Heat-treated Substrates Research Articles

Corrosion of an Additively Manufactured Ti6Al4V Alloy in Saline and Acidic Media.

The present work aims to provide corrosion performance data for an additively manufactured Ti6Al4V alloy in saline and polluted environments. The as-received additively manufactured material underwent heat treatment at 850 °C for 3 h to transform the acicular α' microstructure into a lamellar α microstructure. Comparative corrosion assessments were conducted between the heat-treated substrates, the as-received condition, and a conventionally mill-annealed alloy. Potentiodynamic polarization experiments were carried out in saline (3.5 wt.% NaCl) and acid aqueous media ((NH4)2SO4 containing Harrison's solution). The corrosion performance of additively manufactured substrates matched or surpassed that of the conventional alloy in Harrison's solutions while remaining inferior in saline medium, despite forming a thicker passive film. Overall, the XY plane showed better corrosion performance, particularly after the elimination of the acicular α' martensite by the applied heat treatment. The results also suggested that the presence of the coarse β phase was beneficial in 3.5 wt.% NaCl solution and detrimental in Harrison's solutions, more so in acidified and fluorinated conditions.

Hydroxyapatite reinforced surface modification of SS-316L by microwave processing

The current study was focused to modify the surface layer of stainless steel (SS-316L) for enhancing its bioactivity by reinforcing hydroxyapatite (HAp) powder through exploiting the principle of hybrid Microwave Heating (MH) technique. The modified substrates were subjected to post heat-treatment at 400 °C and 700 °C for 1 h. The microstructural analysis of the modified composite layer revealed the existence of HAp particles along with some reaction induced products primarily in the iron-based austenite dendritic matrix. The heat-treated substrates showed a higher microhardness value than that of as-deposited substrates due to densification of the modified layer after heat-treatment. The porosity, surface imperfections and flaws were reduced after heat treatment. The scanning electron microscopy (SEM) images taken over the modified and unmodified SS-316L after immersion test in simulated body fluid showed rapid apatite forming ability on the modified substrates. The apatite growth ability of the modified substrates was reduced after heat treatment performed at 700 °C due to a reduction in the amorphous phase and porosity contents.

Biological control of turfgrass diseases with organic composts enriched with Trichoderma atroviride

The increasing demand of natural products for the control of plant diseases has led to the search for biological control agents, namely fungi, often isolated from composts of organic residues. By composting two different mixes of agro-industrial residues, P1 and P2 composts were obtained, from where a known antagonist, Trichoderma atroviride, was isolated. Later, a second composting process was performed and when the composting mix reached room temperature, the previously isolated T. atroviride was inoculated in both composts to enrich its population (E) and named as P1E and P2E. The suppressive capacity of these two composts against Sclerotium rolfsii, Clarireedia spp. and Rhizoctonia solani was tested two weeks after T. atroviride inoculation, in 100 mL pots with turfgrass seeded with Agrostis stolonifera. The tested treatments were: composts P1 and P2 without any treatment; thermally treated P1 and P2 (P1t, P2t); P1 and P2 enriched without and with previous thermic treatment (P1E, P2E, P1tE, P2tE), and a commercial peat-based substrate, natural (P) and thermally treated (Pt), enriched (PE) and enriched after thermal treatment (PtE). Enriched composts achieved the highest disease control. P1E was more effective in controlling Clarireedia spp.; pots with infected plants grown on P1E, showed 53.5% less affected area compared to P1t. P2E was more effective against R. solani; results showed 69.3% less affected area compared to P2t and both were effective in S. rolfsii control, with a reduction of 38.5% in P1E and 43.5% in P2E. The larger population of Trichoderma spp. observed in the enriched substrates associated to the greater enzyme activity, namely and N-acetyl-β-glucosaminidase, standing out in P2E, will have contributed strongly to the biocontrol of the studied diseases. An increase in some macro and micronutrients was observed in the enriched heat-treated substrates.

Phosphate conversion coatings on 35CrMnSi steels subjected to different heat treatments

Phosphate chemical conversion (PCC) coatings are widely used to improve the corrosion resistance of steels. However, the effects of different substrate heat treatments on the preparation and properties of PCC coatings have rarely been investigated. This research focuses on the influence of rolled (R), normalizing (N), quenching (Q), low-temperature tempering (L-T) and tempering (T) treatments of 35CrMnSi steels on subsequent PCC coating onto these steels. The results showed that the heat treatments played a vital role in coating formation rate, phosphate crystal size and coating anti-corrosion properties. The coating formation rate for heat-treated substrates was as follows: Q>T>L-T>N>R. The order of corrosion resistance of substrates was: R>N>L-T>T>Q. The anti-corrosion resistance of PCC-coated steels after different heat treatments was as follows: T>L-T>Q. The PCC-coated tempered sample offered the best corrosion resistance due to the homogeneous and fine-crystal microstructure of the coating.

