Improving mechanical properties and high-temperature oxidation of press hardened steel by adding Cr and Si

This work investigated the effect of Cr and Si on the mechanical properties and oxidation resistance of press hardened steel.Results indicated that the microstructure of the Cr-Si micro-alloyed press hardened steel consisted of lath martensite,M_(23)C_(6)carbides,and retained austenite.The retained austenite and carbides are responsible for the increase in elongation of the micro-alloyed steel.In addition,after oxidation at 930℃for 5 min,the thickness of the oxide scales on the Cr-Si micro-alloyed press hardened steel is less than 5μm,much thinner than 45.50μm-thick oxide scales on 22MnB5.The oxide scales of the Cr-Si micro-alloyed steel are composed of Fe_(2)O_(3),Fe_(3)O_(4),mixed spinel oxide(FeCr_(2)O_(4)and Fe_(2)SiO_(4)),and amorphous SiO_(2).Adding Cr and Si significantly reduces the thickness of the oxide scales and prevents the generation of the FeO phase.Due to the increase of spinel FeCr_(2)O_(4)and Fe_(2)SiO_(4)phase in the inner oxide scale and the amorphous SiO_(2)close to the substrate,the oxidation resistance of the Cr-Si micro-alloyed press hardened steel is improved.

Micro-analysis of high-temperature oxidation-resistance of a new kind of heat-resistant grid plate in grate-kiln

To further improve the oxidation-resistance of materials and reduce the cost of grid plates in grate-kiln, a new kind of heat-resistant grid plate was developed. The microstructure of this grid plate with a life more than 18 months was studied by XRD, SEM and EDS techniques. The results show that high hardness, high intensity and good impact property make the new kind of heat-resistant grid plate and its oxide film have a higher resistance to deformation and abrasion at 900-1000℃ Besides, small grain size is beneficial to form a complete protective oxide film. The oxide film composed of SiO2 layer, Cr2O3 layer and Fe2O3 layer is rather thin and bonds closely with the backing. The forming of the chemical stable nickel-rich layer increases the density of Cr2O3 layer.

High-temperature oxidation behavior of heat resistant stainless steel 1.4828

The kinetic curves of the high-temperature oxidation of austenitic heat resistant stainless steel 1. 4828 at 1 050 ℃ were measured using a weighing method. It is shown that the oxidation curves at 1 050 ℃ followed the parabolic line law, and after 250 h of oxidation, the mass gain was about 80 g/m2. The surface morphology and structure of the oxide layers were studied by scanning electron microscopy and X-ray diffraction. A complicated oxide layer obtained at 1 050 ℃ was mainly composed, from inner to outer, of （FeSi） 3 04, Cr2 03, Fe2 03, and spinel oxides FeCr204 and NiMn204.

OXIDATION RESISTANCE AND MECHANICAL PROPERTIES OF Ti_3Al-Nb-Mo-Si ALLOYS

In the present paper,the development of Ti3Al-Nb-Mo-Si alloys for high oxidation resistance is reviewed.Beside of weight gain of alloys with different Nb and Si addition is tested,the evaluation of comprehensive mechanical properties has been taken,include the room-temperature and 700℃ tensile properties,thermal stability,creep rupture and fracture toughness of the alloys,It has shown that the oxidation resistance and mechanical properties were significantly affected by the variation of Nb and Si contents.The composition with the best balance of properties is Ti-24Al-13Nb-1.5Mo-0.5Si and Ti-24Al-15Nb-1.5Mo,which is mush higher than that of Super,α_2 alloy (Ti-25Al-10Nb-3V-1Mo).

