Pulsed plasma deposition of Fe-C-Cr-W coating on high-Cr-cast iron: Effect of layered morphology and heat treatment on the microstructure and hardness

Abstract

Pulsed plasma treatment was applied for surface modification and laminated coating deposition on 14.5wt%-Cr cast iron. The scopes of the research were: (a) to obtain a microstructure gradient, (b) to study the relationship between cathode material and coating layer microstructure/hardness, and (c) to improve coating quality by applying post-deposition heat treatment. An electrothermal axial plasma accelerator with a gas-dynamic working regime was used as plasma source (4.0 kV, 10 kA). The layered structure was obtained by alternation of the cathode material (T1-18 wt% W high speed steel and 28 wt% Cr-cast iron).

Evaluation of the Microstructure, Tribological Characteristics, and Crack Behavior of a Chromium Carbide Coating Fabricated on Gray Cast Iron by Pulsed-Plasma Deposition

“…The microstructure of the substrate (gray cast iron) consisted of ferrite grains with an average microhardness of 223 ± 25 HV and graphite lamellae of 0.5–3.0 μm thickness ( Figure 1 a). The microstructure of the cathode (hypoeutectic cast iron) was composed of solid-solution pre-eutectic dendrites surrounded by eutectic Cr-rich M 7 C 3 carbides ( Figure 1 b) [ 42 ]. Hexagonal rod-shaped eutectic carbides with a volume fraction of 34–35 vol.% coalesced into agglomerates of 1–4 μm size.…”

“…Pulsed-plasma deposition was performed on an electrothermal axial plasma accelerator. EAPA was an arrester in the form of a paper-reinforced bakelite tube of 430 mm length, 8 mm inner diameter, and 17 mm wall thickness [ 42 ]. It was connected to an electrical circuit consisting of a capacitive energy storage device of 1.5 mF capacity [ 40 ].…”

“…Pulsed-plasma deposition was performed in the air with the following parameters: voltage stored in the capacitor = 4.0 kV, distance between EAPA electrodes = 50 mm, distance from the EAPA edge to the target surface = 50 mm, pulse number = 10. The as-deposited specimens were subjected to a post-plasma heat treatment (two hours of holding at 950 °C) followed by oilcooling [ 42 , 46 ]. During heating, the coating was covered by coal to prevent surface oxidation and decarburization.…”

“…Kolyada et al [ 40 , 41 ] highlighted the applicability of high-dynamic pulsed plasma flow generated in an electrothermal axial plasma accelerator (EAPA) for metallic surface modification. The design and operational principles of EAPA, which operates under atmospheric conditions, are outlined in detail in earlier studies [ 40 , 41 , 42 ]. Furthermore, EAPA was used for the surface structure modification (case hardening) of steel [ 43 ] and GCI [ 44 ].…”

Simulation of structure formation in the Fe–C–Cr–Ni–Si surfacing materials

“…Paper [6] shows that the highest level of wear resistance of cast irons is reached in the presence of matrix with a structure of metastable austenite. To increase wear resistance, cast irons are additionally alloyed with strong carbide-forming elements, such as Ti, V, Nb, Mo [7], and the rate of crystallization is also increased [8]. Improving the properties of cast iron products is reached by using a heat treatment that includes both the techniques of volume hardening and the technologies of surface modification by the sources of concentrated energy [9].…”