Effects of aluminizing on the microstructure and wear resistance of AISI 321 steel

Abstract

To enhance the surface properties, particularly hardness and wear resistance, of AISI 321 steel, an aluminizing coating was introduced through pack cementation treatment. Microstructure characterization and wear resistance tests were conducted to elucidate the intricate relationship between the microstructure and wear behaviors. A thorough analysis on the structure and compositions revealed the incorporation of FeAl(Cr) phases, aluminum oxides, titanium compounds and B2-NiAl phases in the coating, which resulted in a remarkable 192 % increase on the surface hardness, elevating it from 226 HV to an impressive 662 HV. In comparison to the uncoated 321 steel, the aluminized counterpart exhibited a pronounced reduction in coefficients of friction (COFs), wear volume losses, and wear rates. The wear mechanisms of both the uncoated 321 steel and aluminized steel were intricately analyzed. The uncoated 321 steel endured severe adhesive and oxidation wear, characterized by pronounced plastic deformation, the presence of wear debris and flaking oxides. In contrast, the aluminized steel predominantly underwent abrasive wear, showcasing a relatively smooth worn surface and dense continuous oxides. These findings not only reveal the significant enhancement of tribological properties by aluminized coatings, but also provide valuable insights into their fundamental behavior during wear.