Ti-6Al-4V titanium alloy weldments were prepared by the conventional TIG and fast frequency double pulse TIG (FFDP TIG) waveforms. Arc shape, microstructure and mechanical properties of weldments were investigated. The arc core area of the FFDP TIG shrink gradually, the weldment fusion zone (FZ) width and heat affected zone (HAZ) width reduced by 18.2% and 31.3%. The molten pool intensive stirring effect and the heat input reduction by FFDP TIG waveform, resulting in the prior β grain size decreased by 55.6% and refinement of martensite αʹ structures. Microhardness, tensile strength of FFDP TIG weldment were higher than that of conventional TIG, the tensile strength and elongation reached 98.4% and 65.6% of the base metal, respectively. The results show that FFDP-TIG process improve the Ti-6Al-4V weldment microstructure and mechanical properties and can exhibit excellent performance in the practical applications.

Tungsten inert gas (TIG) is currently one of the most widely applied welding technologies. However, the arc energy divergence and high heat input of conventional TIG can lead to welding defects in heat-input-sensitive alloys (such as Inconel 718). Introducing a fast-frequency pulsed current (≥20 kHz) in TIG creates a welding process named fast-frequency pulsed tungsten inert gas (FFP-TIG). The arc behavior of FFP-TIG has advantages over conventional TIG in terms of arc contraction, arc pressure, and energy density. With an increase in the FFP current amplitude or frequency, the arc diameter and arc area are reduced, the arc pressure at the center of the arc is increased, and the arc energy divergence and arc temperature are reduced. The FFP-TIG weld method was adapted for Inconel 718 based on FFP-TIG arc behavior. This study provides fresh insight into the development and application of FFP-TIG arc physics research and industrial applications.

The Silicon Carbide (SiC) MOSFET inverter welding power supply produces high rates of voltage and current change (dv/dt and di/dt) as well as a reverse recovery current transient rate during the high-frequency and high-voltage switching process. This causes a serious crosstalk issue and affects the driving reliability of SiC MOSFETs. This research creates a half-bridge crosstalk model based on the properties of SiC MOSFET power devices and an inverter welding power supply. Further analysis is done on the crosstalk mechanism of the SiC MOSFETs used in the half-bridge application as well as the impact of the driving parameters on the switching process. A SiC MOSFET drive circuit with protection functions is designed. By constructing a double pulse circuit, the SiC MOSFET driving circuit’s functionality and its driving parameters are assessed. The driving waveform of the SiC MOSFET is stable and within the expected range in the SiC MOSFET inverter welding power supply. The experimental findings demonstrate the viability of the driving circuit that was created. SiC MOSFETs can operate consistently and produce an excellent switching waveform.