A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid

Three high-temperature resistant polymeric additives for water-based drilling fluids are designed and developed:weakly cross-linked zwitterionic polymer fluid loss reducer(WCZ),flexible polymer microsphere nano-plugging agent(FPM)and comb-structure polymeric lubricant(CSP).A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid was developed for deep drilling.The WCZ has a good anti-polyelectrolyte effect and exhibits the API fluid loss less than 8 mL after aging in saturated salt environment at 200°C.The FPM can reduce the fluid loss by improving the quality of the mud cake and has a good plugging effect on nano-scale pores/fractures.The CSP,with a weight average molecular weight of 4804,has multiple polar adsorption sites and exhibits excellent lubricating performance under high temperature and high salt conditions.The developed drilling fluid system with a density of 2.0 g/cm^(3)has good rheological properties.It shows a fluid loss less than 15 mL at 200°C and high pressure,a sedimentation factor(SF)smaller than 0.52 after standing at high temperature for 5 d,and a rolling recovery of hydratable drill cuttings similar to oil-based drilling fluid.Besides,it has good plugging and lubricating performance.

Effects of Al and N plasma immersion ion implantation on surface microhardness,oxidation resistance and antibacterial characteristics of Cu

A1 and N were introduced into copper substrate using plasma immersion ion implantation （PIII） in order to enhance its hardness and oxidation resistance. The dosage of N ion is 5 × 1016 cm-2, and range of dosage of A1 ion is 5× 1016-2× 1017 cm-2. The oxidation tests indicate that the copper samples after undergoing PIII possess higher oxidation resistance. The degree of oxidation resistance is found to vary with implantation dosage of AI ion. The antibacterial tests also reveal that the plasma implanted copper specimens have excellent antibacterial resistance against Staphylococcus aureus, which are similar to pure copper.

Electrochemical anodic oxidation assisted fabrication of memristors

Owing to the advantages of simple structure,low power consumption and high-density integration,memristors or memristive devices are attracting increasing attention in the fields such as next generation non-volatile memories,neuromorphic computation and data encryption.However,the deposition of memristive films often requires expensive equipment,strict vacuum conditions,high energy consumption,and extended processing times.In contrast,electrochemical anodizing can produce metal oxide films quickly(e.g.10 s) under ambient conditions.By means of the anodizing technique,oxide films,oxide nanotubes,nanowires and nanodots can be fabricated to prepare memristors.Oxide film thickness,nanostructures,defect concentrations,etc,can be varied to regulate device performances by adjusting oxidation parameters such as voltage,current and time.Thus memristors fabricated by the anodic oxidation technique can achieve high device consistency,low variation,and ultrahigh yield rate.This article provides a comprehensive review of the research progress in the field of anodic oxidation assisted fabrication of memristors.Firstly,the principle of anodic oxidation is introduced;then,different types of memristors produced by anodic oxidation and their applications are presented;finally,features and challenges of anodic oxidation for memristor production are elaborated.

Effect of La_2O_3 on microstructure and high-temperature wear property of hot-press sintering FeAl intermetallic compound

FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper.The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic compound,and correspondingly improved the high-temperature wear resistance.SEM and EDS analyses of the wo...

Corrosion evolution of high-temperature formed oxide film on pure Sn solder substrate

The evolution of morphology, composition, thickness and corrosion resistance of the oxide film on pure Sn solder substrate submitted to high-temperature aging in 150 °C dry atmosphere was investigated. The results indicate that high-temperature aging accelerates the dehydration of Sn(OH)_(4)in the pre-existing native oxide film to form SnO_(2)and facilitates the oxidation of fresh Sn substrate, resulting in the gradual increase in oxide film thickness and surface roughness with prolonging aging time. However, the corrosion resistance of the film initially is enhanced and then deteriorated with an extending aging time. Besides, the formation and evolution mechanisms of the oxide film with aging time were discussed.

