Joining of Engineering Ceramics - Report Example

Joining of Engineering Ceramics By: Professor: Class: University: City: State: Date of submission: Joining of Engineering Ceramics Introduction Ceramics are the incredibly diversified family of the materials with the members spanning from the traditional ceramics such as pottery and refractoriness to the modern engineering ceramics including alumina and silicon nitride within the electrical devices, aerospace components, and the cutting tools. Even though there have been extravagant claim favouring the advancement of the ceramic materials like the ceramic engine which have proven to be inaccurate, it is clear that ceramics have been able to establish as the major engineering materials. When the metals are used in conjunction with the other materials, they tend to add functionality to the components, which in turn improves the application performance after using the appropriate joint design and technology (Passerone & Muolo, 2004, 420). The successful application of the ceramics in several devices and structures require certain types of joining with the metals. Hence, the ceramic-metal joints are widely applicable in various applications including the vacuum tubes, high voltage feed through the transistor packages, rocket igniter’s body, and sapphire-metal windows. The purpose of the joining of the metals involves the automobile engine components including the silicon nitride, silicon carbide, and yettria-stabilized zirconia. Moreover, the ceramic rotor was joined to the metal shaft through the new method that compensates the problems within the shrink fitting and active brazing methods. While joining the ceramics, it is important to consider the design to ensure the strength and durability of the components such as obtaining the similar aerodynamic features such as those in the metal rotor (Sapanathan et al., 2016, 111). The application of the method depends on the improved mechanical and thermal features such as the strength, creep, oxidation, and resistance to fatigue. Joining of Ceramics and Metals In the recent year, there have been a significant increments in the potentiality and actual uses of certain ceramics for the structural applications, which majorly require the strength. Furthermore, joining technology is vital for the application of ceramics considering the physical and economic limitation of the production of the large and the complex-shaped components with only the ceramics. One of the most important aspects of the ceramic and metal joint is the increment in the reliability of the ceramics. For many years, the studies of joining ceramics to the metals mainly for applications associated with electrical and other engineering technologies. The results of studies have been development of various methods (Indacochea, Polar & McDeavitt, 2005, 9). The mechanical joining, which involves using the adhesives with organics and the cements, have been able to dominate the industry due to the ease and inexpensiveness that it presents. The simplest methods are bolting and clamping. Ceramics and joining technology are rapidly changing the engineering practices. The production of the products from the consistently high quality technical ceramics usually needs the process engineering with an aim of ensuring that the product meets the quality requirements. In various parts of the machinery and equipment within the production lines, different components are made from the technical ceramics and some, which have been able to prove high level of efficiency over the years. While forcing on the products made from the ceramic materials, it is important to focus on certain core properties. These features include purity of the materials and their chemical conditions in terms of the material used with the process of ceramic production; the geometric dimensional stability, electrical insulation within the measurement systems, resistance to abrasion while mixing and grinding and in granulation (Akashi, Nukui & Kiyono, 2009, 986). Moreover, it is critical to consider the dimensional stability in the high-temperature applications and the thermal and thermo-mechanical resistance. The properties are not only vital for the production of technical ceramics bur also for the material-to-material joining works in various technologies such as metallic brazing and glass soldering technology. Furthermore, the properties are also important in ensuring successful products of these products. In most cases, the engineers tend to adapt the mechanical and thermal features of the metal and ceramic partners to be joined to ensure the existence of sufficiently narrow geometrical dimensions tolerances. In such cases, the post matching of the joined component is unnecessary since it is costly. Raw Materials Preparation and Joining Processes During the early stages of the classical ceramic engineering process chain, there is mixing and grinding of the raw materials. The grinding and mixing processes with an objective of rendering the powder particles in a their sufficient, sinter-active form and achievement of the homogenous mix of various inorganic components in powder form. However, it is important to give due concern to the risks associated with contamination of the powder caused by the ingress of the foreign substances into the ground powder. Accordingly, at the initial ceramic process chain, there are key parameters that could influence the achievement of the required quality material. Normally, the process uses the grinding the media that present lower degree of purity compared to the material for grinding. Therefore, the grounded particles from the grinding media could impair the quality of the ceramic made from the ground materials. However, much consideration is important for the products made of the high-grade oxide and the non-oxide ceramic, which makes it important to use only the