Papers by Keyword: Plasma Spray

Abstract: The plasma sprayed bronze coatings are widely used for repairing of plain bearing used in different applications. This type of coating was not deeply analyzed in state-of-art publications. In presented article we fill this gap in the case of plasma spraying process. The influence of power current (300/500/700A) and hydrogen flow (0/4/8 NLPM) on microstructure and thickness of aluminium bronze-polyester coating was investigated. The Thermico A60 plasma torch was used for thermal spray process of coating on flat carbon steel samples (grade S355). The Metco 604NS was sprayed with 20g/min powder feed rate. The obtained results showed the presence of local large pores formed by burning of polyester in plasma plume. This gap makes role of oil pockets in bearings. The obtained coatings were characterized by large deviation in thickness in range 200-350 micrometers. It might be concluded that in requires additional milling process after deposition.

Abstract: Titanium is widely used for medical purposes. It related to bone repair because of its favorable mechanical properties and biocompatible ability to osseointegrate in host bone tissue. A good and lasting connection of the implant with the bone tissue is possible when there are sufficient conditions for the bone to grow into the pores of the material, therefore the use of a porous titanium coating may be helpful in solving this problem. In this paper, shrouded plasma spray is used to produce low oxide containing titanium coatings and lower the cost as titanium is a very reactive metal at high temperatures. A solid conical shroud was designed for plasma spray. The titanium coatings were assessed by scanning electron microscopy and energy dispersive X-ray spectroscopy. An analysis in microstructure had been carried out. The results showed that the shroud attachment played an important role in protecting the titanium particles in flight during the process of plasma spraying. An enhanced microstructure with moderate porosity in the titanium coatings plasma sprayed with the shroud was observed. The reduction in air entrainment with the shroud resulted in a good heating of the particles. The plasma-sprayed titanium coating was mainly composed of α-Ti with a low quantity of TiO.

Abstract: In order to study the friction characteristics of the plasma spray modified layer on the surface of titanium alloy, the friction sub-combination consisting of three type enhanced Teflon as the pin sample was carried out in the artificial seawater environment. The results show that the friction coefficient and wear degree of the plasma spray surface treatment specimen are also lower than the TC4 titanium alloy substrate, the surface modification sample and the three enhanced Teflon side friction, the side wear is serious, the surface plasma spray modified titanium alloy needs to reduce its surface roughness before it can be used as a friction sub-type material.

Abstract: The bond coat plays an important role in the failure of the thermal barrier coating (TBC) system used for gas turbines ^{[1, 2]}. In this research, the CoNiCrAlY coated Ni-base superalloy specimens were used for developing evaluation method for interfacial damage in the coat. Samples were exposed at 1000°C and 1100°C for up to 1000 hours. The morphology and residual stress in the thermally grown oxide (TGO) layer on the CoNiCrAlY coating were characterized by microscopic observation and luminescence spectroscope, respectively. The microstructure and damage o\n both the coating surfaces and the cross sections were observed by optical microscope and scanning electron microscope. According to the results, the low pressure plasma sprayed CoNiCrAlY coating (LPPS) showed the thinnest TGO layer and lowest residual stress.Residual stress decreased with an increase in exposure time, depending on the morphology of TGO layer. The effects of thermal spraying methods on the oxidation of yttrium in TGO layer and BC layer and its influence on interfacial damage were discussed.

Abstract: Titanium and its alloys are often used as key materials for corrosion protection. A promising approach to optimize both mechanical properties and corrosion resistance is the use of coating technologies. In this paper, shrouded plasma spray was used as a useful technology to produce low oxide containing titanium coatings. A solid shroud was used to plasma spray titanium coatings to reduce the oxide content. The titanium coatings were assessed by optical microscope, scanning electron microscopy and Vickers microhardness testing. The results showed that the shrouded titanium coatings exhibited an enhanced microstructure. The presence of the shroud and shroud gas flow led to a significant reduction in coating porosity because the reduction in air entrainment with the shroud resulted in better heating of the particles. The shrouded titanium coatings had a lower value of Vickers microhardness and a relative lower standard deviation than the air plasma sprayed titanium coatings.