Oxidation resistance of powder metallurgy Ti-45Al-10Nb alloy at high temperature

TiAl alloy with high Nb content,nominally Ti-45Al-10Nb,was prepared by powder metallurgy,and the oxidation resistance at 850,900,and 950℃was investigated.The high-temperature oxidation-resistance mechanism and oxidation dynamics were discussed following the oxide skin morphology and microstructural evolution analysis.The oxide skin structures were similar for 850 and 900℃,with TiO_(2)+Al_(2)O_(3)mixture covering TiO_(2)with dispersed Nb_(2)O_(5).At 950℃,the oxide skin was divided into four sublayers,from the outside to the parent metal:loose TiO_(2)+Al_(2)O_(3),dense Al_(2)O_(3),dense TiO_(2)+Nb_(2)O_(5),and TiO_(2)matrix with dispersed Nb_(2)O_(5).The Nb layer suppressed the outward diffusion of Ti atoms,hindering the growth of TiO_(2),and simultaneously promote the formation of a continuous Al_(2)O_(3)protective layer,providing the alloy with long-term high-temperature oxidation resistance.

In-situ Synthesis and Oxidation Resistance of Sialon/SiC Composite Ceramics Applied as Solar Absorber

Sialon/SiC composites were synthesized in situ from SiC,α-Si_(3)N_(4),AlN,calcined bauxite,quartz and Y_(2)O_(3) via layered buried sintering at different temperatures (1 540-1 640 ℃).The results showed that the O’-sialon/SiC sample with 60 wt% silicon carbide sintered at 1 600 ℃ exhibited excellent mechanical properties,with apparent porosity of 16.01%,bulk density of 2.06 g·cm^(-3),bending strength of 52.63 MPa,and thermal expansion coefficient of 5.83×10-6 ℃^(-1).The oxide film formed on the surface was linked closely to O’-sialon,so the oxide film was not easily broken.After 100 h oxidization,the sample surface was smoother and denser,with oxidation weight gain rate 23.6 mg/cm^(2) and oxidation rate constant 2.0 mg^(2)·cm^(-4)·h^(-1).Therefore,the sample had the excellent high-temperature oxidation resistance.It was confirmed that the in-situ sialon/SiC composites could be a promising candidate for solar absorber owing to its high-temperature oxidation resistance.

Research on material design and high-temperature friction and wear properties of new graphitic steel

To solve the problem of the severe mismatch between the product and roll materials in the preliminary rolling line,a new graphitic steel material was designed,its microstructure and high-temperature friction and wear properties were investigated.Moreover,the feasibility of replacing semi-steel with this new material in the V1 stand roll was studied herein.The results show that the graphitic steel matrix is strengthened by silicon and nickel elements.The presence of spherical graphite also provides self-lubrication and heat conduction and prevents the propagation of cracks.Carbides in the appropriate amount and size strengthen the matrix,reduce the cracking effect of the matrix,and are not easily broken,thereby reducing high-temperature abrasive wear.Under the same hightemperature friction and wear conditions,compared with semi-steel,the wear-scar surface of graphitic steel exhibits less wear-scar depth and wear volume,a smaller friction coefficient,reduced oxide layer thickness,and fewer instances of peeling and microcracks.Therefore,the newly designed graphitic steel has higher wear resistance and hot-crack resistance than semi-steel,which makes it feasible for use in replacing semi-steel as a new V1 frame roll material in the blooming mill.

Optical and Irradiation-Resistant Properties of ITO Films on F46 and PI Substrates

This study investigated indium tin oxide(ITO) films that were deposited on fluororesin-46(F46) and polyimide(PI) transparent flexible substrates by a DC magnetron sputtering system. The optical properties of ITO films on F46 and PI including transmittance and reflectance in visible, near-infrared, and infrared spectral regions were obtained, and the surface morphology, and optical and electrical properties of ITO/F46 and ITO/PI after vacuum ultraviolet irradiation were investigated. The results showed that the mean transmittances of ITO/F46 and ITO/PI decreased and the sheet resistance increased after the irradiation, and these effects were mainly attributed to the greater surface roughness and crystal defects caused by the irradiation.

