Preparation of TiO2 Coatings on Carbon Fibers

Carbon fibers have been TiO2 coated. Previously, the carbon fiber surface has been heat-treated to remove the sizing. The TiO2 layer has been formed on the fiber surface using the sol-gel technique by immersion in a solution. After coating, the samples have been dried at room temperature and annealed at 500 °C in air for 30 minutes. The phase composition of the coating obtained has been studied using X-ray diffraction. X-ray diffraction analysis of the coating and sol has shown that the rutile phase and the average size of TiO2 crystallites grow with an increase in the annealing temperature. The results of studying TiO2 coating antioxidative properties within 500-800 °C are given. Studying the morphology of the TiO2 coating on the fiber surface and the burnout rate (weight change) have shown that the coating exhibits good oxidation resistance up to 600 °C.

OUTOKUMPU MODA 409/4512

Outokumpu Moda 409/4512 is a weldable, titanium-stabilized 11.5% chromium ferritic stainless steel with good oxidation resistance in dry air. Because of its titanium alloying, Outokumpu Moda 409/4512 can be welded in all dimensions without becoming susceptible to intergranular corrosion. It is possible to use Outokumpu Moda 409/4512 at elevated temperatures, for example in automotive exhaust systems, where it is often used to replace aluminum-coated carbon steel. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: SS-1342. Producer or source: Outokumpu Oyj.

Effects of TiAl Alloy as a Binder on Cubic Boron Nitride Composites

Owing to their extreme hardness, cubic boron nitride (cBN) composites are widely used in cutting applications. The performance of cBN composites is closely related to the characteristics of the binder. Therefore, novel binders must be developed to improve the performance of cBN composites. In the present work, TiAl intermetallics were used as binders to fabricate cBN composites by employing a high-temperature and high-pressure sintering method. The phase transformation, sintering reaction mechanism, thermal stability, and mechanical properties of the resultant cBN composites were investigated. It was found that during the sintering process, Ti atoms preferentially reacted with boron nitride particles, whereas Al atoms enriched and transformed into TiAl3 phases and formed cBN/AlN, AlB2/TiN, and TiB2/TiAl3-layered structures eventually. The composites maintained good oxidation resistance at 1200 °C. A decrease in the particle size of the TiAl binder improved the uniformity of particle size distribution and increased the flexural strength of the composites.

NEONICKEL L605/25

NeoNickel L605/25 is a solid-solution strengthened cobalt-chromium-tungsten-nickel alloy that combines excellent high temperature strength with good oxidation resistance up to 980 °C (1800 °F). It is most commonly used in the aerospace industry due to its strength and durability in high temperature environments. It is also used for the manufacture of surgical implants. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Co-141. Producer or source: NeoNickel.

Synthesis and Properties of MoAlB Composites Reinforced with SiC Particles

To develop MoAlB advanced ceramic with improved mechanical properties and oxidation resistance, the use of SiC particles to reinforce MoAlB composites has been adopted. 5–15 vol.% SiC/MoAlB have been prepared and characterized. A flexural strength of 380 MPa and a Vickers hardness of 12.7 GPa were achieved in the 5 vol. %SiC/MoAlB composite, increased by 24% and 51%, respectively, as compared with those for MoAlB. Oxidation at 1200°C and 1300°C for 10 h in air showed that the 5 vol. %SiC/MoAlB composite has good oxidation resistance than MoAlB due to the formation of a dense and continuous scale composed of Al2O3 and SiO2, which prevents oxygen inward diffusion and the evaporation of oxides. We expect that the general strategy of second phase reinforcing for materials will help to widen the applications of MoAlB.

Oxidation Behavior of Quaternary Co-20Re-25Cr-3Si Alloy at Laboratory Air

The iso-thermal oxidation of the quaternary Co-20Re-25Cr-3Si alloy at 1,000–1,200 C under laboratory air for 24 h has been studied. The oxidation kinetics at 1,000–1,200 C follow parabolic law perfectly and the value of oxidation activation energy is 220.74 kJ/mol. Unlike the experimental condition of 0.1 MPa pure oxygen, under laboratory air Co-20Re-25Cr-3Si alloy presents a good oxidation resistance due to the formation of a dense and continuous layer of Cr2O3 in contact with the alloy. A 79% drop in oxygen pressure has changed the oxidation mode from catastrophic oxidation to mild oxidation. The thickness of the protective Cr2O3 layer decreases when temperature increases. Therefore, Co-20Re-25Cr-3Si alloy shows the best oxidation resistance at 1,000 C. Moreover, from another perspective, compared with Co-17Re-23Cr-3Si alloy, the addition of about 2% Cr can also improve the oxidation resistance of the alloy greatly by forming the protective Cr2O3 layer.

