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.
Highlights
The traditional form of oxide coatings has several purposes, mainly to protect the base material against corrosion [1,2,3] and wear [4,5,6], to obtain certain thermal properties [7,8], and to be used for power conversion [9,10]
Compared to the metal inert gas (MIG), which is used for welding a similar array of materials, tungsten inert gas (TIG) suffers from a lower productivity due to a lower welding speed and relatively low penetration, even in the case of currents when an excess of 300 A
The increased microhardnesses obtained in the weld metal were the result of the application of a consumable material in the form of a welding wire
Summary
The traditional form of oxide coatings has several purposes, mainly to protect the base material against corrosion [1,2,3] and wear [4,5,6], to obtain certain thermal properties [7,8], and to be used for power conversion [9,10]. One of the most widely used welding processes is gas tungsten arc welding (GTAW) or alternatively called tungsten inert gas (TIG). This process is well known for producing high-quality welds in different metals and alloys, most commonly for different types of stainless steels and non-ferrous alloys based on aluminum, copper, nickel, titanium, etc. Compared to the metal inert gas (MIG), which is used for welding a similar array of materials, TIG suffers from a lower productivity due to a lower welding speed and relatively low penetration, even in the case of currents when an excess of 300 A. The low productivity of TIG can be addressed by the introduction of a coating applied before welding over the surface to be welded to act as a catalytic agent of the welding process kinetics
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