Characterization of films fabricated on AZ31 magnesium alloy by heat treatment and immersion methods

Thin films were fabricated on the surface of AZ31 magnesium alloy by heat treatment and subsequent immersion in deionized water or a NaOH solution. In this study, dense films were synthesized during the initial stage of immersion by increasing the (OH)− concentration at the interface of the high-temperature substrate and the solution. The surface of the magnesium substrates was covered by dense films aligned with the surface during the initial stages of immersion. The surface features of these films were different from those of the films formed simply by immersion in aqueous solutions. The cross-sectional results showed that the films formed in a NaOH solution with heat treatment were denser than those grown by DI water immersion with heat treatment. The X-ray photoelectron spectroscopy results revealed that the films fabricated by immersing the heat-treated substrates were mostly composed of MgO and Mg(OH)2 in both the outer and inner layers. Potentiodynamic polarization measurements showed that the films formed by the immersion of heat-treated substrates showed passive regions, and hence could act as passive layers.The morphology and structure of the films were observed by field-emission scanning electron microscopy and transmission electron microscopy. The compositions of the films were investigated using scanning transmission electron microscopy-energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Potentiodynamic polarization measurements were conducted to investigate the corrosion behavior of the films.

Fabrication and characterization of selective laser melting printed Ti–6Al–4V alloys subjected to heat treatment for customized implants design

Selective laser melting (SLM) is a promising technique capable of rapidly fabricating customized implants having desired macro- and micro-structures by using computer-aided design models. However, the SLM-based products often have non-equilibrium microstructures and partial surface defects because of the steep thermal gradients and high solidification rates that occur during the laser melting. To meet clinical requirements, a heat treatment was used to tailor the physiochemical properties, homogenize the metallic microstructures, and eliminate surface defects, expecting to improve the cytocompatibility in vitro. Compared with the as-printed Ti–6Al–4V substrate, the heat-treated substrate had a more hydrophilic, rougher and more homogeneous surface, which should promote the early cell attachment, proliferation and osseointegration. More importantly, a crystalline rutile TiO2 layer formed during the heat treatment, which should greatly promote the biocompatibility and corrosion resistance of the implant. Compared to the untreated surfaces, the adhesion and proliferation of human bone mesenchymal stem cells (hBMSCs) on heat-treated substrates were significantly enhanced, implying an excellent cytocompatibility after annealing. Therefore, these findings provide an alternative to biofunctionalized SLM-based Ti–6Al–4V implants with optimized physiochemical properties and biocompatibility for orthopedic and dental applications.

SEM/EDS investigation of one-step flame sprayed and fused Ni-based self-fluxing alloy coatings on steel substrates

This study presents the results of light optical and scanning electron microscopy as well as energy dispersive spectroscopy investigation of the Ni-based self-fluxing alloys (NiCrBSi, NiCrWBSi and NiCrBSi + WC) deposited on steel substrates (heat treated carbon steel C45, heat treated low-alloyed steel 42CrMo4 and austenitic stainless steel X6CrNiMo18-10-2) by one-step flame spraying and fusing process. The microstructure of coatings and coating/substrate interface but also the effects of deposition technology on the heat-treated steel substrates which have frequently been used in practice were investigated. The influence of the sample size on the microstructure was also discussed. A proof is given of the change in the structure of coating, coating/substrate interface and substrate due to high fusing temperature, depending on type of steel substrate (and relating thermal properties), coating thickness but also on dimensions of the sample.

Effect of heat treatment on the characteristics of tool steel deposited by the directed energy deposition process

The directed energy deposition process has been mainly applied to re-work and the restoration of damaged steel. Differences in material properties between the base and the newly deposited materials are unavoidable, which may affect the mechanical properties and durability of the part. We investigated the effect of heat treatment on the characteristics of tool steel deposited by the DED process. We prepared general tool steel materials of H13 and D2 that were deposited onto heat-treated substrates of H13 and D2, respectively, using a direct metal tooling process. The hardness and microstructure of the deposited steel before and after heat treatment were investigated. The hardness of the deposited H13 steel was higher than that of wrought H13 steel substrate, while that of the deposited D2 was lower than that of wrought D2. The evolution of the microstructures by deposition and heat treatment varied depending on the materials. In particular, the microstructure of the deposited D2 steel after heat treatment consisted of fine carbides in tempered martensite and it is expected that the deposited D2 steel will have isotropic properties and high hardness after heat treatment.