Structure and properties of ceramic coatings formed on aluminum alloys by microarc oxidation

The thick and hard ceramic coatings were deposited on 2024 Al alloy by microarc oxidation in the electrolytic solution. Microstructure, phase composition and wear resistance of the oxide coatings were investigated by SEM,XRD and friction and wear tester. The microhardness and thickness of the oxide coatings were measured. The results show that the ceramic coating is mainly composed ofα-Al2O3 andγ-Al2O3. During oxidation, the temperature in the microarc discharge channel is very high to make the local coating molten. From the surface to interior of the coating, microhardness increases gradually. The microhardness of the ceramic coating is HV1800, and the microarc oxidation coatings greatly improve the antiwear properties of aluminum alloys.

Microstructure, mechanical and oxidation characteristics of detonation gun and HVOF sprayed MCrAlYX coatings

Microstructure, mechanical property and oxidation resistance of MCrAlYX coatings prepared by detonation gun (D-gun) and HVOF spraying were investigated. Lamellar microstructure and uniform microstructure formed in D-gun sprayed MCrAlYX coating and HVOF sprayed coating, respectively. Element redistribution and formation of new phase took place during the detonation process. Besides, the porosity of D-gun sprayed coating was much lower than that of HVOF sprayed coating. On the mechanical property, the micro-hardnesses of the two coatings were in the same level (~HV 910). However, D-gun sprayed MCrAlYX coating exhibited larger standard deviation of microhardness due to its lamellar microstructure, and exhibited better bend bonding strength owing to the existence of residual compressive stress between the layers and particles. Meanwhile, due to the much more compact microstructure, D-gun sprayed MCrAlYX coating showed superior oxidation resistance to the HVOF sprayed coating. The continuous dense protective layer can form earlier in D-gun sprayed coating and thus suppress further oxidation and control the oxide thickness at a relatively low level.

Micro and nano-enabled approaches to improve the performance of plasma electrolytic oxidation coated magnesium alloys

Magnesium(Mg)and its alloys have become a hot research topic in various industries owing to the specific physical and chemical properties.However,high corrosion rate is considered the key lifetime-limiting.Plasma electrolytic oxidation(PEO)method is a simple strategy to deposit an oxide layer on the surface of light metals such as magnesium alloys,to control corrosion rate and promote some other properties,depending on their performances.Nevertheless,their features including their micropore size,distribution,and interconnectivity,and microcracks have not been improved to an acceptable level to support long-term performances of the magnesium-based substrates.Studies have introduced micro/nano-enabled approaches to enhance various properties of PEO coatings such as corrosion resistance,tribological properties,self-healing ability,bioactivity,biocompatibility,antibacterial properties,or catalytic performances.These strategies consist of incorporating of micro and nanoparticles into the PEO layers to produce multi-functional surfaces or the formation of multi-layered coatings to cover the defects of PEO coatings.In this perspective,the present paper aims to overview various nano/micro-enabled strategies to promote the properties of PEO coatings on magnesium alloys.The main focus is given to the functional changes that occurred in response to the incorporation of various types of nano/micro-structures into the PEO coatings on magnesium alloys.

Reduced graphene oxide (RGO) reinforced Mg biocomposites for use as orthopedic applications: Mechanical properties, cytocompatibility and antibacterial activity

