Metal Oxide Nanoparticle-Based Coating as a Catalyzer for A-TIG Welding: Critical Raw Material Perspective

Abstract

Besides a wide application in corrosion protection, wear resistance increase, providing thermal properties and power conversion, oxide coatings have found an alternative application in welding technology as catalysts of the tungsten inert gas (TIG) welding process. In this paper, the novel approach of fabricating a coating containing nanoparticles based on nanosized SiO2 and TiO2 and their mixtures was applied to the austenitic stainless-steel base metal. It was found that coatings increased depths of penetration, enabling a consumable-free welding. Using this method, the use of several critical and near-critical raw materials (e.g., Si and Cr), as well as the relatively expensive Ni can be completely avoided. The most effective coating in terms of weld penetration consisted of a mixture of nanoparticles, rather than unary oxide coatings based on nanoparticles. A model for liquid weld metal flow is proposed based on the metallographic examination of recrystallized grains and microhardnesses measured near the weld metal, supporting the reversed Marangoni convection theory.

Suppressing the Use of Critical Raw Materials in Joining of AISI 304 Stainless Steel Using Activated Tungsten Inert Gas Welding

“…In contrast, austenitic grains near the fusion line just under the surface remained unchanged, since the melt reaching this area already transferred part of its heat. These results are similar to ones presented in [30,37], where SiO 2 and TiO 2 nanoparticles were used as a basis for the coating. In A-TIG welding, where full penetration is achieved, grain coarsening under the weld metal is not possible, since in case of full penetration, there is no base metal.…”

“…This was in good agreement with microstructures in these zones, with a decreased hardness closely in [30,37], where SiO2 and TiO2 nanoparticles were used as a basis for the coating. In A-TIG welding,…”

“…The distance between the indentations was 0.5 mm. Indentation loading was 0.981 N (100 140 gf) on Wilson Tukon 1102 (Uzwil, Switzerland) device.141142 Microhardness measurement scheme[30].…”

Influence of Metallic Oxide Nanoparticles on the Mechanical Properties of an A-TIG Welded 304L Austenitic Stainless Steel

“…Several studies have proven that nano-sized particles possess a high efficiency. This is because the high specific surface area of the nano-sized particles results in a faster thermal dissociation and decomposition during arc heating compared to that of the micron-sized particles [ 11 , 12 , 13 ]. The flux is applied on the surface by a brush or in the form of a spray prior to welding.…”

“…Instead of aiming at optimizing the flux to achieve the maximum penetration as in our previous study [ 12 ], in this study, the influence of nanoparticle-based fluxes on the mechanical properties of the weld was determined. The obtained mechanical properties were compared to the base metal and procedures for determining the weld quality, which may be the impeding factor of the wider acceptance of A-TIG technology in the industrial sector.…”