Exposure to Nanoparticles in Thermal Spraying — Vigilance Towards the Operator and the Outside Environment

This paper presents the results of an emission study on plasma spraying equipment and processes. Various measurements and samples were taken outside the spraying booth, at the operator level, and in the suction ducts upstream and downstream of the filtration equipment, creating a detailed profile of the aerosol emitted by the injection of NiAl powder in the plasma jet. The results show the existence of two families of particles, one ranging in size from 0.5 to 20 µm, the other of nanometric proportions. Concentrations of the larger particles were in the range of 600 cm-3 in the booth. As for submicron particles, concentrations of up to 107 cm-3 were observed but decreased significantly at the outlet of the filter system. The aerosol samples examined were dominated by a nanometric background of aggregates made up of oxidized nickel particles. Aggregates up to 100 nm in size, consisting of finer particles in the 5-20 nm size range, were found in high concentrations upstream of the filtration system. Great vigilance is thus required to protect equipment operators, an important part of which is placing dust collectors as close as possible to spraying booths connected by short, straight pipe runs.

MODIFICATION OF THE SURFACE LAYER OF SINTERED DUPLEX STAINLESS STEELS THROUGH ALLOYING USING THE GTAW METHOD

The demand for materials obtained using powder metallurgy (PM) is constantly increasing, especially on SDSSs, which are characterized by a two–phase structure consisting of ferrite and austenite. The main purpose of this study was to examine the effect of surface layer alloying with chromium carbide on the microstructure and tribological properties (e.g., hardness and wear resistance) of SDSSs. The multiphase sinters were prepared from two types of water–atomized steel powders: 316L and 409L. The technique of the APS method was used to deposit Cr3C2–NiAl powder on the SDSS surface. Electric arc (GTAW method) was used for surface alloying. Optical and scanning microscopy, X–ray phase analysis, and examinations of microhardness and coefficient of friction were performed in order to determine the microstructure and basic properties of SDSS after alloying. The surface alloying with Cr3C2 improves tribological properties of SDSSs such as hardness and the coefficient of friction.

Fabrication NiAl/Cu Composite Powder for Thermal Spray Coating

The NiAl/Cu feedstock powder was prepared by Cu coating on NiAl powder using electroplating technique. The NiAl (NS450, Metco Sulzer) powder was deposited Cu+ from CuSO4 solution at cathode with vary time process (60, 80 and 100 min). The microstructure and element of NiAl/Cu powders were investigated by scanning electron microscope (SEM) and energy dispersion of X-ray (EDX). The morphology of powder were appeared the Cu element holding all of surface NiAl particles. The chemical composition in powder using X-ray diffraction were presented the Cu phase with time process. The phase compounds were presented the Ni, Al and Cu phases. Then, it was appeared the new phase of Cu2O at 100 min time deposited. Therefore, it was low contentThe EDX analysis was supported the Cu cover on the surface NiAl powder. In SEM micrograph of NiAl/Cu cross-section coating were presented the completed structure coating of thermal spray technicque. In addition, the Cu content was improved melted particles by investigated increased lamellar of materials. The Cu lamella was distributed between Ni layers. It was confirmed that NiAl/Cu feedstock powder was fabricated by simple technique.

Friction and Wear Properties of αAlB12-NiAl Cermet Prepared by Spark Plasma Sintering

In this study, αAlB12-20vol% NiAl cermet disk specimens were prepared by spark plasma sintering, and their microstructure, Knoop hardness, fracture toughness, and friction and wear properties were investigated. The αAlB12-20vol% NiAl disk specimens were obtained by spark plasma sintering blended αAlB12 and NiAl powder at 1573 K for 600 seconds. No reaction product phases were observed between the αAlB12 and NiAl phases. The αAlB12-20vol% NiAl disk specimens exhibited friction coefficients lower than 0.2 and specific wear rates as low as 1.3 × 10-6 mm3/Nm when sliding against Si3N4 ball specimens in water. O-rich phases were observed on the worn surfaces of the NiAl and αAlB12-20vol% NiAl disk specimens after sliding against Si3N4 ball specimens in water. The Knoop hardness of the disk specimens was as high as 10 GPa and the fracture toughness was as high as 7 MPa m1/2.

Mikrostruktur dan Karakterisasi Sifat Mekanik Lapisan Cr3C2-NiAl-Al2O3 Hasil Deposisi Dengan Menggunakan High Velocity Oxygen Fuel Thermal Spray Coating

Surface coating processing of industrial component with thermal spray coatings have been applied in many industrial fields. Ceramic matrix composite coating which consists of Cr3C2-Al2O3-NiAl had been carried out to obtain layers of material that has superior mechanical properties to enhance component performance. Deposition of CMC with High Velocity Oxygen Fuel (HVOF) thermal spray coating has been employed. This study aims to determine the effect of powder particle size on the microstructure, surface roughness and hardness of the layer, by varying the NiAl powder particle size. Test results show NiAl powder particle size has an influence on the mechanical properties of CMC coating. Hardness of coating increases and surface roughness values of coating decrease with smaller NiAl particle size.

DENSIFICATION AND GRAIN GROWTH OF NANOCRYSTALLINE NIAL POWDER DURING PRESSURELESS SINTERING

Nanocrystalline NiAl powder was prepared by mechanical alloying. The prepared powder was cold compacted and sintered at different temperatures and times. The crystallite size of green and sintered compacts was estimated from X-Ray Diffraction peak profile analysis. Thereafter, the Generalized Parabolic Grain Growth model and Master Sintering Curve concept based on Combined Stage Sintering model were employed to investigate the grain growth and densification behavior of nanocrystalline NiAl powder during sintering, respectively. The results of modeling were in a very good agreement to that of experiment. Finally, by comparing the modeling results the sintering parameters were optimized.