Abstract: Liquid wood is one of the newly discovered green polymer materials, being a biodegradable and recyclable thermoplastic, made from cellulose, lignin and natural additives, currently used in commerce as ARBOFIL, ARBOROM and ARBOBLEND. The applications of this material (aeronautics, automotive, construction, consumer goods etc.) are limited by two major drawbacks: higher weight compared to ordinary plastic materials and low melting point (≈ 175° C). In this work was studied the possibility of changing some mechanical and thermal properties of this material by applying superficial coatings. For this process were prepared specimens from two types of material: ARBOBLEND and ARBOFIL. The resulted samples were analyzed in terms of microstructural changes both longitudinally (in order to evaluate the quality of the deposited layer) and on cross section (in order to evaluate the changes produced at the interface substrate - coating). For this purpose were used the QUANTA 200 3D (FEI, Holland, 2009) scanning electron microscope and the X`PERT PROMD diffractometer (Panalitycal, Holland, 2009). Using the UMTR 2M-CTR Micro-tribometer were evaluated the elasticity modulus of the coatings through microindentation and its adhesion to the substrate through scratch method, applied both longitudinally and on cross section.

Abstract: Fe-C-W-Cr-Ni alloy powder in diameter of 32-53 μm made by argon atomization was low-pressure plasma sprayed to produce high Cr-Ni cast iron base deposits with finely dispersed tungsten carbide particles. The as-sprayed deposit produced on a non-cooled substrate was composed of γFe, αFe and carbide. The fine precipitates in the as-sprayed deposit were carbide. With increasing heat treatment temperature up to 1273 K, the carbide particles coarsened. The as-sprayed deposit produced on a non-cooled substrate had higher hardness than the heat-treated deposits. The wear resistance of the as-sprayed deposit produced on a non-cooled substrate was lower than that of heat-treated deposits. The as-sprayed deposit produced on a non-cooled substrate and heat-treated deposits had higher wear resistance than commercial stainless steel.

Abstract: Thermal barrier coatings have been widely used in in both energy and propulsion systems. Plasma-sprayed thermal barrier coatings have relatively high interconnected porosity and lamina structure, which bring out a low bond strength, and lead to a short thermal cycling life. Lasers can be used for modification of materials surface. In this paper, plasma-sprayed thermal barrier coatings were laser-glazed by a high power laser in order to modify the structures. The microstructure of laser-glazed TBCs is investigated. The change on surface roughness has been examined. The result indicates that a smooth and dense glazed surface with craters and a network of microcracks is obtained after laser-glazing. The laser-glazed region consists of a columnar microstructure. There are segmentation microcracks in the laser-glazed coatings, which don’t run through the coatings along thickness. Surface roughness has been reduced significantly for the laser treated ceramic coatings.

Abstract: Electromagnetic parameters of ultra-fine SiC, SiC whisker and nanometer SiC were tested to evaluate the microwave absorbing properties. Optimized nanometer SiC-CNTs/AT13 composite was fabricated by high energy mechanical commixture. Nanometer SiC-CNTs/AT13 absorbing coating was prepared by multi-functional micro-plasma spray system. Morphology and the structure of the powders were characterized by scanning electron microscope. The microwave absorbing characteristic of the coating was evaluated by measuring the reflection loss using an HP8757E scalar quantity network analyzer in the 2-18 GHz band range. The coatings were density, low porosity and uniform morphology. The reflection loss values of -10 dB are obtained in the 2~18GHz range. The minimum reflection loss of the coating is -13.12 dB at 12.64 GHz, and the bandwidth of the reflectivity below -5dB is 9.36GHz. It is indicated that the plasma spraying process is an effective way of preparing microwave absorbing coating.

Abstract: “Art is everywhere” to quote Ben, a renowned French contemporary artist. However, there are some areas in which art is more prevalent. Thermal spray is one of them, as this presentation seeks to demonstrate. For this, each of the arts (according to their official classification) is shown to correspond to a specific key point of the thermal spray process for coating: e.g., coating build-up, additive manufacturing, deposition onto brittle and/or temperature sensitive materials (glass, wood, fabrics, polymers), powder optimization, and adhesion. Both modeling and experimental aspects are discussed, focusing on the study of particle-to-particle or particle-to-substrate interfaces, shock phenomena and advanced investigation techniques such as X-ray microtomography or high-speed instrumentation. Plasma spray and cold spray provide the relevant examples that this contribution elaborates. They relate to different industrial sectors such as aircraft-aerospace, luxury, biomedical and the automotive industry. Beyond anecdotal evidence, the discussion aims to show that an artistic approach to thermal spray does help to understand better this powerful coating process.