grinding and the mixing media with purity level that at least matches that of the material under grinding. Moreover, the process could employ abrasion resistance to ensure that that the ingress of the foreign material within the ground material is negligibly low. Granulation and Shaping The transformation of the milled ceramic material generated from the aqueous suspensions usually require the granulation and drying step for achievement of the material states which is consider suitable in shaping the through pressing. It is for such purpose that most engineers often use the spray dryers for the production of the press granule within the hydrothermal conditions, which makes it important to feed the suspension within the suitable pipeline system using the pump to the dryer and sprayed out using the spray lance into the interior that has been treated to several 1000C. As for the wear-resistant materials for ceramics, for many years, there have been uses of long-term resilient components made from the oxide and non-oxide ceramics due to their reliability. Depending on the composition of the ceramic suspensions, they normally contain high-purity and dense-sintered materials base on the Al2O3, doped ZrO2, or Si3N4 (Lewinsohn, Singh & Henager, 2012, 205). There are flowmeters installed within the pipeline systems of the spray dryer for the regulation and controlling processes and works in accordance with the magnetic induction principle with the tabular measurement of the cell made of the oxide ceramic that has high-vacuum tight integrated electrodes. The process of shaping the ceramic compounds in the injection moulding leads in the injection zones of the systems to the high stress of the abrasions that tends to commensurate various economic consequences. One of the ways of making such operations efficient is using the components that are made from the oxide and non-oxide ceramic materials. The properties of such materials include high level of wear resistance, resilience to torsion, absence of deformation, modulus level of elasticity, and unavailability of the contact corrosion, high edge stability, and high compressive strength. Moreover, properties also need to include realization of the force, components of ceramic-metal composite, and form-fit and substance-to-substance ceramic-ceramic. On the account of such properties, the components of the systems made from such features tend to achieve with no exception compared to the other conventional metallic components. Glass Soldering: Ceramic-ceramic and Ceramic-metal Normally, the metallic soldering that take place above 4500C are classified conventionally as brazing. Moreover, the composites of the ceramic-metal are brazed in the presence of silver-based brazing soldier including AgCu28 or AgCu26, 6Pd5 that occurs at temperatures between 800 and 850°C. Considering that the metallic materials are irresistible to the oxidation process, the process of brazing through the electrically heated furnaces operate in the presence of the inert gases like H2, N2, Ar, and in the vacuum area (Taylor, 2011, 145). For instance, within such furnaces, the components of the oxide ceramic meant for electrical feed or thermocouples for insulating the thermocouple elements mainly consisting of the W-Re alloys. The electrical insulating material made of the dense-sintered Al2O3 ceramic has been able to prove in many ways effective and it exhibits important features. Besides the application as the electrically insulating material, to certain extent, the fixtures holding various components to be joined within the geometrically exact positive relative to one another during the brazing process are made sometimes of the oxide ceramic materials such as Al2O3 or ZrO2. However, it is important to note that whenever the standard fixtures are made of the granite which have insufficient strength, the thermal expansion of the level of geometric tolerance values could realizable with such; hence, the recommendation of using the oxide-ceramic fixtures (Zhao et al., 2011, 393). Compared to the brazing technology, glass soldering method in joining the ceramic to ceramic is less complex in regards to the technical equipment needed as it could be performed generally in the air within an electrically heated chamber or the furnace considered of a simple design. Nonetheless, it is vital to note that in the soldering fixtures, only the materials of oxidation resistant majorly the Al2O3 ceramic in the porous or dense-sintered is usable. There is need for special attention in such cases especially for the risks of the product being soldered to the furnace with the glass soldier. Furthermore, the glass soldering technique used in joining ceramic to the metal usually needs a soldering furnace that operates with the inert gas atmosphere. Ceramic Materials The ceramic materials tend to exhibit the very strong covalent which is stronger than the metallic bond or ionic bond. Such property confers with properties commonly associated with ceramics such as high hardness, low thermal and electrical conductivity, chemical inertness, and high level of comprehensive strength. According to Zhou & Breyen (2013, 219), such high level of bonding also accounts various less attractive features of the ceramics including low tensile force and ductility. However, there are wide range of properties are not associated with ceramics. For insistence, the ceramics are perceived to be insulators of electricity and heat; the ceramic oxides are the basis for the high temperature superconductivity. The major compositional classes of the engineering ceramics are the oxides, carbides, and nitrides. Control in the microstructures allow for the production of the ceramic spring and ceramic composites. Table 1: Properties of Ceramics Joining of Ceramics There are several possible methods of joining the ceramics to themselves and to the others