Magnesium(Mg) has attracted wide interest in orthopedic applications as they exhibit great biodegradability and strong biocompatibility,while corrosion is the main concern for Mg that should be addressed prior to biomedical applications. In this work, ZM31(Mg-3Zn-1Mn)/x RGO(x = 0, 0.5, 1 and 1.5 wt%) biocomposites were synthesized by semi-powder metallurgy method. The results showed that the RGO acting as an effective reinforcing filler to prevent deformation and showed better compressive strength(282.3 ± 9 MPa) and revealed enhancement in failure Strain(7.8 ± 2.1%) at 1 wt% RGO concentration compared to Mg alloy(244.5 ± 9 MPa and 7.1 ± 1.5%respectively). Moreover, fracture analysis indicated a more ductile fracture of the nanocomposites after the incorporation of RGO. Crack bridging, crack deflection and crack branching are dominant mechanisms for reinforcement of Mg-based containing RGO. Mg composites containing 0.5 wt% RGO showed a low corrosion rate(2.75 mm/year), while more incorporation of RGO resulted in an increased corrosion rate(4.38 mm/year). In addition, the degradation rate of ZM31 alloy(2.57 mg·cm-2·d-1) obviously decreased with the addition of 0.5 wt%RGO(1.84 mg·cm-2·d-1) in the SBF. Besides, continuous apatite layers were created on the composites in the SBF solution. Also, the cell culture examinations showed good cell viability and adhesion on composites with 0.5 and 1 wt% RGO, which was demonstrated by the SEM and MTT assay The alkaline phosphatase(ALP) activity of the ZM3–0.5RGO composite was considerably higher than that of ZM31matrix alloy in 24 h and 48 h, implying higher osteoblastic differentiation. The antibacterial behavior toward both bacteria(E. coli and S.aureus) exhibited that escalating RGO concentration in Mg-matrix composites leads to further inhibition of bacteria growth. These findings suggested that ZM31–0.5RGO biocomposite could be a more promising candidate for orthopedic implants.

Remarkable Resistance Change in Plasma Oxidized TiOx/TiNx Film for Memory Application

We report the experimental phenomenon of large resistance change in plasma oxidized TiOx/TiNx film fabricated on W bottom-electrode-contact （W-BEC） array. The W-BEC in diameter 26Ohm is fabricated by a 0.18μm CMOS technology, and the TiOx/TiNx cell array is formed by rf magnetron sputtering and reactive ion etching. In current-voltage （I- V） measurement for current-sweeping mode, large snap-back of voltage is observed, which indicates that the sample changes from high-resistance state （HRS） to low-resistance state （LRS）. In the I-V measurement for voltage-sweeping mode, large current collapse is observed, which indicates that the sample changes from LRS to HRS. The current difference between HRS and LRS is about two orders. The threshold current and voltage for the resistance change is about 5.0- 10^-5 A and 2.5 V, respectively. The pulse voltage can also change the resistance and the pulse time is as shorter as 30 ns for the resistance change. These properties of TiOx/TiNx film are comparable to that of conventional phase-change material, which makes it possible for RRAM application.

Effects of Scale Composition on Oxidation Kinetics of Fe-based Superalloy

By oxidation weight gain method, four groups of Fe-based superalloys with different content of chromium, aluminium and silicon were tested at 1 200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted, and the equations were regressed by least square method and non-linear curve fitting. The effects of different scale compositions on the morphology and oxidation kinetic law were studied further by analysis of X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the compounded scale is composed of Cr2O3, Al2O3, SiO2 and FeCr2O4, with compact structure and fine grains, possessing complete oxidation resistance at 1 200 ℃, and the oxidation kinetic curve follows the power function of y=axb （a0, 0b1）. When the compounded scale lacks Al2O3 or SiO2, it becomes weak in oxidation resistance, but the oxidation kinetic curve still follows the power function with bigger parameter b. When Cr2O3 is absent, the kinetic curve shows two parts： the slow adding of oxidation weight gains at the beginning and the ascending line in the end. Such scale loses oxidation resistance completely.

Experimental analysis of HR-120 alloy used for high-temperature fans

High-temperature circulating fans blow 800 ℃ HN protective atmosphere to the surface of the strip as a jet heating power source or suspending source,playing a core role in metal strip continuous annealing furnaces. In this study,several high-temperature alloys were experimentally compared based on their high-temperature mechanical properties,high-temperature creep resistance,and high-temperature oxidation resistance. The results indicate that though the price of HR-120 alloy is only half of Inconel 601,it is suitable for the manufacture of fans that can withstand a high temperature of 800 ℃ given its good creep resistance,high-temperature oxidation resistance,and price advantage.