Corrosion Behavior of Spherical Chromium Carbide Reinforced NiCrBSi Hardmetal Coatings in Sulphuric Acid Solution

In the present work, four groups of spherical chromium carbide reinforced NiCrBSi hardmetal coatings were prepared on AISI 4145 steel by plasma transferred arc (PTA) technique. The corrosion behavior of the four as-received hardmetal coatings in 0.5 mol/L H2SO4 solution was investigated by polarization curve and electrochemical impedance spectroscopy (EIS). The results revealed that more Cr-rich carbides (Cr3C2, Cr7C3 and M23(C, B)6) are formed in the chromium carbide reinforced coatings, while for the NiCrBSi hardmetal coating only Cr7C3 carbide was detected by XRD. The polarization results show that the chromium carbide reinforced NiCrBSi hardmetal coatings have positive corrosion potential and lower corrosion current, providing a better protective effect to the substrate metal. The combined effects of Cr-rich carbide ceramic phases and a more stable passive film of Cr2O3 greatly improved the corrosion resistances of the chromium carbide reinforced NiCrBSi hardmetal coatings. The coating with the highest spherical chromium carbide addition has more pores because of the thermal stress due to the difference of thermal expansion coefficient between the NiCrBSi bonding phase and chromium carbide reinforced phase. The negative effects of the pores weaken the corrosion resistance, and the coating with the 30% chromium carbide content shows the best corrosion resistance. For NiCrBSi hardmetal coatings with higher reinforced chromium carbide content, the repeatability of the corrosion current obtained by polarization fitting is not as good as that of coatings with lower chromium carbide content. The repeatability of polarization results becomes worse when the specimens keep in a more stable passive state.

Wear Behaviors of Carbon–Chromium Carbide–Chromium Multilayer Coatings Prepared by Reactive High-Power Impulse Magnetron Sputtering

Carbon–chromium carbide–chromium multilayer coatings were deposited by utilizing reactive high-power impulse magnetron sputtering with alternating various ratios of ethyne and argon mixtures under a constant total deposition pressure, target pulse frequency, pulse duty cycle, average chromium target power, and total deposition time. Two different alternating gas mixture periods were applied to obtain films with different numbers of layers and lamination thicknesses. The results show that the reduction in the modulation period effectively affects the elastic modulus and the subsequent ratio of hardness to elastic modulus (H/E) of the whole coating, which helps adapt the elastic strain in the coating. This improves the adhesion strength and wear resistance of coatings at room temperature. However, with the increase in wear test temperature, the difference between the wear behaviors of two types of coatings becomes inconspicuous. Both types of coatings lose the wear resistance due to the decomposition of hydrocarbon and the oxidation of the chromium content in the films.

INFLUENCE OF DIBENZYL ETHER (DBE) ADDITION ON THE STRUCTURE OF CHROMIUM CARBIDE COATING OBTAINED BY THE MOCVD METHOD FROM COL “BARKHOS”

Investigations of the effect of the addition of dibenzyl ether (DBE) to the chromium organic liquid (COL) “Barkhos” on the structure and performance properties of chromium carbide coatings obtained by chemical deposition of their gas phase have been carried out. It is shown that the use of the DBE additive expands the temperature range for the formation of chromium carbide coatings with a horizontally layered structure, which are more resistant to corrosion and erosion wear. In this case, there is an increase in the adhesive strength and cavitation resistance of the coatings. The use of the DBE additive reduces the through porosity of the coatings. Coatings obtained with DBE additives have an abnormally high resistance to electrochemical dissolution in comparison with other materials used for work in corrosive environments.

High Pressure Sintering of Silicon Carbide with Mg-Cr3C2 Composite Additive

Porous silicon carbide was sintered at 1300 °C/30 MPa for 2 h with 4 wt.% magnesium alloy and 4 wt.% chromium carbide composite additives. The sintered ceramic presented density of around 92% of the theoretical density. No new phase was observed after sintering. Mg segregates around chromium carbide particles in sintered ceramic. The silicon carbide particles were mainly bonded by melt magnesium alloy and chromium carbide diffused in solid state. The voids existed in the sintered ceramic, but much more fracture occurred in silicon carbide particles during bending due to high bonding strength of sintering necks. Some voids existed in the ceramic, which act as crack sources during fracture.

Influence of Vanadium-Chromium Carbide on the Microstructure of Reinforced FeCrV15 Hardfacing during Laser Cladding Deposit

The increasing manufacturing technologies is a crucial aspect of industrialization. Laser additive manufacturing is the process of manufacturing using laser (heat) technology to manufacture component from scratch and or strengthening and modification of surfaces that are subject to abrasion. The combination of both Chromium Carbide (CrC) and Vanadium Carbide reinforced iron based hard facings have gotten progressively significant in enhancing the corrosion and wear resistance of tool subject to adverse abrasive and impact conditions. This study investigates the effect of vanadium-chromium carbide on the microstructure of the clad with respect to its laser processing parameters.