Influence of Graphite Morphology on Phase, Microstructure, and Properties of Hot Dipping and Diffusion Aluminizing Coating on Flake/Spheroidal Graphite Cast Iron

Abstract

The influence of graphite morphology on the phase, microstructure and properties of hot dipping and diffusion aluminizing (HDDA) coating on flake/spheroidal graphite cast iron (FC/FCD) was investigated. The microstructure and properties of the HDDA coatings on FC/FCD were determined by the graphite morphology. The outer and inner layers of the HDDA coating comprised the Fe2Al5 and FeAl phases, respectively. The outer layer of HDDA on FCD was dense and uniform; however, some pores of different sizes were found in the outer coating on FC, resulting in looser HDDA coating. Hence, the wear resistance of the HDDA coating on FC was worse than that of the coating on FCD. During oxidation, many continuous oxidation channels were formed from the coating surface to the matrix in the HDDA coating on FC, resulting in the oxidation of graphite in the HDDA coating and the matrix. However, only exposed spheroidal graphite was oxidized in the HDDA coating on FCD. Thus, the high-temperature oxidation resistance of the HDDA coating on FC was also worse than that of the coating on FCD.

Process and High-Temperature Oxidation Resistance of Pack-Aluminized Layers on Cast Iron

“…When Al atom enters the oxide film from the metal/oxide film section, it will leave a vacancy in the metal lattice, and the vacancy migrates inward to the metal/oxide film section in the opposite direction, and the vacancy diffuses to the appropriate position and precipitates to form needle-like holes. On the other hand, the difference of Fe and Al concentration between the high-temperature infiltration layer and the matrix finally leads to the formation of the needle [3]. The gamma region is strongly shrunk because of the infiltration of Al atoms.…”

“…Therefore, components such as engine parts, brake pads and heat exchangers with the requests of high temperature and excellent fatigue resistance are made of cast irons [1,2]. In recent years, the maximum combustion temperature increased with the raising of car speed, resulting in the use of coatings to protect spheroidal graphite cast iron [3].…”

Archives of Foundry Engineering

“…Surface coating is a costeffective and simple technique which acts as a protective layer when applied to the surface of the substrate [6]. Hot-dip aluminizing is less expensive and an effective coating process to protect steels from oxidation and corrosion [1,7,8,9,10]. When applying aluminium as a coating material on the surface of the steel, it can form a corrosion resistance layer [11,12].…”

Computer Methods for Constructing Parametric Statistically Equivalent Models of High-Strength Cast Iron Microstructure to Analyze It’s Elastic Characteristics

“…Серія: технічні науки Відомі декілька основних підходів аналізу макроструктури матеріалу. До першої групи [1][2][3][4][5][6] належать експериментальні чи прямі дослідження. Для них необхідно створити зразок шляхом попередньої обробки та провести експеримент із прикладанням механічного навантаження [4][5][6], температури [1][2] чи інших зовнішніх факторів.…”

“…До першої групи [1][2][3][4][5][6] належать експериментальні чи прямі дослідження. Для них необхідно створити зразок шляхом попередньої обробки та провести експеримент із прикладанням механічного навантаження [4][5][6], температури [1][2] чи інших зовнішніх факторів. За результатами експериментів аналізуються показники міцності, пружності, пластичності та робиться висновок, який вплив має відповідна мікроструктура на: розвиток тріщини [1], фазовий склад [2], твердість досліджуваного зразка [6].…”