Characterization of Nitrocarburized Coating by Plasma Electrolytic Saturation

Abstract

Plasma electrolytic saturation (PES) is an atmospheric pressure plasma deposition which is used for fabrication of nanostructural coatings. This process starts with the appearance of some sparks on the surface and finally by the formation of plasma envelope around the sample, particles and free radicals bombard the surface and diffusion takes place into the work-piece. In this paper, the effect of frequency (500, 1000 and 10000 Hz) as pulse parameters on properties of nitrocarburized layers deposited on AISI 1045 steel were investigated. The analytical characteristics of the coating were assessed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The corrosion behavior of coatings was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. Moreover, the microhardness and wear resistance of coated samples were also studied. The results indicated that applying nitrocarburized layer in all cases, improved the corrosion resistance, microhardness and also wear resistance of the substrate. The coatings treated at the frequency of 10000 Hz, had corrosion resistance about 2.4 and 1.4 times higher than those of the samples prepared at the frequency of 500 Hz and 1000 Hz. The surface hardness of 10000 Hz treated sample was about 1040 Vickers, which was more than those of the two other ones. An increase in frequency also caused wear resistance to increase.

Plasma Electrolytic Nitrocarburizing of SAE 1045: Electro-chemical Slurry Erosion Wear Analysis

“…The electrolyte and initial parameters to obtain the PEN/C coatings were based on the article by Noori and Dehghanian 5 . The electrolyte used (20 L) after the initial adjustments was composed of 6 gL -1 of C 3 H 8 O 3 (glycerol) and 24 gL -1 of NaNO 2 (sodium nitrite).…”

“…After this procedure, the samples were immersed for 5 min in acetone. The cleaning and chemical stripping procedure followed the recommendation of other authors 5 . The phases formed in the coating were determined by a Bruker model D8 ADVANCE diffractometer with Cu-Ka incident radiation (l = 0.15418 nm), and measurements were conducted with Bragg-Brentano θ -2θ geometry (step size = 0.020; power = 40 kV -40 mA; and time per step = 384 s).…”

“…XRD analysis detected the formation of iron nitrides ε -Fe 2 -3 N (JCPDS NO: 01-083-0878), γ' -Fe 4 N (JCPDS NO: 01-083-0879) and Fe 3 C (JCPDS NO: 03-065-2415). Also detected was Fe(Fe(C 9 N) 6 ) 3 5 . Therefore, the presence of these phases suggests that the concentration of carbon and nitrogen in the surface layers was so high that it had exceeded the solubility limits of carbon and nitrogen in iron, forming this protective coating on the samples surfaces 30 .…”

“…The plasma envelope is formed around the surface, which induces the bombardment of particles and free radicals on the surface. Thus, diffusion occurs on the surface of the sample 5 .…”