Influence of heat treatment on tribological properties of electroless Ni–P and Ni–P–Al2O3 coatings on Al–Si casting alloy

✍ Scribed by M. Novák; D. Vojtěch; T. Vítů

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 441 KB
• Volume: 256
• Category: Article
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2009.11.057

✦ Synopsis

Evolution of tribological properties of electroless Ni-P and Ni-P-Al 2 O 3 coating on an Al-10Si-0.3Mg casting alloy during heat treatment is investigated in this work. The pre-treated substrate was plated using a bath containing nickel hypophosphite, nickel lactate and lactic acid. For preparation of fiberreinforced coating Al 2 O 3 Saffil fibers pre-treated in demineralised water were used. The coated samples were heat treated at 400-550 8C/1-8 h. Tribological properties were studied using the pin-on-disc method. It is found that the best coating performance is obtained using optimal heat treatment regime (400 8C/1 h). Annealing at higher temperatures (450 8C and above) leads to the formation of intermetallic compounds that reduce the coating wear resistance. The reason is that the intermetallic phases adversely affect the coating adherence to the substrate. The analysis of wear tracks proves that abrasion is major wear mechanism, however due to the formed intermetallic sub-layers, partial coating delamination may occur during the pin-on-disc test on the samples annealed at 450 8C and above. It was found that fiber reinforcement reduces this scaling and increases wear resistance of coatings as compared to the non-reinforced Ni-P coatings.