Ceramic Welding Research Articles

A new method for direct welding of alumina and zirconia ceramics by ultrashort pulse laser for high temperature application

The direct welding of alumina and zirconia ceramics by ultrashort pulse laser is presented for the first time. Compared to traditional dissimilar ceramic joining techniques such as brazing and diffusion welding, this method shows various advantages, including operation at room-temperature, higher welding efficiency, and negligible impact on base materials. The joint microstructure consists of a combination of Al2O3 and ZrO2 phases, without new phases detected. By adjusting the laser focal point position, the phase content within joint is effectively regulated, successfully preventing crack formation in alumina substrate. The influence of laser power and welding speed on joint morphology and mechanical property is fully investigated. The highest four-point bending strength of 365.5MPa and shear strength of 33.4MPa are achieved. After experiencing thermal cycling test at 1000°C, the joint strength and microstructure does not exhibit significant changes, demonstrating the excellent high-temperature durability of the sample.

Enhancement mechanism of shear properties for SiO2 ceramics by laser welding with Al2O3/SiO2 powder

The laser direct fusion welding of SiO2 ceramics was a global challenge in the manufacture of radome. The paper explored the laser direct fusion welding of SiO2 ceramics, investigated the influence of filling powder addition and welding material composition on the formation of weld. The findings revealed that the addition of welding material effectively addressed the issue of weld formation in laser direct fusion welding SiO2 ceramic. However, the abundance of internal bubbles within the weld emerged as a significant impediment to further enhancing weld strength. The addition of SiO2/Al2O3 mixed powder not only significantly reduced the quantity and size of internal bubbles within the weld but also generated the strengthening phase Al2SiO5, leading to a substantial increase in weld shear strength, reaching a maximum of 106 % of the base material. The research results provided a new solution for direct melting welding of ceramics.

Ultrashort pulse laser welding of alumina ceramic and titanium

The direct welding of alumina ceramic and titanium using ultrashort pulse laser was successfully achieved for the first time. Benefitting from the extremely high peak power of ultrashort pulse laser, ceramics can be melted at a very low laser power. The emerging welding method was conducted at room-temperature without the need for preheating. Within the joint, a combination of Ti and Al elements was observed. A newly formed TiO2 phase was identified at the Al2O3/welding seam interface. Under the optimal welding parameters (welding speed: 0.8mm/s, laser power: 19.52W), the joint achieved a maximum four-point bending strength of approximately 134.9MPa. This study proposed a new methodology for butt welding of ceramics and metals and shows a much higher efficiency than the commonly used ceramic-metal joining approaches such as brazing and diffusion bonding.

Direct welding of dissimilar ceramics YSZ/Sapphire via nanosecond laser pulses

The joining of YSZ and sapphire was achieved through the utilization of nanosecond laser pulses. The microstructure, mechanical properties and forming process of the YSZ/Sapphire joint were systematically studied. The joint consists of an amorphous region guided by the temperature gradient and a dendritic recrystallization region. The amorphous region is situated centrally within the joint, while the recrystallization region surrounds it in a distributed manner. The reason for this phenomenon lies in the fact that the welding process occurring in the central region of the joint, and the extreme cooling prevents Al3+, Zr4+ and O2- ions from forming regular crystal phases. During this study when the laser power is set at 9 W and the scanning speed is adjusted to 80 mm/s, optimal welding interface performance can be achieved, resulting in a maximum joint shear strength of 32 MPa. This study provides a new idea for rapid and efficient welding of advanced ceramic.

Laser welding of ZrO2 ceramics and 304 stainless steel with Cu/AgCuTi composite welding

In this paper, Cu/AgCuTi composite material was used as an interlayer to join 304 stainless steel with ZrO2 ceramic by + 2 mm laser offsetting and laser power of 384 W. By retaining the unmelted Cu interlayer as the diffusion barrier, the stress of the joint interface is reduced and there was no obvious crack in the whole joint. Only on the ceramic side, due to the temperature gradient, a small amount of small cold cracks were generated in the area with a thickness of 30 μm. The unmelted Cu interlayer can absorb the welding stress at the interface through plastic deformation and creep. The fracture position of the joint started from the AgCuTi-ZrO2 ceramic bond interface and extended to the ZrO2 ceramic surface with a maximum tensile strength of 83 MPa.