dissimilar materials. With such methods, while considering to join the ceramics, it is important to consider various factors including the cost, applied stress, materials to be joined, design of the component, operational temperature, the desired component function such as the strength, resistance to wear, and electrical insulation, and the desired level of joint hermeticity. In the 1980s, there was boom for engineering ceramics with the emergence of the materials such as the silicon nitride and SiAlONs, which shape things. For many years, the focus was into the new materials and the major goal was production of an all-ceramic car engines (Messler, 2004, 601). Nonetheless, such ceramic future never became a reality as it failed to match the required expectations leading to the development of more advanced joining methods. Currently, ceramics are important in conjunction with the other materials as they add to the functionality such hardwearing surfaces, increased resistivity in corrosion, high temperature protection, and ultra-hard materials used in cutting. According Krenkel(2008, 101), despite the obvious significance of joining the ceramics, it is neglected during the design step. Moreover, the engineers tend to join the ceramics into different components as if they were high performing metals which little thought to the conditions of the services or the joining operations. As a result, there could be two outcomes: part fails with designers concluding that the ceramic was unsuitable and metal used as before and the high cost of the design might be required if the ceramic is used. While joining the ceramics, there are factors to consider such as selection of the materials, the joining design, best practice, and ceramic technologies, which forms the basis of the methods. In the modern engineering, the ceramic technologies used range from the simple mechanical attachments including the compression fit used within the part plugs through the liquid phase process including the adhesive bonding and brazing (Suganuma, 2013, 778). In addition, there are considerations like the joining atmosphere and size of the components, time and cost constraints worth noting. Ultrasonic Joining Ultrasonic joining is a method majorly used within the plastic industry has been applied in the combination of the ceramic and metal such as zirconia/steel, glass ceramic/copper, alumina/stainless steel, and alumina/aluminium. The method is applicable in various areas including batteries, textile-cutting equipment, batteries, thread guides, and heavy-duty electrical fuses. Research by Singh, (2011, 232) revealed that the major advantage of the processes is that they are very fast joining times, surface preparation is not important unlike the other ceramic processes, and lacks the melting and intermetallic formation. Nonetheless, to join the metals considered hard like steel, there is need for soft and deformable interlayer. The limitation presented by the ultrasonic joining of the ceramics is that the films or the thin sheets of the metal could be joined to the ceramics. In the joining process, ultrasonic method requires the transducer assembly that operates about 20kHz which is the ultrasound source combined to the sonotrode. Normally, the sonotrode is the tip placed in contact with the work piece and heat generation is localized at the interface to ensure creation of temperatures of up to 6000C while utilizing the interlayer of aluminium. In a research undertaken by Gourley and Walker (2012, 150)revealed that in the ultrasonic method, the mechanism of bonding depends on the shear of vibration stress on the metal that exceeds the elastic limit combined with the breakdown of the surface oxide films that exposes the clean metal automatically. Moreover, the clamping force tends to exert the plastic deformation on the metal, which in turn increases the interfacial contact that occurs between the ceramic and metallic material. The mechanical keying finally occurs across the interface of the two then there is the formation of the joint perhaps with certain interactions of the chemicals. Figure 1: Illustration of the Ultrasonic Welding Transient Liquid Phase Bonding The transient liquid phase bonding is another joining technique with the ability of producing the bond at very low temperatures compared to that at would be used. Currently, there is adoption of technologies for various ceramics that use interlayer based on the glasses like the oxyntrides meant to join SiAlON or the pure metals and alloys including the Ge and Ge-Si meant to join the SiC and SiC/SiC composites (Rodriguez & Cooper, 2013, 65). The mixture of the silicon nitride, silica, yttria, and alumina are applicable through the spray coating to one of the joint surfaces. While heating the the samples to more than 16000C, the load of 2MNm-2 is applicable. Normally, there is formation of the joints at such temperatures within 10-80 minutes. When the temperatures reach 14000C, the oxide components tend to react and result in the formation of Y-Si-Al-O phase of the liquid, which contributes significantly, to sintering and densification. (Sandhu, Singh & Singh, 2015, 2342) The weakness of the method is that there is need for favourable reaction between the interlayer and the substrate. In the silicon nitride, there is need for redistribution of the interlayer and penetrate the microstructure which are adjoining. Figure 2: Joining methods for ceramic-ceramic and ceramic-mental joints General Problems in Ceramic Joint Ceramics are important in the modern engineering field; however, the major challenge is the achievement of high integrity joints between the ceramics and the metals. Besides, ceramics’ properties tend to attract many engineers though they pose major handicaps associated with joint fabrication. Considering the level of inert associated with ceramics, it is impossible to use