Characterization and evaluation of electroless nickel phosphorus composite coating

Abstract

Electroless NiP coating is an established surface treatment that newlinedeposits a uniform metal-phosphorus alloy layer on conductive and non newlineconductive substrates through an autocatalytic chemical reaction. This coating newlineoffers good abrasion and corrosion resistance due to its low porosity and high newlinehardness. However, producing NiP coatings is costly due to the high price of newlinechemicals and waste generation. While as-deposited amorphous NiP coatings newlinehave decent mechanical and anticorrosion properties, incorporating Alumina newline(Al2O3) nanoparticles can further enhance these attributes. The major limitation newlineof NiP coatings is the high production cost stemming from chemical expenses newlineand newlinemetal-bearing sludge waste. Incorporating inexpensive alumina newlinenanoparticles aims to improve the coating performance to mitigate this cost newlinedrawback. newlineNickel Phosphorous (NiP) and Nickel Phosphorous-Alumina newline(NiP-Al2O3) composite coatings reinforced with Al2O3 nanoparticles were newlineprepared on mild steel using an electroless deposition process. The coatings newlinewere heat treated at 400°C for 1 hour. Incorporating Al2O3 nanoparticles in the newlineNi-P matrix led to a reasonable increase in microhardness. Heat treating the newlinecoatings increased the hardness by 70.5% for NiP and 82.5% for NiP-Al2O3 newlinecompared to the as-deposited condition. This hardness improvement is newlineattributable to crystallization of amorphous nickel and formation of Nickel newlinePhosphide (Ni3P). The wear behavior of as-deposited and heat treated NiP and newlineNiP-Al2O3 coatings were studied under dry sliding conditions. The NiP coating newlinewear mechanism involved oxidation and adhesion. The NiP-Al2O3 coating wear newlinemechanism involved oxidation, adhesion, and abrasion due to the Al2O3 newlineparticles. newline