Effect of process parameters on surface formation in laser welding of Al2O3 ceramic

The attainment of formability in ceramic welding presents an imposing quandary within the realm of the manufacturing industry. In this article, the laser welding of Al2O3 ceramics was carried out to compare and analyze the influence of laser power, welding speed, laser duty cycle, and other process parameters on the macroscopic morphology of the weld, weld cracking rate, and welded joint properties. The results show that Al2O3 ceramic welds have a greater tendency to cracking and that the laser power should be matched to the appropriate welding speed. When heat input increases, the weld cracking rate decreases and then increases. Ceramic welded joints with a weld cracking rate of less than 30 % and a bending strength of more than 4 MPa can be obtained when the heat input range is 17–20.5 J/mm for continuous laser welding or 20.5–24 J/mm for pulsed laser welding. In addition, under high heat input conditions, pulsed laser welding reduces the tendency for weld cracking compared to continuous laser.

Effect of process parameters on crack characteristics in laser welding of Al2O3 ceramic

The crack of ceramic weld is a worldwide problem for brittle material, high energy laser beam is expected to solve this problem. In this paper, the crack of fiber laser welding of Al2O3 ceramics was studied. The weld crack rate was used to characterize the crack condition of weld, and the influences of laser power, welding speed and defocusing distance on crack characteristics were carried out. The results showed that Al2O3 ceramics weld has obvious crack tendency, and the cracks mainly appeared on the weld center line. When the crack appeared on the weld center line, there was crack-free on the base metal. When the defocusing distance increased from +3 mm to +20 mm, the number of cracks gradually decreased. When the defocusing distance was greater than +17 mm, cracks-free appeared on the weld and base metal. Abaqus software was used to simulate the relationship between crack and stress based on thermal elastoplastic theory. The high crack areas, few crack areas and free crack areas were divided according to the maximum principal stress value. No matter what welding conditions, as long as the maximum principal stress was less than 1576 MPa, there was crack-free on the weld and base metal.

OPTIMIZATION OF THE STRUCTURE OF CERAMIC FLUX GRANULES

Currently, ceramic welding flux is widely used for automatic welding, since it has a low cost in combination with the required properties. One of the important advantages of this flux is the ability to alloy the weld. However, there are some disadvantages such as the strength of the granules and the hygroscopicity of the ceramic flux. Low strength leads to rapid abrasion of granules and formation of dust, therefore, to an increase in packed density and poor separation of the slag crust. In the presented work, the authors have considered the structure of granules of ceramic flux used inautomatic arc welding. The identified disadvantages can cause a negative effect on the strength of the granules and increase the hygroscopicity of the flux. To improve the quality of the produced flux, its structure was optimized in order to reduce pores and improve the wettability of the charge materials. After studying the literature data, it was assumed that in order to achieve the goal, it is necessary to grind the initial dry mixture of charge materials and reduce the viscosity of the binder. The granules obtained under laboratory conditions are distinguished by a good spreading of liquid glass and the absence of pores

Fabrication and modeling of ultra-hard and high-strength B4C-based laminated ceramics by brazing joining

The improvement in the comprehensive performance in strength, toughness, and hardness is significant for advanced ceramics. In the study, we successfully fabricated laminated structural ceramics by joining ultra-hard diamond-B4C–SiC ceramics (CdBS) with high-strength TiB2–B4C ceramics (TBC) according to the brazing joining method. Brazing parameters had a significant effect on the morphology of the laminated ceramics. The optimized shear strength of the welded interface could reach 109.42 ± 2.21 MPa with a brazing layer thickness of 150 μm under the brazing conditions of 930 °C and 10 min. The results of finite element analysis suggested that the maximum residual stress at the ceramic welding interface was 229.1 MPa. The compressive stresses were distributed on the ultra-hard CdBS ceramics side, thus enhancing the impact-resistant performance of the lightweight materials.

