We apply the first-principles calculations to investigate the influence of Cr and Y on the oxidation resistance of RuAl(1 1 0) surface. Four possible oxygen adsorption sites: Al-top, Ru-top, Ru-bridge and Al-bridge are considered. It is found that the capacity of oxidation resistance of Ru is stronger than that of Al. Oxygen atom is adsorbed on the Ru-bridge site because of the strong charge interaction between Ru and the O. Importantly, the calculated adsorption energy of Cr-doped RuAl(1 1 0) surface is −0.350 eV, which is smaller than that of Ru-bridge site. The calculated result indicates that Cr-dopant can improve the oxidation resistance of RuAl(1 1 0) surface. The reason is that Cr-dopant improves the localized hybridization between Cr atom and the O atom, and weakens the charge interaction of Ru-O atoms and Al-O atoms. Therefore, we predict that Cr is a beneficial element to improve the oxidation resistance of RuAl thermal barrier coating.

Origin of the antioxidation mechanism of RuAl(1 1 0) surface from first-principles calculations

In the present study, two different types of coatings such as Cobalt (Co-Cr-W-C) and Nickel (Ni-Cr-B-Si-C) based layers have produced using a high power of Ytterbium-doped yttrium aluminum garnet (...

Laser cladding process of Cobalt and Nickel based hard-micron-layers on 316L-stainless-steel-substrate

Erosion tribo-performance of HVOF deposited Stellite-6 and Colmonoy-88 micron layers on SS-316L

In this work, an experimental study is conducted on the microstructure and mechanical properties of NiCrBSi and NiCrBSi reinforced with WC coatings, produced onto mild steel substrate by flame spraying technique. The resulting layers were analyzed using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. Roughness measurements were made using a roughness measuring system. Microhardness tests were carried out using a microdurometer operating with Vickers indenter and the load being 3N. The results show that the microstructure contain some inhomogeneities such us pores, microcracks for the composite coating and oxides. The XRD analysis reveal that the phases present within the coatings are different from the initial powders. In addition, the presence of WC hard particles makes the hardness of the composite coating much higher than the metal alloy.

Microstructure and mechanical characterization of NiCrBSi alloy and NiCrBSi-WC composite coatings produced by flame spraying

Friction stir processing (FSP) is a new and exciting technique being extensively explored because of its thermo-mechanical surface modification which has the capability to enhance the mechanical, microstructural and tribological properties. Various studies were described on friction stir processed aluminium alloys using several reinforcement particles containing micro and nano size grains thereby the formation of homogeneous and identical microstructure. However, this review is mainly focused on Al-7075 alloy which is a potentially superplastic alloy for making metal matrix composites. In this review, the recent research progress in FSP is discussed in detail with particular emphasis on their preparing method, characterization and various mechanical properties including present challenges and future prospects. Though, a remarkable progress has been made during the past few years, the present status in materials processing is far from ideal, especially in obtaining desire composites by using single or dual reinforcements.

Recent research progresses in Al-7075 based in-situ surface composite fabrication through friction stir processing: A review

NiCrBSi is a Ni-based alloy universally recognized for its superior mechanical properties, attributed to the presence of hard-dispersed carbides and borides, which is dependent on the deposition technique. Moreover, Metal Matrix Composites (MMC) materials will aim to combine the resilience of metals with high wear resistance specific of ceramics which made them innovative for a large wide of wear resistance applications. In this paper, thick NiCrBSi and NiCrBSi-WC coatings are made ontoS235JR mild steel substrates using an oxyacetylene flame-spraying torch (SuperJetEutalloy, Castolin Eutectic). Two different wear tests: sand/wheel wear test in dry conditions and the pin-on-disc wear test in continuous motion are used to investigate addition effects of WC reinforcing ceramic phase on the microstructure and wear resistance of the coatings layers. The results show that the presence of ceramic phase affects the wear resistance of the coating. For both wear tests, the metallic alloy coating has an improved wear resistance than the reinforced ones. WC reinforcement does not play the protective role of the matrix against wear but improve the hardness. Wear mechanism is mainly controlled by the scratching and by the pull out of WC particles because of their faceted shape. Received 29 Aug 2016, Revised 01 Oct 2016, Accepted 04 Oct 2016

http://applications.umons.ac.be/docnum/c7b423fd-d183-486c-9cec-966066b9b364/CE221429-2420-4E10-A555-240170AFB73F/480-JMES-2937-Rachidi.pdf

Wear Performance of Thermally Sprayed NiCrBSi and NiCrBSi-WC Coatings Under Two Different Wear Modes

Surface coatings by thermal spraying technique are extensively used in various industrial fields where the wear and corrosion resistance is paramount. However, mechanical performances are not always satisfactory because of high porosity, cracks and weaker adhesion. NiCrSiB is a Nickel based alloy universally recognized for its superior mechanical properties, attributed to the presence of hard-dispersed carbides and borides, which is dependent on the deposition technique. This work is devoted to the discovery by experimental study of the morphology, microstructure and mechanical properties of thick NiCrBSi coatings synthesized onto a mild steel substrate S235JR prepared beforehand using an oxyacetylene flame spraying torch (SuperJetEutalloy, Castolin Eutectic). Composites materials will aim to combine the resilience of metals with high wear resistance specific of ceramics. In order to study the addition effects of a reinforcing ceramic phase on the microstructure and mechanical properties of the metal alloy, NiCrBSi coatings reinforced with tungsten carbide were also made. The resulting layers were analysed to study the evolution of the microstructure, the tungsten carbide dispersion in the nickel matrix, using characterization methods: optical microscopy, scanning electron microscopy coupled with EDS technique and Xray diffraction analysis. Roughness measurements of the substrates and as-sprayed samples were made using roughness measuring system TIME TR200. Microhardness tests were carried out using microdurometer LECO M-400-A operating with a Vickers indenter with a square base and the load being 3N. Furthermore, the addition effect of the reinforcing particles on the microstructure and the mechanical performances of the layers were investigated.The results show that the microstructure contain some inhomogeneities such us porosity, microcracks for the composite coating and oxides. The XRD analysis revealed that the phases present in the coatings are different from the initial powders. In addition, the presence of WC hard particles makes the hardness of the composite coating much higher than that of the metallic alloy.

Rachida Rachidi

Papers

Microstructure and mechanical characterization of NiCrBSi alloy and NiCrBSi-WC composite coatings produced by flame spraying

Wear Performance of Thermally Sprayed NiCrBSi and NiCrBSi-WC Coatings Under Two Different Wear Modes

Influence of reinforcement particles in MMC coatings made by flame thermal spray technology