatings contained Nb2AlC and Cr2AlC MAX crystalline phases, respectively, The MAX crystalline phase improved the hardness, corrosion resistance, and electrical conductivity of the coatings. The annealed coatings also formed an Al2O3 layer with a small cluster size and a dense surface, which significantly improved the corrosion resistance compared to that of the as-deposited coatings. The electrochemical test results showed that the corrosion current density (Icorr) and interfacial contact resistance (ICR) values of all the annealed coatings were lower than those of the as-deposited coatings and were consistent with the standard for the bipolar plates in commercial proton exchange membrane fuel cells. Among all the coatings, the annealed Nb2.5Al0.5C-H coating showed the lowest Icorr and ICR values.

Effect of deposition temperature on the microstructure and tribological properties of Si-DLC coatings prepared by PECVD

The tribological properties of diamond-like carbon (DLC) coatings were influenced by their microstructure, which was controlled by the preparation technology and parameters. In this study, Si-DLC coatings were prepared on cemented carbide (YG10C) and stainless steel (316L) substrates by plasma enhanced chemical vapor deposition with various deposition temperatures. The effect of the deposition temperature on the microstructure and tribological properties was systematically investigated. The results showed that the sp3/sp2 values and hardness of the Si-DLC coatings increased firstly and then decreased as the deposition temperature increased from 60 °C to 180 °C, while the tendency in toughness, adhesion strength and residual stress is not consistent with it. The performance of the coatings obtained at 120 °C was best, while the coatings obtained at 150 °C had the lowest toughness due to the volume expansion caused by the transformation of sp3 to sp2. A graphite transfer layer was observed on the wear tracks of friction pairs. Thereinto, O-Si-C on the transfer layer could further reducing shear resistance and plays a role as a lubricant. Therefore, the coating prepared at the preferred deposition temperature had excellent tribological properties.

Deposition, microstructure and nanoindentation of multilayer Zr nitride and carbonitride nanostructured coatings

Nitrides, carbides, and carbonitrides of transition metal elements like Zr, W, Ti, etc. are generally employed to produce hard coatings. Zirconium-based hard coatings have shown useful applications in the areas of tribology, biomedicine and electrical due to their high thermal stability, hardness, biocompatibility, good erosion, wear, and corrosion resistance. In this study, we created homogeneous and tenacious nanostructured hard coatings based on Zr with good mechanical properties. The magnetron sputter deposition technique was utilized to coat stainless steel 316L substrates with multilayers of Zr/ZrN and ZrN/ZrCN with individual layer thicknesses of 250 and 500 nm for each coating composition. The deposition conditions were adjusted to create two different coating thicknesses of 2 and 3 µm. The thickness of the coating was confirmed using Calotest and the coatings’ morphology and elemental composition were determined utilizing the atomic force microscope and scanning electron microscope equipped with energy dispersive x-ray spectrometer. Coating thickness and adhesion were measured using cross-sectional samples and XRD was utilized to analyze the coatings structure. Nanoindenter was employed to determine the instrumental nanoindentation hardness and elastic modulus. The influence of coating thickness on tribological behavior was further investigated using the ratio of nanohardness-to-elastic modulus (H/E). No evidence of decohesion was observed at the substrate/coatings interface, and the grains of all the coatings were observed to show columnar growth which were homogeneous, compact and dense. The grains of the ZrN/ZrCN coatings were observed to be denser, finer and more compact compared to those of the Zr/ZrN coatings. Correspondingly, higher hardness, modulus and H/E values were exhibited by ZrN/ZrCN than Zr/ZrN coatings. This suggests that the ZrN/ZrCN coatings are capable of exhibiting better wear resistance and fracture toughness. The coatings developed in this investigation are anticipated to be suitable for applications in tribology due to their excellent hardness and H/E properties.

