Reaction synthesis of Ni-Al-based particle composite coatings

Abstract

Electrodeposited metal matrbdmetal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 volume percent aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEMj, and electron probe microanalysis @?MA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 to 1000"C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al . particle interfaces and concentrically around the original Al particles. Upon heating to the 500-600"C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (6OO-1OOO"C), diffusional reaction between NiAl and nickel produces (y')Ni3Al. The final equilibrium microstructure consists of blocks of (y')Ni3Al in a y(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminizes.

Carburization Behavior of Electrodeposited Ni3 Al–CeO2-Base Coatings on Fe–Ni–Cr Alloys

“…These pores were formed owing to local densification during formation of Ni-Al intermetallic phases and fast diffusion of Al into the Ni matrix. 25,26 During high-temperature exposure, the rapid outward diffusion of substrate elements (e.g., Fe and Cr) and a self-sintering mechanism lead to the healing of pores in all coatings as described in our previous studies. 20,27 This porehealing is found to start at the coating/substrate interface, and gradually Fe-Ni-Cr Cr 23 C 6 (m), Cr 7 C 3 (m)…”

Effect of pre‐oxidation on coke formation and metal dusting of electroplated Ni3Al–CeO2‐based coatings in CO–H2–H2O

“…Significant numbers of pores (round dark phases in Fig. 1) in all annealed coatings were formed due to local densification and rapid diffusion of Al into the Ni matrix [20,21]. Figure 2c shows that the a-Al 2 O 3 scale is thin (1-2 mm thick) and compact.…”

Reactive oxide-dispersed Ni3Al intermetallic coatings by sediment co-deposition

“…The formation of intermetallic phases in Ni-Al binary composite coatings during the annealing treatment results from interdiffusion between Al particles and the Ni matrix, and is affected by the Al content, and the annealing temperature and time [22,23,25]. The phase structures in the fully annealed Ni-Al composite coatings obviously depend on the Al content in the coatings.…”

“…It can offer a simple way to apply reactive oxide-dispersed protective coatings on various substrates. Moreover, the CED technique was introduced to produce Ni-Al binary alloy coatings [22][23]. Ni-Al composite coatings can be co-deposited when Al metal particles are added to the nickel plating bath.…”