Search

A novel electromagnetic ultrasonic-assisted spreading with molten Sn−9Zn solder on the surface of SiC ceramics was developed. The distribution and strength of the magnetic induction of an alternating magnetic field, the strength of the static magnetic field, and a numerical simulation of molten solder spreading behavior were investigated. The strength of the alternating magnetic field that was induced around the coil was proportional to the peak current, and the alternating current was induced in the periphery to change the direction periodically. The surface of the solder collapsed and spread under the action of electromagnetic ultrasound, accompanied by a vibration phenomenon on the solder surface, and subsequently, part of the solder below the coil broke and splashed, and the solder at the center constricted. The maximum spreading radius depends on the peak current and reached 12.4–14.1 mm. The direction of the Lorentz force pointed to the external solder overall, and gradually pointed to the surface of the substrate at the edge of the solder. The repulsion between the coil and solder biased the direction of the Lorentz force inside the solder. The horizontal Lorentz force of the solder below the coil reached 21.32–213.07 kN/m3, and the vertical Lorentz force was within 10.4–103.9 kN/m3at different peak currents. This new welding method can be brazed without direct contact with the substrate or solder, which prevents substrate cracking by ultrasonic vibration and has the advantages of easy process control, and protection of the experimental material.

In this work, Ni–Al2O3thin nanocoatings (TNCs) containing γ-Al2O3nanoparticles were fabricated by ultrasonic-agitated electrodeposition (UAE). The influence of ultrasonic power on the microstructure, surface topography, phase structure, microhardness, and wear and corrosion performance was also discussed in detail. These results demonstrated that ultrasonic power had a considerable influence on the surface microstructures of the Ni–Al2O3TNCs. At an ultrasonic power of 300 W, the microstructure of the NA-3 TNC changed significantly; the surface was compact, fine, and smooth in the micro-area and contained the highest level of Al2O3(9.9 wt%). Diffraction peaks of the Ni grains in all Ni–Al2O3TNCs appeared at 44.65°, 52.20°, 76.85°, and 92.55° assigned to the (1 1 1), (2 0 0), (2 2 0), and (3 1 1) planes, respectively, and corresponded to a face-centered cubic structure. The microhardness values of the Ni–Al2O3TNCs initially increased before decreasing slightly as the ultrasonic power increased from 100 to 400 W. The NA-3 TNC had the highest microhardness (~ 916.2 Hv) among the Ni-Al2O3TNCs tested. Furthermore, the NA-3 TNC processed the lowest corrosion current density (0.034 µA/mm2) and the highest maximum corrosion resistance. The average wear rate for the NA-3 TNC was only 26.1 mg/min.

We used ultrasonic-assisted brazing to join Al-Si-coated Ti alloys and Al alloys with a Zn-Al-Si filler metal. At the interface between the Ti alloy and Al-0.1Si alloy coating, a block TiAl3phase formed. In contrast, for the Al-5Si alloy coating, the interfacial reaction layer of the joint consisted of a block Ti(Al,Si)3phase and needle-like Ti7Al5Si12phase. Finally, a granular Ti7Al5Si12phase was formed at the joint interface for the Al-12Si alloy coating. The tensile strength of the joints formed with the Al-0.1Si and Al-12Si alloy coatings was only 160 -185 MPa, and cracks propagated mainly through the reaction layer. The tensile strength of the joints formed with the Al-5Si alloy coating ranged from 210 to 215 MPa, and cracks appeared entirely within the coating, subsequently expanding along the coating and ultimately resulting in failure of the joint.

We used ultrasonic-assisted brazing to join Al-Si-coated Ti alloys and Al alloys with a Zn-Al-Si filler metal. At the interface between the Ti alloy and Al-0.1Si alloy coating, a block TiAl3phase formed. In contrast, for the Al-5Si alloy coating, the interfacial reaction layer of the joint consisted of a block Ti(Al,Si)3phase and needle-like Ti7Al5Si12phase. Finally, a granular Ti7Al5Si12phase was formed at the joint interface for the Al-12Si alloy coating. The tensile strength of the joints formed with the Al-0.1Si and Al-12Si alloy coatings was only 160 -185 MPa, and cracks propagated mainly through the reaction layer. The tensile strength of the joints formed with the Al-5Si alloy coating ranged from 210 to 215 MPa, and cracks appeared entirely within the coating, subsequently expanding along the coating and ultimately resulting in failure of the joint.