Electrophoretic deposition of chitosan reinforced baghdadite ceramic nano-particles on the stainless steel 316L substrate to improve biological and physical characteristics

Despite the low cost and high mechanical properties of stainless steel (SS 316L) as orthopedic implants, it shows poor bioactivity and biocompatibility due to various corrosion mechanisms occurring in a biological environment. Therefore, this study is aimed at developing a novel nano-composite of chitosan-baghdadite nano-particles by electrophoretic technique to enhance the corrosion resistance, biocompatibility, and bioactivity properties of SS 316L implants. The results demonstrated that the applied Chitosan coating including 1 wt% baghdadite nano-particles at 15 V and 10 min was hydrophobic (44.26° ± 1.34) and it increased the roughness of SS 316L from 0.20 ± 0.01 μm to 1.47 ± 0.22 μm. Furthermore, increasing the baghdadite percentage affected coating adhesion. The evaluation of MG63 cell viability, spreading, and attachment verified no cytotoxicity, and well spreading and suitable attachment of MG63 cells on the coatings (optimum sample = coating with 1 wt% baghdadite nano-particles). This type of coating could provide appropriate biological properties for orthopedic implants based on the observed results.

Microstructure and Corrosion Behavior of Atmospheric Plasma Sprayed NiCoCrAlFe High Entropy Alloy Coating.

High entropy alloys (HEAs) are multi-elemental alloy systems that exhibit a combination of exceptional mechanical and physical properties, and nowadays are validating their potential in the form of thermal sprayed coatings. In the present study, a novel synthesis method is presented to form high entropy alloy coatings. For this purpose, thermal sprayed coatings were deposited on Stainless Steel 316L substrates using atmospheric plasma spraying technique with subsequent annealing, at 1000 °C for 4 h, to assist alloy formation by thermal diffusion. The coatings in as-coated samples as well as in annealed forms were extensively studied by SEM for microstructure and cross-sectional analysis. Phase identification was performed by X-ray diffraction studies. The annealed coatings revealed a mixed BCC and FCC based HEA structure. Potentiodynamic corrosion behavior of SS316L sprayed as well as annealed coatings were also carried out in 3.5% NaCl solution and it was found that the HEA-based annealed coatings displayed the best corrosion resistance 0.83 (mpy), as compared to coated/non-annealed and SS 316 L that showed corrosion resistance of 7.60 (mpy) and 3.04 (mpy), respectively.

Ni-based coating protection of 316L stainless steel at dry, elevated temperature and wet sliding condition

The NiCrSiB coatings are used extensively for wear and oxidation resistance in numerous applications like hot forming industries, power generation plants, petroleum refining, and nuclear power plants. In this paper, NiCrSiB powder deposited by APS (atmospheric plasma spray) and HVOF (high velocity oxy-fuel) process on stainless steel 316L substrate was investigated for the friction and wear at RT (room temperature), 700 °C, at the lubricating condition with clean and contaminated oil with nano alumina particles. The sliding wear tests were carried out on standard tribometer against silicon nitride (1580 HV0.3) counter material following ASTM G99 standard. The coatings characterization was performed using porosity analysis, nano-indentation, 3D non-contact analysis, EDX (energy-dispersive X-ray), SEM (scanning electron microscope) and LRS (Laser Raman Spectrum). The wear, friction and the wear mechanisms were investigated for both coatings at tested conditions. Although the coating wear was substantially affected by the temperature, the specific wear rate of the APS and HVOF coatings lies in the range 10-4 to 10-5 mm3/N.m and hence serviceable up to 700 °C. The coating's wear mechanisms at elevated temperature were a combination of adhesive and tribo-oxidative wear. At the dry, wet, and high-temperature condition, the HVOF coating retains higher wear resistance than APS coating, due to the high dense structure, low porosity, low inflight oxidation and high nano hardness. The nano alumina particles in the contaminated oil reduces the COF significantly for HVOF coating whereas, negligible change in COF has been observed for APS coating.