the conventional methods of joining the metals (Pourmohammadi, 2013, 571). To acquire the desired quality of the bond, there is need for high temperatures and pressures and the media for bonding with the reactive element. Several problems occur between the ceramics and metallic materials like the configuration of the atom bond, physical, and chemical features. In ceramic materials, the ionic and covalent bonds are the major feature of the atomic bond configurations, which leads to high stability of the peripheral electrons. Therefore, the general fusion method, welding, in joining the ceramics is almost impossible with the molten metal generally failing to wet the surface of the ceramics (Sala, 2013, 425). While using the brazing method in joining certain ceramics to the metal, metallization of the ceramic surface is vital using the inactive brazing filter metal or the active brazing alloys to ensure production of a reliable joint. In addition, the ceramics have thermal expansion coefficient much lower than the metals (Loehman, 2010, 122). As a result, there is generation of stress within the ceramic/metal joint associated with the mismatch of the expansion, which in turn leads to degradation of the mechanical features within the joint that cause cracks after joining. According to Campbell (2011, 192), most of the ceramics also have low thermal conductivity and susceptibility from the thermal shock. Through the fusion welding method in the joining the ceramics by concentration of the heat, cracking of the ceramics usually occurs easily. Therefore, it is significant to ensure adequate reduction in the temperature gradient within and around the zone of fusion, careful control of the heat, and the speed of cooling while joining the metal and ceramics. Conclusion There are different methods used in joining the ceramics to the metals. The state-of-the-art methods are refractory metallization and active brazing of the metal from various perspectives: applications and processing. There have development of various methods of forming the ceramic/metal joints with an aim of combining the properties of different materials for both electrical and structural applications. However, it is important to note that the methods not only address the physical and chemical compatibility needs, but also ensure the existence of bond between dissimilar materials to ensure the survival in the rigour uses that result from the unavoidable mismatches like during the expansion, thermal cycling behaviour, elastic, and reactive. . In various parts of the machinery and equipment within the production lines, different components are made from the technical ceramics and some, which have been able to prove high level of efficiency over the years. Ceramics are important in the modern engineering field; however, the major challenge is the achievement of high integrity joints between the ceramics and the metals. Joining the ceramics to the metals is not easy with consideration of certain important factors that mainly emerge from the difference in the physical and chemical natures of the ceramics and metals to be joined. References Akashi, T., Nukui, T., & Kiyono, H. (2009). Liquid-phase oxidation joining of oxide ion conducting ceramics via Al/heat resistant alloy/Al multilayer interlayers. Journal of the Ceramic Society of Japan, 117(1369), 983-986. Campbell, F. C. (2011). Joining: Understanding the basics. Materials Park, OH: ASM International. Gourley, R., & Walker, C. (2012). Brazing and Soldering 2012, IBSC Proceedings of 5th Intl. Conference. Materials Park: A S M International. Indacochea, J., Polar, A., & McDeavitt, S. (2005). Challenges in Joining Advanced Ceramic Materials: Interface Formation of Ceramic/Metal High-Temperature Brazes. Materials Science Forum, 502, 7-12. Krenkel, W. (2008). Ceramic matrix composites: Fiber reinforced ceramics and their applications. Weinheim: Wiley-VCH. Lewinsohn, C., Singh, M., & Henager, C. (2012). Brazeless Approaches to Joining Silicon Carbide-Based Ceramics for High Temperature Applications. Advances in Joining of Ceramics, 5(2), 201-208. Loehman, R. E. (2010). Characterization of ceramics. New York: Momentum Press. Messler, R. W. (2004). Joining of Ceramics and Glasses. Joining of Materials and Structures, 2(3), 583-619. Passerone, A., & Muolo, M. (2004). Metal-ceramic interfaces: wetting and joining processes. International Journal of Materials and Product Technology, 20(6), 420. Pourmohammadi, A. (2013). Nonwoven materials and joining techniques. Joining Textiles, 5(3), 565-581. Rodriguez, J. A., & Cooper, H. J. (2013). Large ceramic femoral heads: what problems do they solve? The Bone & Joint Journal, 95(11), 63-66. Sala, G. (2013). Advanced metal–ceramic joining techniques for orthopaedic applications. Joining and Assembly of Medical Materials and Devices, 4(2), 407-448. Sandhu, K. S., Singh, G., & Singh, F. P. (2015). A Literature Review on Fusion Joining of Similar and Dissimilar Materials by Microwaves. International Journal for Scientific Research & Development, 3(5), 2321 - 2613. Sapanathan, T., Raoelison, R., Buiron, N., & Rachik, M. (2016). Magnetic Pulse Welding: An Innovative Joining Technology for Similar and Dissimilar Metal Pairs. Joining Technologies, 2(1), 105-122. Singh, M. (2011). Ceramic integration and joining technologies: From macro to nanoscale. Hoboken, NJ: Wiley-American Ceramic Society. Suganuma, K. (2013). Joining Ceramics and Metals. Handbook of Advanced Ceramics, 1(4), 775-788. Taylor, L. (2011). The ceramics bible: The complete guide to materials and techniques. San Francisco: Chronicle Books. Zhao, Y. N., Zhang, W. L., Hou, G. Q., & Liu, L. H. (2011). The Joining of Oxide Ceramics with Quartz Fiber by Interlayer. AMR, 337, 392-395. Zhou, Y., & Breyen, M. D. (2013). Joining and assembly of medical materials and devices. Cambridge: Woodhead Publishing Limited. Read More