Aluminide Diffusion Coatings on IN 718 by Pack Cementation

Abstract

This paper addressed the issues of both direct and indirect synthesis of Ni aluminides by pack cementation (pure Ni and IN 718 superalloy). On the Al-Ni diffusion twosome under pressure, at temperatures below and above the Al melting temperature, the appearance and evolution of diffusion porosity because of the Kirkendall–Frenkel effect manifestation was highlighted. It has been confirmed that, as the temperature rises above the Al melting temperature, the porosity decreases. Nickel-based superalloys, and in particular IN 718, significantly increase their performance by increasing the aluminides proportion in the top diffusion coating. This is made possible by changing the value of the Al and Ni weight percentage ratio in this area (noted as Al/Ni). In the case of the diffusion twosome between IN 718 and pack aluminizing mixtures, having in their composition as active components Al powder, Ferroaluminum (FeAl40) or mixtures of Al and Fe powders, at processing temperatures above the Al melting temperature, by modifying the active component of the mixture, substantial changes in the Al/Ni values were observed, as well as in the maximum %Al in the diffusion coating and of its thickness. It was found that, when switching from Al to FeAl40 or powder mixture (Al + Fe), the Al/Ni value changes between 3.43 and 1.01, from initial subunit values. The experiments confirmed that the highest %Al in the top aluminized diffusion coating, for IN 718, was obtained if the powder mixture contained 66.34 wt.% Al.

Recent Advances in the Deposition of Aluminide Coatings on Nickel-Based Superalloys: A Synthetic Review (2019–2023)

“…Pack cementation is a process in which metal parts or components are placed in a container filled with a mixture of powdered metal and a chemical activator, typically argon or nitrogen [6]. The container is then sealed and heated to a high temperature, allowing the powdered metal to diffuse onto the surface of the parts, and consequently forming The main aim of this review is to introduce and summarize the recent achievements related to AC deposition by using conventional techniques, including pack cementation (PC), slurry aluminizing and chemical vapor deposition (CVD).…”

“…Pack cementation is a process in which metal parts or components are placed in a container filled with a mixture of powdered metal and a chemical activator, typically argon or nitrogen [6]. The container is then sealed and heated to a high temperature, allowing the powdered metal to diffuse onto the surface of the parts, and consequently forming a hard, wear-resistant coating (Figure 2).…”

“…It was reported that δ-Ni2Al3 and β- Although PC is commonly used as a conventional process in different industries, there are many new reports that provide new insights into such methodology. Cojocaru et al [6] used pack cementation to deposit an NiAl coating on Inconel 718. The formed NiAl layer was well adhered to the substrate material and was characterized by improved hardness of 40HRC due to the precipitation of the δ-Ni 3 Nb-hardening phase inside the grains of the solid solution γ. Gloria et al [7] presented optimized halide-activated pack cementation technology for the Mar-M246 alloy, the effectiveness of which was assessed through hightemperature oxidation tests in air up to 1000 • C. The coated nickel-based superalloy exhibited superior oxidation resistance as compared to its wrought state.…”

“…Although all of them were used to deposit NiAl coatings to improve some functional properties of the base materials, one can expose different approaches leading to the same findings. It could be noticed that PC methods are mainly used to deposit pure NiAl or β-NiAl coatings [6,7,[12][13][14][15][16][17]23,24]. Some reports analyze the addition of different oxides [8,9] and Zr [18][19][20].…”

Effects of aluminised-coating on microstructure and properties of Ni–Co-base superalloys

“…Han et al 21 found that the deformation mismatch between the substrate and coating may easily lead to crack initiation and failures under the actual long-term creep process. However, the most accessible literature 22 was based on laboratory studies, which included diverse damage mechanisms under specific loads. Meanwhile, the performance of aluminised-coating under combined oxidation and flow stress, which corresponded to realistic service conditions, was hardly considered in the previous work.…”