Inconel and micro and nano WC-12Co powders were deposited on AISI 4140 carbon steel by high-velocity oxy fuel (HVOF) coating and followed by laser surface modification. Laser power and scan speed were varied at different levels. Microstructure and microhardness were investigated. Nanocoatings performed better than microcoatings. Nanostructured WC powder coatings exhibited greater hardness compared to microstructured powder coating. When the laser power is increased to 170 W, a small cellular dendrite microstructure through multiphase solidification is formed due to the difference in thermal properties of Inconel 625 and WC particles. Adequate laser power and low scan speed were preferred to produce a high-quality coating. From the electrochemical corrosion test results, it was observed that the corrosion rate of laser-modified HVOF sprayed coating is lower than the carbon steel sample. This shows that the Inconel sprayed by laser-modified HVOF coating enhanced the corrosion resistance of the substrate steel material. The porosity percentage was higher for all the samples when laser scan speed was increased.
This paper reports the design and development of a Proton Exchange Membrane (PEM) fuel cell using open pore cellular metal foam as the flow plate material. Effective housing designs are proposed for both hydrogen and oxygen sides and through the application of Computational Fluid Dynamic (CFD) modelling and analysis techniques the flow regime through the open pore cellular metal foam flow plate are identified.
Based on the CFD results the best anode housing design was selected and manufactured. The fuel cell was assembled and tested and the findings are reported.
In the present study, TiN coatings were deposited with and without NiTi interlayer onto 316L stainless steel substrates to observe the effect of amorphous NiTi layer on the adhesion properties of TiN coatings. The deposition technique was carried out at a temperature (100–150°C) without any substrate heating to form the amorphous NiTi coating, using the closed field unbalanced magnetron sputtering system. The qualitative and quantitative adhesion properties of TiN coatings with and without amorphous NiTi interlayer were measured using the Rockwell C test, the scratch test and the pull-off test. This research demonstrates how the amorphous NiTi interlayer improved the adhesion of TiN coating when a thickness of the NiTi interlayer applied was equal to 0·5 μm. A thin layer of amorphous NiTi coating was shown to exert a significant influence over the adhesion performance of the TiN coatings and demonstrating its suitability for the tribological applications.
Abstract In this study, a design of experiment (DOE) approach is used to investigate the influence of powder size and mixing ratio on the microstructure and properties of thermal spray coatings. Nano and micro sized WC-12Co powders combined in different proportions with Inconel 625 were deposited on carbon steel substrates by HVOF spraying. The resulting coatings are examined and the effect of different powder combinations on hardness and yield strength is assessed. Spraying procedures and test methods are described and the findings are discussed. Of the various coatings produced, one shows great promise for wear protection, particularly in oil and gas applications.
The application of functionally graded materials (FGMs) is quite difficult, but thermal spray processes like Plasma spray have demonstrated their unique potential in producing graded deposits, where researchers have used twin powder feed systems to mix different proportions of powders. FGMs vary in composition and/or microstructure from one boundary (substrate) to another (top service surface), and innovative characteristics result from the gradient from metals to ceramics or non-metallic to metals. The present study investigates an innovative modification of a high velocity oxy-fuel (HVOF) thermal spray process to produce functionally graded thick coatings. In order to deposit thick coatings, certain problems have to be overcome. Graded coatings enable gradual variation of the coating composition and/or microstructure, which offers the possibility of reducing residual stress build-up with in coatings. In order to spray such a coating, modification to a commercial powder feed hopper was required to enable it to deposit two powders simultaneously which allows deposition of different layers of coating with changing chemical compositions, without interruption to the spraying process. Various concepts for this modification were identified and one design was selected, having been validated through use of a process model, developed using ANSYS Flotran finite element analysis. In the current research the mixing of different proportions of powders were controlled by a computer using LabVIEW software and hardware, which allowed the control and repeatability of the microstructure when producing functionally graded coatings.
'/%3e%3cpath d='M200 752.362h200v300H200z' style='fill:%23fff;fill-opacity:1;stroke:none' transform='translate(0 -752.362)'/%3e%3cpath d='M400 752.362h200v300H400z' style='fill:%23ff883e;fill-opacity:1;stroke:none' transform='translate(0 -752.362)'/%3e%3c/svg%3e)
'%3e%3ccircle r='20' fill='%23008'/%3e%3ccircle r='17.5' fill='%23fff'/%3e%3ccircle r='3.5' fill='%23008'/%3e%3cg id='d'%3e%3cg id='c'%3e%3cg id='b'%3e%3cg id='a' fill='%23008'%3e%3ccircle r='.875' transform='rotate(7.5 -8.75 133.5)'/%3e%3cpath d='M0 17.5.6 7 0 2l-.6 5L0 17.5z'/%3e%3c/g%3e%3cuse xlink:href='%23a' transform='rotate(15)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(30)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='rotate(60)'/%3e%3c/g%3e%3cuse xlink:href='%23d' transform='rotate(120)'/%3e%3cuse xlink:href='%23d' transform='rotate(-120)'/%3e%3c/g%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)