Surface Characterization and Corrosion Resistance of 36Cr-Ni-Mo4 Steel Coated by WC-Co Cermet Electrode Using Micro-Electro Welding

Abstract

Abstract:In this paper the influence of spark energy on corrosion resistance, hardness, surface roughness and morphology of WC-Co coated 36Cr-Ni-Mo4 steel by Micro-Electro Welding (MEW) was investigated. Frequencies of 5, 8 and 11 kHz, currents of 15, 25 and 35 A and duty cycles of 10, 30 and 50 % were applied for coating of the samples using a WC-Co cermet electrode. The results indicate that increasing the current, Duty cycle and frequency of the process increases spark energy. As spark energy increases, efficiency of coating increases to 80% and then decreases. X-ray diffraction (XRD) analysis was used to identify the phases. The results indicated that other than the peaks obtained for the metallic Iron with BCC (Body Centered Cubic) structure, Tungsten Carbide, Cr 7 C 3 and Titanium Carbide phases were also seen on the surface. Vickers micro hardness method was used for hardness measurement of the samples. Surface hardness increases to 817.33 HV0.05 with spark energy increasing up to 1.03 mJ, and then reducing. Optical Microscopy (OM) and scanning electron microscopy (SEM) to study Microstructural and atomic force microscopy (AFM) to study the topography, morphology and roughness were used. Polarization technique in 3.5 wt % NaCl solution was used to evaluate the corrosion properties. The results of the energy dispersive X-ray spectroscopy (EDS) analysis indicate that with increasing spark energy, the amount of Tungsten in surface increases to 41.95 wt % and then decreases. As spark energy increases up to 2.17 mJ, thickness of coating increases to 8.31 µm and then decreases. As spark energy increases, surface roughness is also increased. Corrosion test results indicated that the lowest corrosion rate (2.6 × 10 −8 mpy) is related to the sample with the highest level of efficiency.

Cermets and Hardmetals

“…The current special issue, with a focus on cermets and hardmetals, brings together seven scientific research papers [1][2][3][4][5][6][7] that investigate various aspects of these materials. The papers are broadly divided between WC-based hardmetal systems [1][2][3][4], lower density carbides including TiC [5] and NbC [6], and mixed oxide-carbide systems [7]. In two examples, the hardmetal is present as a thin coating on Cr-Ni-Mo based steel substrates [3,4].…”

“…The papers are broadly divided between WC-based hardmetal systems [1][2][3][4], lower density carbides including TiC [5] and NbC [6], and mixed oxide-carbide systems [7]. In two examples, the hardmetal is present as a thin coating on Cr-Ni-Mo based steel substrates [3,4]. There is a strong emphasis among these articles on the evaluation of the material's corrosion behavior [2][3][4][5], highlighting the importance of corrosion resistance in a great many applications, along with their tribological responses [3,7], mechanical behavior [1,4,6,7], and the influence of grain size for near-nano variants [1,2].…”