Plasma nitriding effect on tribological and corrosion properties of Stellite 6 and 12 PTA weld clad hardfaced on stainless steel 410

Abstract

Cladded Stellites on steel substrates are utilized vastly in harsh environments. Since the plasma nitriding process can raise the tribological behavior of the material surface. Thus, the main purpose of this paper is to investigate tribological and corrosion characteristics of nitrided Stellite 6 and 12 that were cladded through a plasma-transferred arc (PTA) method on stainless steel 410. A Pin-on-disk tribometer, Tafel polarization, and electrochemical impedance spectroscopy were utilized to study the properties of various coatings. The X-ray diffraction patterns indicated that both cladded coatings mainly included solid solution phase (γ-Co) and chromium-rich carbide phases. However, after the plasma nitriding (PN) process, nitrided phases such as CrN, CoN, and W2N were found at the surface of coatings. The PN process caused a reduction in wear rates for both Stellite coatings by about 89–98%. This reduction was due to the hardness increase and the friction coefficient decrease. However, this PN process increased the corrosion rate of Stellites in a 3.5% wt NaCl solution. Such behavior was based on forming brittle and hard nitrided phases that promote surface cracks and open the path for ion corrosion penetration.