Growth of TiO2 Nanotube Layers on Ti Substrates with Different Microstructures

The present work examined the morphology of anodic oxide layers on Ti substrates with different microstructures. The microstructures were varied by the heat-treatment or accumulative roll-bonding (ARB) process. Tubular oxide layers were formed on all Ti substrates by anodization, but the thickness of the layers was changed. The thickness of oxide layer formed on heat-treated substrates decreased with increasing heat-treatment temperature and duration. On the other hand, ARB process resulted in the increase of the thickness. Therefore, the microstructures affected the growth of tubular anodic oxide layers.

ChemInform Abstract: Sonochemical Synthesis and Characterization of Iron Oxide Coated on Submicrospherical Alumina: A Direct Observation of Interaction Between Iron Oxide and Alumina.

Coating of iron oxides on submicrospheres of alumina was carried out by the sonochemical method. Three kinds of alumina were used, namely, the as-prepared, 700 and 1000 °C heated-alumina. TEM results reveal various coating effects on different heat-treated substrates. The optimum coating is obtained on as-prepared amorphous alumina, in which most of the iron oxide particles are adhered to alumina spheres tightly, while in the sample coated on crystallized alumina heated at 1000 °C, most of the iron oxide particles remain separate from the alumina spheres. The strong interaction between iron oxides and alumina substrate was directly observed by XRD, TEM, and IR and magnetic measurements. Owing to the strong interaction between adhered iron particles and alumina substrate, the complete transformation of γ-Fe2O3 to α-Fe2O3 was retarded to higher than 700 °C; conversely, the presence of haematite can induce the formation of α-Al2O3 at the high temperatures. TEM images clearly show the changes of particle size...

Characterization and in vitro evaluation of biphasic calcium pyrophosphate–tricalciumphosphate radio frequency magnetron sputter coatings

The objective of this study was to characterize the physicochemical, dissolution, and osteogenic properties of radio frequency magnetron sputtered dicalcium pyrophosphate/tricalciumphosphate (Pyro/TCP) and hydroxylapatite (HA) coatings. Therefore Pyro/TCP and HA coatings were deposited on grit-blasted titanium discs. The results showed that the deposited coatings were amorphous and changed into a crystalline structure after IR heat-treatment of 550 degrees C for HA and 650 degrees C for Pyro/TCP. Heat-treated HA coatings appeared to be stable during immersion in simulated body fluid (SBF), that is no changes in the XRD pattern were observed. Also, no dissolution of the coating was observed by scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) revealed that the Ca/P ratio of the HA coatings remained constant during SBF immersion. On the other hand, the heat-treated Pyro/TCP coatings showed a surface reaction of calcium pyrophosphate into a beta-tricalcium phosphate phase during SBF immersion. This was confirmed by EDS analysis. Rat bone marrow-derived osteoblast-like cells cultured on the heat-treated substrates showed that cell proliferation and differentiation occurred on both types of bioceramic coatings. No significant differences for proliferation and early differentiation were observed between cells cultured on heat-treated Pyro/TCP and HA at individual time points. However, osteocalcin expression, a late marker for osteoblast-like cell differentiation, was significantly increased after 12 days of culture on HA-coatings. These results were confirmed by SEM observations and suggest increased osteogenic properties for HA-coatings over Pyro/TCP-coatings. Additional research is necessary to obtain conclusive evidence on the in vivo osteogenic capacity of Pyro/TCP coatings.

Ultrahigh-Surface-Area Anatase Thin Films by Direct Oxidation of Ti Film with Hydrogen Peroxide

Nanostructured titania films are formed by directly oxidizing titanium with hydrogen peroxide. A low-temperature anneal transforms the films from an amorphous phase to anatase crystal. Surface-area measurements of the annealed nanostructured titania using the Brunauer, Emmett, and Teller method reveal a specific surface area of 535 m 2 /g, the highest ever reported for a nanostructured titania film. The low-temperature anneal is compatible with heat-treated polyimide or polyester substrates for roll-to-roll processing of flexible electronics or solar cells.

