Compound purification of nickel base superalloy cutting waste through special cleaning agent attached to ultrasonic stirring

Abstract

The GH4169 nickel-based superalloy is a type of alloy that exhibits excellent properties. It has high creep strength, fracture strength, as well as good corrosion resistance, fatigue resistance, and oxidation resistance under high-temperature conditions, allowing it to be widely used in the aerospace, nuclear reactor, and oil industries. However, it is challenging to process superalloys because of their high hardness and considerable processing wastes, such as cutting fluid. Many processing wastes cannot be directly used for remelting due to issues like surface stains. However, the production of GH4169 superalloys requires low carbon content for recycling, so the alloy scraps that meet the standard after pre-cleaning can be obtained. This study explores the ultrasonic cleaning effect of superalloy scraps with different liquid-solid ratios, cleaning times, and cleaning temperatures to obtain the optimal cleaning conditions of GH4169 superalloy scraps. The content of carbon in unwashed superalloy scraps is as high as 0.2%, far exceeding the carbon content of the alloy itself (0.015–0.036%). After ultrasonic cleaning at 60 °C for 30 min with a cleaning solution having a solid-liquid ratio of 1:2.5, the carbon content of the scraps decreased from over 0.2%–0.048%, and the decarburization rate reached above 77%. After remelting the cleaned scraps into alloy bars, the composition content and properties of the bars meet the production requirements. The cleaning mechanism is analyzed, and the cavitation effect, saponification, and emulsification mode in the ultrasonic cleaning process are explained. This paper positively promotes recycling GH4169 nickel-based superalloy waste to protect environmental resources.