Properties of an FeWCrMoBC Metallic Glass Coating on Grade 35 Steel

Abstract

To deposit metallic glass coatings, it is necessary to achieve high melt cooling rates. The FeWCrMoBC composition has a high melt viscosity and a sufficient glass-forming ability to fix an amorphous state at the cooling rates achieved during electrospark alloying using a crystalline electrode. The purpose of the work is to perform single-stage deposition of an amorphous coating by electrospark alloying using an as-cast FeWCrMoBC crystalline anode and to study the properties of the modified surface of grade 35 steel, namely, wettability, heat resistance, and tribological properties. The structures of the anode and the deposited coatings were studied by X-ray diffraction analysis using CuKα radiation on a DRON-7 diffractometer. Unlike the X-ray diffraction patterns of the anode material, the X-ray diffraction patterns of the coatings do not have sharp Bragg reflections and have a rather wide halo in the angular range 2θ = 40°–50°, which indicates their amorphous structure. Cyclic heat resistance tests are carried out at a temperature of 700°C for 100 h. The wear resistance and coefficient of friction of samples are studied during dry sliding friction at a speed of 0.47 m/s and a load of 25 N relative to a counterbody made of R6M5 high-speed steel. The effect of electric pulse ratio on the character of mass transfer (anode erosion, cathode increment, mass transfer coefficient) during coating formation is investigated. When the discharge pulse ratio decreases by 9 times, the erosion of the anode increases by 5 times and the cathode weight increment increases by 2.2 times. The maximum mass transfer coefficient is achieved at the highest pulse ratio. The following surface properties of grade 35 steel increase after coating deposition: the surface hardness of the samples increases by 2.3–2.6 times the average coating thickness is in the range 56–80.6 μm, the contact angle is in the range 108.4°–121.3°, the coefficient of friction decreases by 1.2–1.4 times, the wear resistance increases by 2–3.3 times, and the oxidizability in air decreases by 14–18 times. The achieved higher properties (hardness, wear resistance, heat resistance, hydrophobicity) of the operating surfaces of grade 35 steel parts after applying the proposed coatings can be used in various branches of machine-building production. The results obtained confirmed the possibility of deposition of metallic glass coatings onto grade 35 steel by electrospark alloying using an FeWCrMoBC anode material.