Deposition of NiAl/Al[sub.3]Ni[sub.2] Coatings from Ni, Al and CrB[sub.2] Powders Using Mechanical Synthesis in Planetary Ball Mill

• Published in: Materials Vol. 17; no. 2
• Main Authors: Szlezynger, Maciej, Toboła, Daniel, Morgiel, Jerzy
• Format: Journal Article
• Language: English
• Published: MDPI AG 01-01-2024
• Subjects: Hardness; Intermetallic compounds; Mechanical properties; Powders; Poland
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17020492

Interest in composite thick coatings with an intermetallic matrix stimulates the development of new deposition techniques like the co-milling of pre-alloyed NiAl powder with platelet-shaped substrates. Obtained coatings were up to several micrometers thick as cold-welding of intermetallic particles was effective only at the start of this process, while later, chipping prevailed over added material. The present experiment covered the co-milling in the planetary ball mill of Ni and Al elemental powders (1:1 molar ratio) with AISI 304 steel platelets for 32 h at 300 rpm. Next, this process was repeated with an admixture of 15 wt.% of CrB[sub.2] powder. In both cases, their milling succeeded in producing up to a 200 μm coating after 4 h. The use of light, scanning and transmission electron microscopy (LM/SEM/TEM) helped to establish that the coatings had gradient microstructures with more refined crystallites of NiAl, Al[sub.3]Ni[sub.2] and CrB[sub.2] closer to the surface. With the addition of a ceramic phase, the coatings presented higher hardness and lower friction during dry wear tests both at RT and at 500 °C.