A study of the electrophoretic deposition of polycaprolactone-chitosan-bioglass nanocomposite coating on stainless steel (316L) substrates

In this research, bioglass nanoparticles were synthesized via sol-gel method and a polycaprolactone-chitosan-bioglass nanocomposite coating was formed on SS316L substrate using electrophoretic deposition method. Then, the effects of voltage and deposition time on morphology, thickness, roughness, and wettability of final coating were investigated. Finally, biocompatibility and toxicity of the coating were evaluated. The results showed that increase of both time and voltage enhanced the thickness, roughness, and wettability of coating. Also, increase of deposition time increased the agglomeration. Therefore, it can be concluded that voltage of 20 V and time of 10 min are suitable for the formation of a uniform agglomerate-free coating. The presence of bioglass nanoparticles also led to the increase of roughness and improvement of polycaprolactone hydrophobicity. The results also showed higher bioactivity in polycaprolactone-chitosan-1% bioglass nanocomposite coating sample. This sample had a roughness ( Ra) of 1.048 ± 0.037 μm and thickness of 2.54 ± 0.14 μm. In summary, the results indicated that coating of polycaprolactone-chitosan-bioglass nanocomposite on SS316L substrate could be a suitable surface treatment to increase its in vivo bioactivity and biocompatibility.

Structural, Mechanical, and Decorative Properties of Sputtered TiN and Ti (N, C) Films for Orthodontic Applications; an In Vitro Study.

In this paper, we explore and modify the structural, mechanical, and decorative properties of films composed by TiN and Ti (N, C) with a wide range of N2 gas flow during the deposition in order to be used on orthodontic systems. The films were grown using reactive DC magnetron sputtering from a pure Ti target and customized with C pellets onto Si and stainless steel 316L substrates. The structural properties were studied using X-ray diffraction and scanning electron microscopy, while the mechanical ones were obtained through hardness, elastic modulus, and friction coefficient. Moreover, the wear rate has been measured under an artificial saliva medium to simulate the oral cavity. The color of the films deposited onto stainless steel 316 L substrate was characterized through CIELab color code. Our findings show that the addition of N2 and C in the Ti matrix improves the mechanical properties of the films. With the increase in the amount of N2 and C, the hardness reaches a value of 739 HV, higher than the one reported in the literature (600 HV), a low value of the coefficient of elasticity (8.0 GPa), and also a low friction coefficient (0.30). Moreover, with the addition of N2 and C in the Ti films, the color of the films changes from metallic aspect until “with” gold, which means that our coatings exhibit versatile mechanical and color characteristics to be used in orthodontic wires applications.

Adhesion study of biocompatible polyhedral oligomeric silsesquioxane - Poly(carbonate-urea) urethane coating on Stainless Steel 316L in the presence of an amino-silane primer

One of the challenges of using Stainless Steel 316L (SS316L) as an implant substrate is poor adhesion of organic/inorganic coatings on their surface. Poor adhesion of the provided coating may lead to serious problems like blockage of arteries in cardiovascular stents. In this study, the (3-aminopropyl) triethoxysilane effect as an adhesion promoter between the organic/inorganic polyhedral oligomeric silsesquioxane - poly(carbonate-urea) Urethane (POSS-PCU) coating and substrate was investigated. The objective was to study the significant parameters, including the surface preparation method, pH of the silane layer, and the curing process on adhesion of the coating on the SS316L.Contact angle measurements indicated that the higher surface free energy values attributed to the pretreated silane layer did not result in better adhesion strength of POSS-PCU coating. Scanning Electron Microscope/Energy Dispersive Using X-Ray and Atomic Force Microscopy results revealed that more uniformity was obtained in silane layers prepared at pH= 4 (acidic solution) compared to higher pH values. The ellipsometry results showed that the acidic silane solution, which was cured at high temperature, had a lower thickness than other primer layers. Lap-shear strength results confirmed a noticeable increase in the adhesion strength of POSS-PCU coating on the SS316L substrate in the presence of the silane layer in dry and wet conditions.

Microstructural characterization and mechanical integrity of stainless steel 316L clad layers deposited via wire arc additive manufacturing for nuclear applications

AbstractThe potential applications of stainless steel 316L components using wire arc additive manufacturing offers many benefits such as improved part complexity, higher deposition rate and less material waste. Microstructural examination indicates the strong interlayer bonding between cladded layers and was mainly austenitic with columnar and equiaxed dendrites while equiaxed grains with annealing twins were observed in the stainless steel 316L substrate. In the current study, we report that stainless steel 316L additively cladded via wire arc additive manufacturing exhibits a 11 % and 14 % increase in the yield strength and tensile strength, correspondingly in contrast to the stainless steel 316L substrate. The enhanced mechanical properties are attributed to the columnar structure and interlayer remelted peritectic growth. Hardness values were higher at the cladded layers compared to the interface and substrate. Interface sample failed in the substrate side and all samples exhibited ductile mode of fracture with fine dimples and micro voids. Wire arc additive manufacturing process can be employed for producing or repairing components with better mechanical properties and corrosion performance for elevated temperature environments including nuclear reactor applications.

