Piercing mandrel strengthening by surfacing with nickel aluminide-based alloy

Abstract

Abstract. Electrode composite wire (CW) was used for argon-arc surfacing of a thermalresisting nickel aluminide-based alloy (Ni-Al-Cr-W-Mo-Ta system) on the butt-end surface of the non-water-cooled piercing mandrel. It was shown that multipassing surfacing forms a defect-free deposited metal based on the γ'-Ni 3 Al phase of various structural origins. Using high-temperature sclerometry and thermal fatigue testing methods, the metal deposited with CW containing ultrafine particle of 0.3-0.4 % wt. WC carbide features increased resistance to thermal and force effects at temperatures up to 1200 °С. IntroductionIt is known that in the temperature range of 1100-1200 °С, the most efficient alloys are heat-resistant γ'-Ni 3 Al phase-based alloys produced by casting with high-gradient directed crystallisation with a specified structure throughout the whole workpiece [1][2][3]. This approach is not always possible or efficient when it is necessary to strengthen the most stressed areas of the metallurgical tools (piercing mandrels, pressing tools). Their intensive wear is due to the metal deformation in temperature-force cycling up to 1200 °С. Such operation conditions are the most common for large non-water-cooled mandrels, piercing the workpieces of difficult-to-form heat-resistant and corrosion-resisting steels and alloys [4,5]. This increases the relevance of the technologically flexible processes of surfacing of such mandrels with γ'-Ni 3 Al-based materials, featuring high deformation resistance of the deposited metal at temperature up to 1200 ºС. One way to increase the strength properties of Ni 3 Al-based metal is microalloying with rare-earth (La, Y, Ce) metals (REM) [6,7]. This makes it possible to stabilise the structure with nanosized (up to 70 nm) endogenous phases due to their low solubility in γ'+γ solid solutions [7]. At the same time, due to their surface activity, REMs decrease the melt surface tension and influence the energy required for nucleation centers, which increases their amount [8]. Such a mechanism can also be employed with refractory thermally stable compounds when introducing them into the weld pool melt in the form of exogenous ultrafine particles [9], as well as with REMs with high surface energy.The objective of this paper is to increase the deposited metal wear resistance under the thermalforce action using CW containing ultrafine components, as well as to study their effect on the structure formation of nickel aluminide γ'-Ni 3 Al-based metal.

Diagnostics of Weld Alloys for Resistance to High-Temperature Gas-Abrasive Wear

“…Металлографический и рентгеноструктурный анализ наплавленного металла 10Х4Н76М3В3Ю11РЦ показали, что он состоит из твердых растворов на основе γ'-Ni 3 Al фаз [17], образовавшихся в ходе эвтектической реакции из первичных γ-дендритов и в ходе перитектической реакции с участием γ-твердого раствора. Выявлено, что размер структурных составляющих эвтектики не превышает 10-15 мкм, при этом в металле отсутствуют крупные частицы упрочняющих фаз.…”

Development of Technology and Equipment for Non-destructive Testing of Defects in Sewing Mandrels of a Three-roll Screw Mill 30-80

“…One of the most popular types of rolled products for quality control today is steel vessels of the responsible purpose of small internal volume. That is why for the hot production of semi-finished products, lines consisting of screw rolling mills with a sewing mandrel installed along the axis are increasingly used [3][4][5] .…”

“…The technology provides for significant heating temperatures of the initial bars-blanks to ensure the continuity of the process of screw rolling, stitching and final heat treatment of products. The high temperature of about 2/3 of the melting makes it possible to ensure the high plasticity of the deformed material [5,6] .…”