To allow this type of monitoring, a credible, properly calibrated measurement method is needed. It is especially desirable to use on-line/in-line monitoring methods to reduce/avoid post production quality checks that can result in revealing of systematic weld failures in large production batches. To perform the welding process correctly, it is necessary to know exact values of temperature.Īs Inconel 625 material is a rather expensive one and is often applied in critical applications, it is necessary to ensure the high quality of any made joints. Furthermore, there is a ductility dip temperature range (DTR) between solidus temperature (T S) and 0.5T S.
It is one for the critical factors of high hot cracks. Consequently, solidification cracking and liquation cracking occur due to the solid–liquid interface separation in the brittle temperature range (BTR), which is lower than the melting point of nickel-based alloys. The presence of intergranular liquid films results in microfissures because the liquid films cannot withstand the thermal and mechanical tensile stresses generated in the gas tungsten arc welding (GTAW) process. In the welding of nickel-based alloys, alloy elements segregate mainly at grain boundaries and form low melting point phases such as eutectic γ–γ′, Laves phase, and MC carbides along solidified grain boundaries. The solidus temperature of Inconel 625 is 1290 ☌ and the liquidus temperature is 1350 ☌. Additionally, strengthening of this material may be derived by precipitation of carbides or intermetallic phases. Inconel 625 is a solid solution-reinforced superalloy. Used in chemical processing, aerospace and marine engineering, pollution control equipment, and nuclear reactors. This alloy resists a wide range of severely corrosive environments and is especially resistant to pitting and crevice corrosion. Inconel 625 (EN 2.4856-NiCr22Mo9Nb) being a trademark of the Special Metals Corporation group is a nickel-chromium-molybdenum alloy with an addition of niobium that acts with the molybdenum to stiffen the alloy matrix and thereby provide high strength without strengthening heat treatment. They are used in the most thermally loaded parts of jet engines, accounting for nearly 50% of their mass. They are characterized by high corrosion resistance and high durability at temperatures up to approximately 1000 ☌. Inconel nickel-chromium superalloys contain approximately 15 to 20% chromium and iron additives up to approximately 18%, molybdenum up to approximately 16%, niobium up to approximately 5% and other elements (Co, Cu, W). It was found that by using the k-means clustering method it is possible to distinguish between correct and faulty (in terms of too low mechanical properties) joints. Precise temperature values allowed us to cluster welded joints in 3D feature space (temperature, hardness, linear energy). The best-reflected temperature correction map was selected and applied to obtain a temperature representation that differs from the FEM baseline by less than 10 ☌. It allows to precisely model heat source properties. The FEM simulations were calibrated according to the geometry of the fusion zone. The elaborated approach is based on comparison between infrared observation of the solidifying weld and precisely performed finite element method (FEM) simulation. The proposed method is used to reduce the influence of the reflected temperature of the hot torch and the arc on the temperature distribution observed on the surface of the welded joint using an infrared camera. In the paper, a temperature measurement credibility increase method is described and evaluated. Arc welding generates a high amount of heat that is reflected by the metallic surface of the welded object. Assessing the temperature of the joint in on-line mode is a vital task that is demanded to characterize the formations of terns formations that are taking place in a joint and result in reaching necessary properties of the joint.