Post-annealing effect on the electrochemical behavior of nanostructured magnetron sputtered W3O films in chloride- and acid-containing environments

In this study, magnetron sputtered tungsten oxide (W 3 O) thin films were deposited on stainless steel 316L substrates followed by annealing treatment at different temperatures (200 to 800 °C). The synthesized films were characterized and thereafter investigated for their corrosion resistance behavior, in both 3.5% NaCl and 0.5 M H 2 SO 4 environments, using electrochemical corrosion techniques. FESEM, XRD, and XPS analyses revealed that the oxygen content increases with annealing temperature, which then results in morphological and microstructural changes from cubic nanorods to monoclinic nanoplatelets and nanopyramids, composing of mixed oxidation states (WO 2.72 and WO 2.92 ). Electrochemical impedance and potentiodynamic measurements showed that in the chloride-containing solution the resistance increases with the annealing temperature until an optimum temperature of 400 °C. Similarly, the as-deposited and the films annealed at temperatures up to 400 °C demonstrated better protectiveness that exceeds 95%, in the acidic environment. The passive current densities and the pitting potentials of the films were likewise improved in both environments. Findings in this investigation suggest that an annealing temperature of 400 °C induced optimum protective barrier properties to the film. • Magnetron sputtered W 3 O films were fabricated on 316L stainless steel substrates. • Post-annealing effect at different temperatures on corrosion behavior was assessed. • This results in structural changes from cubic nanorods to monoclinic nanopyramids. • Corrosion and pitting resistance of the films in 3.5%NaCl and 0.5MH 2 SO 4 is improved. • Annealing at 400 °C induced optimum corrosion resistant properties to the W 3 O film.

The role of scanning velocity on laser cladding of NiTi alloy onto stainless steel 316L substrate

In this research, Ni50.8Ti49.2 pre-alloyed powder was used to produce NiTi shape memory alloy coating onto stainless steel 316L substrate. Micro direct metal deposition (μDMD) process was employed to produce coatings with the thickness of 200 μm. To investigate the effect of scanning velocity and the capability of the process, three different coatings were fabricated with three scanning velocities. The effects of scanning velocity variations were investigated by scanning electron microscopy and X-ray diffraction. The results revealed that a good and precise coating can be fabricated when the scanning velocity and the laser power are 200 mm/min and 25 W, respectively, while with the scanning velocity of 120 mm/min, crack formation is inevitable, and with the scanning velocity of 150 mm/min, it would be difficult to achieve a coating with accurate thickness of 200 μm.

Phosphor thermometry for nuclear decommissioning and waste storage

Reliable surface thermometry of stored nuclear waste containers is essential for both health monitoring and corrosion modelling. In this paper we investigate the feasibility of using phosphor thermometry for long-term temperature monitoring of nuclear waste containers and storage racks. Two strands of research were conducted. Firstly, two thermographic phosphors (ruby and manganese-doped magnesium fluorogermanate [MFG]), mixed with six different binders were coated onto stainless steel (316L) substrates and exposed for one month to gamma radiation (γ-ray) and sodium hydroxide (NaOH) solution. Secondly, a hybrid fibre-optic phosphor thermometer, capable of measuring these samples, was constructed and tested. The instrument can measure temperatures using both the luminescence decay time and intensity ratio techniques. Following γ-ray and NaOH exposure, no significant degradation in phosphor appearance or performance was observed. The MFG/silicone binder combination gave the best results. The hybrid phosphor thermometer demonstrated for MFG/silicone binder that:•the intensity ratio technique gave the lowest measurement standard deviation (σ(T) < 0.1 °C) but suffered minor drift with thermal cycling.•the decay time technique (650 nm emission) did not show any drift and was capable of a measurement standard deviation of σ(T) ≤ 0.3 °C.