OPTIMIZATION OF THE STRUCTURE OF CERAMIC FLUX GRANULES

Currently, ceramic welding flux is widely used for automatic welding, since it has a low cost in combination with the required properties. One of the important advantages of this flux is the ability to alloy the weld. However, there are some disadvantages such as the strength of the granules and the hygroscopicity of the ceramic flux. Low strength leads to rapid abrasion of granules and formation of dust, therefore, to an increase in packed density and poor separation of the slag crust. In the presented work, the authors have considered the structure of granules of ceramic flux used inautomatic arc welding. The identified disadvantages can cause a negative effect on the strength of the granules and increase the hygroscopicity of the flux. To improve the quality of the produced flux, its structure was optimized in order to reduce pores and improve the wettability of the charge materials. After studying the literature data, it was assumed that in order to achieve the goal, it is necessary to grind the initial dry mixture of charge materials and reduce the viscosity of the binder. The granules obtained under laboratory conditions are distinguished by a good spreading of liquid glass and the absence of pores. KEYWORDS

Direct laser melting of Al2O3 ceramic paste for application in ceramic additive manufacturing

We develop the direct laser melting of ceramic paste technology for application in ceramic additive manufacturing (AM). The Al2O3 ceramic paste, which is a homogeneous mixture of DI-water and Al2O3 ceramic powders, was deposited on an Al2O3 substrate using free-forming extrusion (FFE), and subsequently melted by a CO2 laser. To better control the laser melting process, the flow behavior of the laser-melted Al2O3 was investigated by evaluating the microstructure of the laser-melted Al2O3 single tracks. When the laser scanning speed increased from 1 to 3.5 mm/s at a fixed laser power, the permeation of the molten Al2O3 into the surrounding porous paste was reduced, resulting in the improvement of the surface uniformity of the laser-melted Al2O3 tracks. Through optimizing the laser scanning strategy, a fully-dense Al2O3 layer with smooth surface was achieved. The phase composition and density of the laser-melted Al2O3 layers were evaluated to study their properties. The thickness of the dense Al2O3 layer varied from ∼90 μm to ∼120 μm periodically due to the line-by-line scanning of the Gaussian laser beam. In addition, the relationship between the melting thickness and the laser scanning speed was also investigated to further improve the controllability of the laser melting process. This direct laser melting of ceramic paste technology is promising for applications in ceramic AM, such as 3D printing of ceramic components and high-temperature ceramic welding.

Measurements of Density of Liquid Oxides with an Aero-Acoustic Levitator.

Densities of liquid oxide melts with melting temperatures above 2000 °C are required to establish mixing models in the liquid state for thermodynamic modeling and advanced additive manufacturing and laser welding of ceramics. Accurate measurements of molten rare earth oxide density were recently reported from experiments with an electrostatic levitator on board the International Space Station. In this work, we present an approach to terrestrial measurements of density and thermal expansion of liquid oxides from high-speed videography using an aero-acoustic levitator with laser heating and machine vision algorithms. The following density values for liquid oxides at melting temperature were obtained: Y2O3 4.6 ± 0.15; Yb2O3 8.4 ± 0.2; Zr0.9Y0.1O1.95 4.7 ± 0.2; Zr0.95Y0.05O1.975 4.9 ± 0.2; HfO2 8.2 ± 0.3 g/cm3. The accuracy of density and thermal expansion measurements can be improved by employing backlight illumination, spectropyrometry and a multi-emitter acoustic levitator.