This study reports the synthesis of Ni-TiN composite nanocoatings on a Q235 steel matrix using the electrodeposition technique, and were then treated at different temperatures. The surface morphology, structure, hardness, and abrasion performances of composite nanocoatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and friction-abrasion testing machine. SEM images illustrated smooth/dense surface morphology for Ni-TiN composite nanocoatings treated at 250 °C. XRD patterns revealed Ni and TiN phase appearance within Ni-TiN composite nanocoatings. The broader and low-intensity XRD peaks were observed for the composite following heat treatment at 250 °C, indicating the smallest size of TiN particle and Ni grain. Furthermore, Ni-TiN composite nanocoatings exhibited the highest hardness of 821 Hv following heat treatment at 250 °C. The frictional coefficient, wear rate, and indentation depth for Ni-TiN composite nanocoatings were found to be lowest at 0.45, 0.58 mg/min, and 13.8 μm, respectively after heat treatment at 250 °C. Furthermore, the Ni-TiN composite nanocoatings had peak abrasion resistance across three composite nanocoatings following heat treatment at 250 °C.

In this work, we present the capillary filling behavior of Sn-9Zn molten solder on the surface of SiC ceramic with different initial contact angles with and without electromagnetic ultrasonic action. The results showed that the capillary filling behavior did not easily occur in the native state. Electromagnetic ultrasonic action could promote the capillary filling behavior of the Sn-9Zn solder on the surface of SiC ceramic. When the peak current was 10 A, the maximum value of the capillary filling length of the solder at a contact angle of 90° was 11.56 mm. When the peak current was 100 A, the solder on the left side of the gap broke. The surrounding air induced an alternating magnetic field whose direction changed periodically; with opposite directions of the magnetic field generated by the left and right coils. The direction of the Lorentz force on the left side of the solder was opposite to the right side, and the alternating magnetic field influenced the direction of the Lorentz force inside the solder, where the Lorentz force inside the solder was directly proportional to the peak current. The sound pressure inside the solder also changed to positive and negative pressure in one cycle, where the maximum value was 1.67 × 105Pa.

The current paper reports successful syntheses of Ni-TiN composite coatings via pulse current (PC) and magnetic PC (MPC) depositions. The microstructural, nanomechanical, wear properties and wear mechanism of the Ni-TiN composite coatings were investigated via scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), a nanoindenter (NI) and a high frequency reciprocating wear test instrument. The results showed that the Ni-TiN composite coating deposited at magnetic intensity of 0.3 T had numerous homogeneously dispersed TiN particles. The size of the Ni grains and the TiN particles in the coating were of nanometer size, with an average diameter of ∼65 nm and ∼25 nm, respectively. The maximum hardness and Young’s modulus values for the Ni-TiN composite coatings, deposited at magnetic intensity of 0.3 T, were 34.85 GPa and 165.2 GPa, respectively. The wear results showed that the weight loss of the Ni-TiN composite coating was approximately 47.4 mg at a magnetic density of 0.3 T. Furthermore, the coatings deposited at 0.3 T presented low friction coefficients, with an average value of about 0.43.

Ni-AlN thin films were successfully fabricated via direct-current (DC), pulse-current (PC), and ultrasonic-assisted pulse-current (UAPC) deposition. The microstructure, microhardness, and erosion characteristics of the Ni-AlN thin films were determined with the use of scanning probe microscopy (SPM), X-ray diffraction (XRD), Vickers hardness test, electrochemical station, and scanning electron microscopy (SEM). SPM results revealed that the Ni-AlN thin films synthesized by UAPC deposition have a compact and fine morphology with average grain diameters of the Ni and AlN particles of approximately 97.7 and 40.2 nm, respectively. Based on the XRD results, the Ni-AlN thin films consist of Ni and AlN phases. The Ni-AlN thin films prepared by DC, PC, and UAPC deposition at 4.5 A/dm2current density exhibited an optimum microhardness value of 904, 943, and 987 HV, respectively. Based on the erosion test results, the films prepared by UAPC deposition possesses the best corrosion resistance among the prepared thin films. The corrosion potentials of the DC-, PC-, and UAPC-deposited films were -0.552, -0.473, and -0.446 V vs. SCE, respectively.