η Phase Formation Mechanism at Cemented Carbide YG30/Steel 1045 Joints during Tungsten-Inert-Gas Arc Welding

Abstract

Cemented carbide YG30 and steel 1045 were welded with various Ni-Fe-C filling alloys via the Cemented carbide YG30 and steel 1045 were welded with various Ni-Fe-C filling alloys via the tungsten-inert-gas (TIG) arc welding. η phase formation at the welding joints was investigated via scanning electronic microscope (SEM), transmission electronic microscope (TEM) coupled with selected diffraction, and electron probe microanalysis methods. η phases in three different morphologies were identified and they appeared to form in different mechanisms. The η phase formed at the heat-affected zone (HAZ) exhibited a similar size to that of WC particles and its formation was mainly attributed to the inter diffusion among W, C and Fe, Co, Ni in solid-state γ phase. The large-size η phase near the interface between YG30 and weld bead was due to the coarsening of tiny η grains in the liquid weld bead. The small-size η phase was formed via precipitation from the γ phase during cooling. The η phase formation could be controlled by optimization of C and/or Ni concentration in the filling alloys.

A review: Suppression of the solidification cracks in the laser welding process by controlling the grain structure and chemical compositions

“…The carbon in the hard metal tends to diffuse into the steel during the welding process, which causes a reduction in the carbon content of the hard metal. Considering the Phase diagram of WC -Co and WC-Fe alloys, the appearance of η phases seems inevitable due to the narrow zone of the (WC+γ) phase (Zhao et al, 2011).…”

“…However, it can also distribute the new IMCs in the weld seam (Yu et al, 2016). For instance, Zhao et al (2011) Mai et al (Dimatteo et al, 2022) reported that controlling the melting ratio of metals is crucial in butt welding of Cu-Al. They used a 350 W pulsed Nd: YAG laser to investigate laser welding without the use of filler materials.…”

Dissimilar Welding and Joining of Cemented Carbides

“…TIG welding is a process used to join metals by heating them with an arc between a tungsten electrode and the metals [78]. On the basis of previous investigations [79,80], Zhao et al [81] and her group [82][83][84] patented novel Ni-Fe-C filler metals. TIG welding was observed to have the bridge ability to increase the metallurgical bonding.…”

Effect of Brazing Filler Metals and Welding Parameters on Laser Welding-Brazing Joints of WC-Co to S1045

“…Investigation on weldability of cemented carbide and steels has been carried out since the application of cemented carbide and tool and method of making the same [16,17]. Initial studies focused on the low wettability due to large mechanical properties between cemented carbide and steels, residual stress after weld thermal cycle, and metal dissolution in the bonding phases [18][19][20][21][22][23], which was the main mechanism causing the poor wettability [24].…”