Tribocorrosion Behavior of Various Coatings on Duplex Stainless Steel

Duplex steel pump plungers inside a piston pump working in harsh conditions require additively manufactured hard wear-resistant coating. Two types of hardfacing are compared for better tribocorossion behaviour aiming to reduce the failure rate caused by microstructurally-induced macroscopic anisotropy. Cylindrical plungers are performing constant reciprocating motion with 285 Rev/min. Lubricant selected is Shell Morlina 150; diameter of the plunger 76 mm; movement distance of the plunger 140 mm; linear velocity 1,3 m/s; working pressure – 180 bars; maximal temperature – 120^oC; medium is sour water (alkaline, with pH around 11, with traces of H₂S and NH₃). Plasma arc Directed Energy Deposition (DED-arc) with powder feedstock has been used for production of the machine parts with based metal X2CrNiMoN22-5-3 and two different outer layer: of WC /WOKA 3700 (with chemical composition - W Balance, Cr 24%, Ni 8%, C 6%, Fe<0.5%) and the other possibility - Nickel Balance, Cr 16%, B 3.3%, Si 4.2% Si, C 0.7% and a minor amount of Fe. The microstructural evolution and wear mechanisms were analyzed via optical microscopy and EDX microanalysis. Data is gathered with hardness measurement and subsequently is determined the service lifespan.

 In order to reduce the failure rate of the plungers, extra care is taken for assuring the metallurgical bonding of the base metal and the overlay. The hardness assessment is giving around 58-62 HRC. Microcracking detection is perfomed. The findings provide valuable insights into optimizing the tribological performance of coated duplex stainless steels in industrial machinery. Additive manufacturing DED-arc method gives possibility to obtain new materials which require intensive evaluation before putting into operation. Novel production techniques are proving to show superior materials characteristics while being much more cost effective.

Funding: The author acknowledges support from project BG16RFPR002-1.014-0005.