Effect of Heating Treatment on the Microstructure and Properties of Cr–Mo Duplex-Alloyed Coating Prepared by Double Glow Plasma Surface Alloying

Abstract

In this study, Cr–Mo duplex-alloyed coating was prepared on carbon steel by double glow plasma surface alloying (DGPSA). The effect of annealing and quenching and tempering (Q&T) treatments on the microstructure and performance of the coating was investigated by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), backscattering electron imaging (BSEI) and electron backscattering diffraction (EBSD) techniques. The results show that a gradient structured coating composed of an Fe–Cr–Mo solid solution (Fe–Cr–Mo SS) layer and an alloyed pearlite layer was obtained on the steel surface. The affected layer was adjacent to the coating. After annealing or Q&T, more carbides precipitated in the Fe–Cr–Mo SS layer and alloyed pearlite layer. Most of the C atoms in the subsurface were dragged into the coating to form carbides in the Fe–Cr–Mo SS and alloyed pearlite layers of the coating, transforming the affected layers into a carbon-poor zone. Annealing and Q&T hardly modified the thickness of the coating, but greatly changed the hardness and corrosion resistance of the coating. The Q&T treated samples had higher hardness and better corrosion resistance than the as-DGPSA treated and the annealed samples.

Evolution of the Microstructure and Properties of Pre-Boronized Coatings During Pack-Cementation Chromizing

“…This is because that a large fraction of B atoms react with the Cr atoms to form the Cr2B phase as a result of the further increase of Cr concentration. Meanwhile, the C atoms also move from the substrate to the coating, owing to the low carbon potential in the coating caused by the addition of carbide forming element Cr [13]. Consequently, the block-like chromium carbides CrxCy (Cr7C3 and Cr23C6) are formed.…”

“…However, single thermo-diffusion coatings usually only improve a certain property of the parts, and can't meet the demands of some mechanical parts (gears, shafts, etc.) working in severe environments, which are characterized by high-speed, cyclic heavy-load, and/or corrosiveness [11,13]. For example, the wear resistance of boronized sample (hardness higher than 1600 HV) can be strengthened greatly [14,15], but the corrosion resistance is still poor and is also accompanied by brittleness [14].…”

“…For chromized samples, studies have pointed out that there is a carbon-poor layer (hardness lower than the substrate) existing between the Cr coating and steel substrate [11,13,16,17]. Fortunately, it has been reported that these shortcomings can be avoided by duplex coating or composite coating treatments [18][19][20][21][22].…”

Duplex Treatment of AISI 420 Steel by RF-ICP Nitriding and CrAlN Coating Deposition: The Role of Nitriding Duration

“…Coating adhesion can strongly influence the corrosion behavior of coated steel, especially under different factors, such as aggressive environment and mechanical loading. Several methods, such as substrate heating, ion bombardment or mixing, deposition of gradient coatings, and others [5][6][7], are often used to enhance coating adhesion. However, hard coatings, e.g., nitride-based coatings such as CrN, TiAlN, CrAlN, and TiAlSiN, are not the only factors involved [8].…”

Microstructure and Tribological Properties of Self-Lubricating FeS Coating Prepared by Chemical Bath Deposition Coating Technique

“…Improving the wear resistance of gear materials mainly starts from two aspects: one is to improve the surface hardness of the gear material, and the other is to introduce a lubricating medium. For the 2 of 10 first, surface strengthening methods such as carburizing [10,11], nitriding [12,13], carbonitriding [14,15], thermal chromizing [16][17][18], electron beam surface treatment [4,16], electro brush-plating [5], double glow plasma surface alloying [19,20], or deformation induced martensite [21] are commonly used to improve the performance of the steel surface. However, the hard surface accelerates the wear of its counterpart and is ineffective in preventing strain fatigue of the substrate, which results in scuffing failure, especially under boundary lubrication of rubbing-pairs [22].…”