Effect of Al2O3 and SiO2 Inert-Fillers on the Microstructural Evolution and High Temperature Oxidation Resistance of B Modified Silicides Coatings Prepared by Pack Cementation Technology

In this study, B modified silicide coatings were prepared on Nb-Si based alloy with Al2O3 or SiO2 inert-filler by pack cementation technology. Both coatings primarily consisted of a (Nb,X)Si2 with a (Nb,X)B2 + (Nb,X)Si2 outer layer. After oxidation at 1250 °C for 100 h, the coatings showed good oxidation resistance due to the formation of a dense silica. The oxidation products of the coating prepared with Al2O3 inert-filler consisted of SiO2, TiO2 and Cr2O3, while that of the coating prepared with SiO2 inert-filler consisted of SiO2, TiO2, Cr2O3, and HfO2. The different oxidation products may be due to the different oxidation process of these two sample at initial oxidation stage.

Influence of a Discontinuous Process Strategy on Microstructure and Microhardness in Drilling Inconel 718

Nickel-base alloys are proven materials in the fields of the aerospace and oil industry, which is due to their characteristic material properties of high temperature strength, high toughness and good oxidation resistance. These properties are beneficial to applications in technical components in general. However, they also represent challenges for machining. Especially while drilling Inconel 718, high temperatures occur in the chip-formation zone that implicate high thermal load in the material and thus, influence the surface integrity, for example, by causing white layers. Hence, the development of strategies to improve the ability to supply cutting edges with cooling lubricant is becoming increasingly important. In this context, an alternative process design, the discontinuous drilling, takes place, characterized by a periodic interruption of feed motion and thus, chip formation. A minor retraction movement from the contact zone enables the cooling lubricant to reach the cutting edges and to reduce their thermal load. In comparison to the conventional process of drilling Inconel 718, the effects of discontinuous drilling with varying numbers of interruptions on the resulting surface integrity and further parameters of drilling qualities are analyzed. Thereby, the prevention of process-related phase transformations due to thermal impact was discovered when a discontinuous drilling strategy was implemented.

Automotive Steel with a High Product of Strength and Elongation Used for Cold and Hot Forming Simultaneously

A low-cost and easy-to-produce C–Mn–Cr automotive steel for both cold and hot forming is presented in this paper. The alloying element Cr was used to replace Mn in medium-Mn steel and instead of B in hot-formed steel, in order to achieve microstructure control and hardenability improvement, replacing the residual austenite-enhanced plasticization with multidimensional enhanced plasticization through multiphase microstructure design, grain refinement, and dispersion enhancement of second-phase particles. The products of strength and elongation for the cold-formed and hot-formed steel were 20 GPa·% and 18 GPa·%, respectively, while the tensile strengths were more than 1000 MPa and 1500 MPa, respectively. This new automotive steel was also characterized by good oxidation resistance. The mechanisms of strength and plasticization of the experimental automotive steel were analyzed.

Microstructure Factor of Creep Behavior in Near-α Ti Alloy

Heat-resistant Ti-Al-Nb-Zr alloys, which don’t contain Sn, have been designed to obtain good oxidation resistance above 600 °C. In addition, to design Ti alloys with best balance of creep and fatigue properties, prior β grain size which affects fatigue properties and lamellar microstructure which affects creep properties were controlled by heat treatment. In the present study, the effect of microstructure on creep properties of one of the alloys, i.e., Ti-7.5Al-4Nb-4Zr alloy, with the bimodal (B), the lamellar structures in small prior β grains (LS), and the lamellar in large prior β grains (LL) were investigated at 600 °C. The creep deformation mechanism for each microstructure was a power-law creep. However, the creep life varied depending on the microstructures. The longest creep life was obtained in LS with prior β grain size of 90 μm and interlamellar spacing of approximately 10 μm, while the shortest creep life was obtained in LL with prior β grain size of 550 μm and fine interlamellar spacing of less than 2~3 μm. This suggests that creep life is more affected by interlamellar spacing than by prior β grain size.