Communications: PhotonicsViews 5/2019

PhotonicsViewsVolume 16, Issue 5 p. 12-17 CommunicationsFree Access Communications: PhotonicsViews 5/2019 First published: 09 October 2019 https://doi.org/10.1002/phvs.201970504AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Reference: E. H. Penilla et al.: Ultrafast Laser Welding of Ceramics, Science 365, 803 (2019); Volume16, Issue5October/November 2019Pages 12-17 ReferencesRelatedInformation

Ultrafast laser welding of ceramics

Welding of ceramics is a key missing component in modern manufacturing. Current methods cannot join ceramics in proximity to temperature-sensitive materials like polymers and electronic components. We introduce an ultrafast pulsed laser welding approach that relies on focusing light on interfaces to ensure an optical interaction volume in ceramics to stimulate nonlinear absorption processes, causing localized melting rather than ablation. The key is the interplay between linear and nonlinear optical properties and laser energy-material coupling. The welded ceramic assemblies hold high vacuum and have shear strengths comparable to metal-to-ceramic diffusion bonds. Laser welding can make ceramics integral components in devices for harsh environments as well as in optoelectronic and/or electronic packages needing visible-radio frequency transparency.

Investigation of bonding mechanism in friction stir spot welding of metal and ceramics

Investigation of bonding mechanism in friction stir spot welding of metal and ceramics

In Situ Atomic-Scale Oscillation Sublimation of Magnesium under CO2 Conditions.

Understanding the interactive role between Mg and CO2 is crucial for many technological applications, including CO2 storage, melting protection, corrosion resistance, and ceramic welding. Here we report observations of rapid oscillation sublimation of Mg at room temperature in the presence of both CO2 gas and electron irradiation using environmental transmission electron microscopy. The sublimation is mainly related to phase transformation of amorphous MgCO3. Differing from the direct formation of gas-state MgCO3, which attributes to the sublimation of pure Mg under a mild electron beam dose, a unique oscillation process is detected during the process of Mg sublimation under a harsh electron beam dose. The main reason stems from the first-order reaction of a reversible decomposition-formation of amorphous MgCO3. These atomic-level results provide some interesting insights into the interactive role between Mg and CO2 under electron beam irradiation.

Brazing Oxide Ceramics via the Ductile Interlayers of Niobium and Noble Metals

Optimized processes for obtaining the braze-welded joints of oxide ceramics based on Al2O3 and ZrO2 by pressure welding of ceramics with ceramics and ceramics with metals are developed. It is established that these braze-welded joints are prepared in the 1300–1600°C temperature range with pressure holding for 30–120 min under 15–25 MPa. The samples of welded pilot products that can be operated in both neutral and protective environment (up to 1500–1800°C) are produced according to the processes developed.

Simulation of friction welding of alumina and steel with aluminum interlayer

Friction welding is a complicated metallurgical process that is accompanied by frictional heat generation and plastic deformation. Since the thermal cycle of friction welding is very short, simulation becomes very significant. In the present work, a finite element-based numerical model has been developed to understand the thermo-mechanical phenomenon involved in the process of friction welding. The developed model is capable of predicting thermal distribution during friction welding of ceramics with metal using an aluminum interlayer for various time increments. Frictional heating at the interfacial region consumes the aluminum interlayer and establishes a bond between alumina and mild steel. Though there is mechanical mixing, the bond is incomplete in the aluminum-alumina interface. Due to the variation of thermal properties between alumina and mild steel, more amount of thermal stress is induced at the joint interface. Numerical simulation predicts the formation of residual stress in the alumina-mild steel side of the interface. This leads to incomplete interlocking that results in poor joint strength.

Structural study of sodium silicate glasses and melts

We report an X-ray diffraction study and modeling of the structure of sodium silicate glasses and melts that are used as binders in the production of the latest generation of ceramic welding fluxes. Experimental data and reverse Monte Carlo (RMC) simulations results are analyzed in comparison with results for a sodium silicate monolith and the water glass prepared from it. The RMC results agree well with structure factor and radial distribution function analysis data. The sodium silicate glasses and melts are shown to have a number of structural features, which have much in common with their crystalline counterparts. The high capacity of the silicate glasses and melts for water is due to the presence of nanopores formed (largely) by six-membered rings of silicon-oxygen tetrahedra and partially by sodium-oxygen octahedra.

Extending coke-oven life at Evraz Koks Siberia

The defects of the refractory lining at the coke batteries of Evraz Koks Siberia are considered, along with appropriate repair methods. Repair by ceramic welding is effective, but the assistance of Fosbel specialists is required.