The Heat Treatment Characteristics of Hydroxyapatite Thin Films Deposited by RF Sputtering

【RF sputtering process was applied to produce thin hydroxyapatite(HAp) films on Ti-6Al-4V alloy substrates. The effects of different heat treatment conditions on the hardness between HAp thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the Ti-6Al-4V alloy substrates were heat treated for 1h at $850^{\circ}C\;under\;3.0{\times}10^{-3}torr$ , and after deposition, the HAp thin films were heat treated for 1h at $400^{\circ}C,\;600^{\circ}C\;and\;800^{\circ}C$ under the atmosphere, and analyzed FESEM-EDX, FTIR, XRD, nano-indentor, micro-vickers hardness, respectively. Experimental results represented that the surface defects of thin films decreased by relaxation of internal stress and control of substrate structure followed by heat treatment of substrates before the deposition, and the HAp thin films on the heat-treated substrates had higher hardness than none heattreated substrates before the deposition, and the hardness properties of HAp thin films and Ti-6Al-4V alloy substrates appeared independent behavior, and the hardness of HAp thin films decreased by formation of $VTiO_3(OH),\;{\theta}-Al_{0.32}V_2O_5,\;Al_{0.33}V_2O_5$ .】

The corrosion behaviour of manganese phosphate coatings applied to AISI 4140 steel subjected to different heat treatments

This paper aims to investigate the corrosion behaviour of manganese phosphate coatings on AISI 4140 after various heat treatments. Prior to coating, quenching and tempering treatments were applied to the substrates prepared for this process. The structural and mechanical properties of nonheat-treated and heat-treated substrates were determined using hardness test, optical microscope, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The changes of hardness, microstructure and phase density of heat-treated substrates before the coating were also observed. Manganese phosphate coatings were applied to heat-treated substrates in a coating bath at a temperature of 90 °C, and electrochemical polarisation measurements of the phosphate-coated substrates were carried out. It was observed that the corrosion potential of manganese-phosphate-coated substrates, which followed the quenched treatments, were higher than that of the tempered substrates. The highest corrosion potential was obtained for the coatings on water-quenched (WQ) substrates. It was found that the heat treatment applied to the substrates yield an important improvement in the corrosion resistance of the coatings on substrates.

Effect of calcium phosphate coating composition and crystallinity on the response of osteogenic cells in vitro.

The aim of this study was to investigate the effect of calcium phosphate coating crystallinity and composition on the proliferation and differentiation of rat bone marrow (RBM) cells. Grit-blasted titanium substrates were provided with thin sputter-coated calcium phosphate (Ca-P) films of different composition. The Ca-P-coated substrates were used as-sputtered or were heat-treated. XRD measurements showed that the as-sputtered coatings had an amorphous structure, whereas the heat-treated substrates showed an amorphous-crystalline structure. RBM cells were cultured on these substrates and on noncoated titanium substrates. After specific culture times, the expression of osteogenic markers by the cells was studied. On the amorphous-crystalline coatings as well as on titanium substrates, RBM cells proliferated, expressed alkaline phosphatase and showed mineralization. More mineralization was found on the amorphous-crystalline coatings than on the titanium substrates. Some precipitation was also found on substrates that were incubated in complete culture medium without cells. This precipitate disappeared after prolonged incubation. Alkaline phosphatase expression differed on the various amorphous-crystalline Ca-P-coated substrates, but no difference was found in the mineralization on these substrates. The amorphous Ca-P coatings showed extensive dissolution and some signs of precipitation after longer culture periods. Proliferation and differentiation of RBM cells was not seen on the amorphous coatings, regardless of Ca-P composition. We conclude that amorphous-crystalline Ca-P coatings stimulate differentiation of RBM cells, with only limited differences between coatings of various composition. In contrast, Ca-P coatings with an amorphous structure inhibit the growth and differentiation of RBM cells. This effect was found on all amorphous substrates, regardless of Ca-P composition.

