NASA Contributions to Metals Joining

Survey of NASA supported metals joining research having industrial application

High Current Plasma Electrolytic Oxidation Coating Processes for Wear and Corrosion Prevention of Al 2024

Plasma electrolytic oxidation (PEO) treatments have been used in the aerospace and automotive industries because the coating formed on light metals or alloys has great hardness, high wear, corrosion, and oxidation resistance, and a low friction coefficient that improves lifetime length and provide a higher surface quality. However, the PEO treatments that are presently used for industrial applications require a long period of time to confirm the quality of the coating. For this reason, the present study seeks to increase the current density of PEO treatments to improve their efficiency and explore the performance of the obtained coatings. It was found that for high current density (0.18A/cm2) PEO treatments, smaller ratio, such as 50% and 70%, is beneficial to obtaining a better performance coating. When compared with the coating of a “normal” (current density: 0.09A/cm2) PEO treatment, it had better wear resistance; however, for corrosion resistance, it had a lower performance than the coatings obtained by the “normal” current density PEO treatment which was attributed to the negative influence of porosity increase

Plasma Electrolytic Oxidation (PEO) Coatings

Plasma electrolytic oxidation (PEO), also known as micro-arc oxidation (MAO), functionalizes surfaces, improving the mechanical, thermal, and corrosion performance of metallic substrates, along with other tailored properties (e.g., biocompatibility, catalysis, antibacterial response, self-lubrication, etc.). The extensive field of applications of this technique ranges from structural components, in particular, in the transport sector, to more advanced fields, such as bioengineering. The present Special Issue covers the latest advances in PEO‐coated light alloys for structural (Al, Mg) and biomedical applications (Ti, Mg), with 10 research papers and 1 review from leading research groups around the world

The effect of electrolytic solution composition on the structure, corrosion, and wear resistance of peo coatings on az31 magnesium alloy

Plasma electrolytic oxidation coatings were prepared in aluminate, phosphate, and silicate-based electrolytic solutions using a soft-sparking regime in a multi-frequency stepped process to compare the structure, corrosion, and wear characteristics of the obtained coatings on AZ31 magnesium alloy. The XRD results indicated that all coatings consist of MgO and MgF2, while specific products such as Mg2 SiO4, MgSiO3, Mg2 P2 O7, and MgAl2 O4 were also present in specimens based on the selected solution. Surface morphology of the obtained coatings was strongly affected by the electrolyte composition. Aluminate-containing coating showed volcano-like, nodular particles and craters distributed over the surface. Phosphate-containing coating presented a sintering-crater structure, with non-uniform distributions of micro-pores and micro-cracks. Silicate-containing coating exhibited a scaffold surface involving a network of numerous micro-pores and oxide granules. The aluminate-treated sample offered the highest corrosion resistance and the minimum wear rate (5 × 10−5 mm3 N−1 m−1), owing to its compact structure containing solely 1.75% relative porosity, which is the lowest value in comparison with other samples. The silicate-treated sample was degraded faster in long-term corrosion and wear tests due to its porous structure, and with more delay in the phosphate-containing coating due to its larger thickness (30 µm)

Surface Modification Of Metals By Cold Gas Dynamic Spraying Technique

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2012Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2012Alüminyum esaslı kaplamalar çeşitli endüstri kollarında metal yüzeylerinin korozyon direncini arttırmak amacıyla kullanılmaktadır. Ancak, bu kaplamalar metal yüzeylerinin korozyon direncini arttırmalarına rağmen zayıf mekanik özellerinden ötürü yüzeyi mekanik kuvvetlerden koruyamazlar. Alüminyum ve alaşımlarının zayıf mekanik özellikleri sert seramik takviye malzemesi ilavesi ile yüksek oranda geliştirilebilir. Bu noktada, sahip oldukları yüksek mukavemet/yoğunluk oranları, uygun mekanik özellikleri ve yüksek aşınma dirençleri nedeniyle alüminyum matrisli seramik partikül takviyeli kompozit kaplamalar korozyon ve mekanik özelliklerinin birlikte gelişmesini sağlarlar ve bu tarz kaplamalar ilgi odağı olmaktadır. Bu çalışmanın amacı T6-6061 Al altlık üzerine soğuk gaz dinamik püskürtme tekniği ile 7075 Al matrisli seramik partikül (B4C, SiC ve Al2O3) takviyeli kompozit kaplama gerçekleştirmektir. Bu çalışma kapsamında, besleme toz karışımlarının üretilmesi için seramik partiküller hacimce oranları %10, 20 ve 40 olacak şekilde 7075 Al tozları ile karıştırılmıştır. Besleme toz karışımları nozül giriş basıncı 0.98 MPa ve sıcaklığı 300°C olan helyum proses gazı kullanılarak püskürtülmüştür. Kaplamaların karakterizasyonu mikroskobik incelemeler, sertlik ve yapışma mukavemet ölçümleri ile aşınma ve elektrolitik korozyon testleri ile yapılmıştır.Al based coatings are used in various industrial applications to protect metals against corrosion by means of anodic protection due to formation of a very thin and impervious aluminum oxide layer. However, these coatings cannot protect the surface from the mechanical forces due to their poor mechanical properties. At this point, coatings of aluminum matrix ceramic particle reinforced composites have attracted much attention recently owing to high strength to weight ratios, suitable mechanical properties and higher wear resistance in comparison to conventional monolithic alloys without sacrificing the corrosion resistance of aluminum. The aim of this study is to produce 7075 Al matrix ceramic particle (B4C, SiC and Al2O3) reinforced composite coatings on T6 6061 Al substrate by cold gas dynamic spraying technique. Within scope of this study, ceramic particles were mixed with 7075 Al particles at volume ratios of ceramic particles of 10, 20 and 40 vol. % to produce feedstock powder mixtures. Feedstock powder mixtures were sprayed using He as a process gas with a nozzle inlet pressure of 0.98 MPa and a temperature of 300°C. Characterization of coatings were carried out by microscopic investigations, hardness and bond strength measurements as well as wear and electrolytic corrosion tests.DoktoraPh

The materials processing research base of the Materials Processing Center

The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis

Corrosion of cast aluminum alloys: a review

Research on corrosion resistance of cast aluminum alloys is reviewed in this article. The effect of the main microstructural features of cast aluminum alloys such as secondary dendrite arm spacing (SDAS), eutectic silicon morphology, grain size, macrosegregation, microsegregation, and intermetallic compounds is discussed. Moreover, the corrosion resistance of cast aluminum alloys obtained by modern manufacturing processes such as semi-solid and additive manufacturing are analyzed. Finally, the protective effects provided by different coatings on the aluminum cast alloys?such as anodized, plasma electrolytic oxidation (PEO), and laser?is reviewed. Some conclusions and future guidelines for future works are proposed