High-Temperature Wettability Investigations on Laboratory-Developed CaO-CaF 2 -SiO 2 -Al 2 O 3 Flux System-Based Welding
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ORIGINAL PAPER
High-Temperature Wettability Investigations on Laboratory-Developed CaO-CaF2-SiO2 -Al2O3 Flux System-Based Welding Electrode Coatings for Power Plant Applications Sumit Mahajan 1
&
Jagdish Kumar 1 & Rahul Chhibber 1
Received: 3 October 2019 / Accepted: 25 December 2019 # Springer Nature B.V. 2020
Abstract This article is an attempt to examines high-temperature wettability properties of laboratory-developed electrode coatings for power plant applications. The properties include contact angle between the solid/liquid interfaces, spreading area, surface tension, and work of adhesion. Coatings were prepared using CaO-CaF2-SiO2 -Al2O3 basic flux system. The sessile drop method was used to estimate the contact angle at the liquid/solid interface while surface tension was calculated using Young’s and Boni’s equations based on the measured contact angle. The interaction effect of individual minerals and their binary mixtures (CaO.CaF2, CaO.SiO2, CaO.Al2O3, CaF2.SiO2, CaF2.Al2O3, and SiO2.Al2O3) on the wettability properties were studied using the regression analysis. Optimum flux compositions were estimated using Multi-response optimization. The contact angle decreases when basic oxides (CaO, CaF2) were added in a higher proportion than the acidic oxides. With the decrease in the contact angle spreading area increased and CaF2 comes out to be the significant constituent causes the increase in the spreading area. Binary mixtures CaO.CaF2, CaO.SiO2, and CaF2.SiO2 has an increasing effect on the work of adhesion. Keywords Coating compositions . Wettability . Contact angle . Regression analysis . Surface tension . Spreading area
1 Introduction New alloys are designed and developed to meet the requirement of the high-temperature operating conditions in the thermal power plants. Quality of weldments is a severe challenge in obtaining desired performance of high-temperature application alloys. Thoughtful consideration towards selecting welding consumables is an essential requirement to address weld structural integrity issues. Welds should possess similar/
* Sumit Mahajan [email protected] Jagdish Kumar [email protected] Rahul Chhibber [email protected] 1
Mechanical Engineering department, IIT, Jodhpur, Rajasthan 342037, India
better properties as that of parent materials [1–3]. Various functions were performed by welding fluxes when melted at a higher temperature. One of the critical functions is to protect weld pool from the environmental gases and impurities by providing a protecting shield. It helps to clean the weld pool by removing harmful species like sulphur and phosphorus. Electrode coating fluxes provides better arc stability, weld bead, and geometry. Basic oxides (CaO, CaF2) are network breakers while the acidic oxides are network formers (TiO2, SiO2, Al2O3) which affect and controls the different physicochemical and thermophysical properties of the welding slags [4–11]. It is essential to investigate the behaviour of welding fluxes and welding slags at high-temperature, as this be
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