Hydroxyapatite-coated Ti–6Al–4V: Part 2: the effects of post-deposition heat treatment at low temperatures

The present investigation explores the effects of a 90-h post-deposition annealing treatment at 400°C in air on the crystallographic and chemical properties of a plasma-sprayed hydroxyapatite (HA) coating, the thickness and composition of the interfacial oxide layer, and the fatigue behaviour of the underlying Ti–6Al–4V substrate. X-ray diffraction analysis revealed that significant recovery of the crystalline HA structure occurred as a result of the treatment, however, as compared with results obtained through treatment at higher temperatures, recovery obtained through use of the present treatment was incomplete. X-ray photoelectron spectroscopy analysis showed no changes in the constituents of the oxide layer, with the oxide species TiO 2, Al 2O 3, V 2O 5, V 2O 3, and VO 2 present on both the as-sprayed and the heat-treated substrates. A change in film thickness was observed, however, as evidenced by a change in colour from opaque bronze to dark purple. The fatigue resistance of the substrate was found to be significantly reduced by the heat treatment, with the lives of heat-treated coupons with coatings of all thicknesses closely resembling those of as-sprayed coupons with thick HA coatings and uncoated stress-relieved coupons presented in Part 1 of this study. Stress relief was identified as the most likely cause of these reductions.

Sonochemical Synthesis and Characterization of Iron Oxide Coated on Submicrospherical Alumina: A Direct Observation of Interaction between Iron Oxide and Alumina

Coating of iron oxides on submicrospheres of alumina was carried out by the sonochemical method. Three kinds of alumina were used, namely, the as-prepared, 700 and 1000 °C heated-alumina. TEM results reveal various coating effects on different heat-treated substrates. The optimum coating is obtained on as-prepared amorphous alumina, in which most of the iron oxide particles are adhered to alumina spheres tightly, while in the sample coated on crystallized alumina heated at 1000 °C, most of the iron oxide particles remain separate from the alumina spheres. The strong interaction between iron oxides and alumina substrate was directly observed by XRD, TEM, and IR and magnetic measurements. Owing to the strong interaction between adhered iron particles and alumina substrate, the complete transformation of γ-Fe2O3 to α-Fe2O3 was retarded to higher than 700 °C; conversely, the presence of haematite can induce the formation of α-Al2O3 at the high temperatures. TEM images clearly show the changes of particle size...

Investigation of Deep Levels in GaP Liquid Phase Epitaxial Layers on Substrates with Vapor Pressure Heat Treatment

AbstractWe fabricated GaP liquid phase epitaxial layers with temperature difference method under controlled vapor pressure (TDM-CVP), successively to GaP substrate annealing at growth temperature (1133K) under various phosphorus vapor pressures around the optimum one (150 torr) for stoichiometric crystallization of GaP. Photocapacitance (PHCAP) and photoluminescence measurements have been carried out for characterizing GaP substrate crystals and the LPE layers and for revealing the mechanism of defect formation. Over one order of magnitude decrease of deep level densities in PHCAP has been observed after substrate crystals are annealed. Compared to the layers on substrates without heat treatment, similar tendency of deep level density deduction has been found in GaP LPE layers on heattreated substrates. In photoluminescence measurements, an obvious decrease of 700nm-band intensity from heat-treated substrates, as well as increases of green band intensities from GaP LPE layers on heat treated substrates, have been observed at 77K. Phosphorus interstitial is suggested to be possibly related to the origin of deep level centers in the GaP substrate crystals. It is considered that during the process of heat treatment at growth temperature, under the optimum phosphorous pressure, the defects in GaP substrate crystals reach an equilibrium state, so that their diffusion to the growth layer decreases greatly.

SEM and EMPA analysis of impurities related to GaAs substrates and MBE grown GaAs layers

Abstract Distribution of impurities on heat-treated GaAs substrates and layers has been investigated by SEM in conjunction with EMPA analysis. The layers were grown by MBE on both undoped and chromium doped semi-insulating substrates. Comparisons of the electron micrographs and the corresponding EMPA spectra suggest that heating causes the impurities, namely Si, Fe and Cr, to diffuse out from the substrate and redistribute themselves on the layer surface resulting in characteristic defect patterns. No effects due to arsenic over-pressure and/or presence of carbon in the growth environment were apparent, as suggested by previous studies.

Low temperature deposition of tribological coatings

The results of microstructural and tribological studies performed on sputterdeposited coatings of ZrO2 20Y2O3, TiB2, and B18 wt pct Si are reported. In each case, deposition parameters were identified that offered good tribological properties while maintaining low deposition temperatures (< 400 °C) to avoid distortion and softening of prior heattreated substrates. Zirconia deposits were prepared with a pronounced columnar microstructure that provided excellent thermal fatigue and wear resistance, making them candidates for heat engine applications. The TiB2 coatings were the hardest coatings prepared. These provided good wear resistance on steel substrates. The BSi coating displayed excellent wear resistance and good adherence to Cu and Al alloys.