Self-fluxing Powder Research Articles

A Study on Wear Behaviour of NiCrBSi Flame Sprayed Coatings

TThe present study is an attempt to observe and evaluate the dry rolling wear behavior [1] of three types of Ni-base coatings on an Amsler type wear machine, against low-alloyed steel discs. The tested coatings were obtained by flame spraying (on the same low-alloyed steel substrate as the discs) using commercial Ni-base self-fluxing powders: 1060-00 and 1355-20 type (manufactured by Hoganas) and JK 586 type (manufactured by Deloro Stelite Co). In order to increase the strength of the layers, the deposition was followed by fusing [2]. The tests were conducted on pairs of coated – uncoated discs at the same load and the same speed in all three cases. In order to evaluate the wear behavior, there were observed and measured the surface roughness and the rolling path profiles. A severe wear regime with adhesion as the main phenomenon was observed in case of the low-alloyed steel discs.

Microstructures and wear properties of laser cladding Co-based composite coatings on Ti–6Al–4V

Abstract Metal matrix composite (MMC) coatings were fabricated on Ti–6Al–4V titanium alloy by laser cladding. Co42 self-fluxing powder, B 4 C, SiC and Y 2 O 3 were employed as the cladding materials. Microstructures and the wear properties of the different composite coatings were investigated comparatively. Results showed that the laser cladding coatings were mainly reinforced by CoTi, CoTi 2 , NiTi, TiC, TiB 2 , TiB, Cr 7 C 3 and Ti 5 Si 3 . The micro-hardness of the cladding coatings were equivalent to 3–4 times the Ti–6Al–4V substrate. Laser cladding coating exhibiting outstanding wear resistance was fabricated with the addition of 20 wt.% B 4 C, 7 wt.% SiC and 1 wt.% Y 2 O 3 . The wear resistance was enhanced by over 10 times compared with the substrate. However, with more SiC addition (14 wt.%), a higher micro-hardness was obtained together with poor wear resistance. The wear mechanism of the coatings was discussed by referring to the microstructures and the wear morphologies.

Air plasma sprayed coatings of self-fluxing powder materials

The article discusses the structural features of self-fluxing coatings obtained by plasma spraying air from entering the hub ring and the gas-dynamic focusing powder. It was shown that, unlike the unilateral spot powder inlet into the plasma jet, the use of the annular input node allows to increase heating efficiency and to accelerate the particles in the plasma stream. By optical and scanning electron microscopy that most of the particles forming the coating, in the plasma jet is in a molten or plasticized condition. Transmission electron microscopy revealed that high cooling rates of such particles contribute to the formation of γ-SMC supersaturated solid solution Ni-based average grain size of 80 nm.

NiCrSiB Thermal Sprayed Coatings Refused under Vibratory Treatment

The influence of mechanical vibrations on microstructure and some properties of Ni-based thermally sprayed and fused coatings deposited on a steel substrate has been studied. Self-fluxing powder with about 67 % Ni was used as a sprayed material. As-sprayed coatings were refused using conventional flame technique and with introducing of mechanical vibrations. During investigation of coatings by different methods it was found that vibratory treatment influences the solidified microstructure, corrosion resistance, microhardness, and surface state. It was found that in addition to thin planar solidification layer, obtained near the interface in conventional coatings, vibrations promote the forming of relatively thick boride-free layer. Several possible mechanisms are presented. Corrosion resistance tends to be improved with increasing of amplitude or frequency of vibratory treatment. The application of vibrations in set range has also allowed reducing coatings roughness up to 3 times. Comparison of results showed that vibrations amplitude proved as more effective parameter of vibratory treatment. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.3386

Plasma-arc spray-coating of powders of self-fluxing iron-base alloys 1. Estimation of the temperature and velocity of powder particles in the plasma flow

Mathematical simulation has been used to estimate the effect of technological factors on the variation of the temperature and velocity of particles of self-fluxing iron-base powder in a plasma flow of propane-butane combustion products. The influence of the plasma generator arc current, the flow rates of the plasma-forming gases and their relations, the powder particle size, the diameter of the plasma generator nozzle, the powder flow rate, and the spraying distance are analyzed. Optimal spraying conditions are determined for various powder fractions.

Structure and properties of gas-flame coatings of self-fluxing iron-base powder

Structure and properties of gas-flame coatings of self-fluxing iron-base powder

Special features of laser-powder deposition of self-fluxing powders of different fractions

(1990). Special features of laser-powder deposition of self-fluxing powders of different fractions. Welding International: Vol. 4, No. 5, pp. 388-389.

Wear resistance of detonation coatings of nichrome base powders in dry sliding friction

In the present work we investigated the wear resistance of two types of tungstenless detonation coatings devised at the Institute of Materials Science of the Academy of Sciences of the UkrSSR: the heat-resistant coatings (with working temperature up to 1000~ PNKhAI and PNKhAI-LB based on nichrome, wear-resistant coatings (with working temperature up to 720~ PKTSR3, and also PG--AN-9(TU IES 374-83) based on self-fluxing powders. The investigated materials were meant to replace the expensive and scarce coatings based on tungsten carbide which are very brittle and have a limited working temperature (to 540~ [I].

Physicomechanical characteristics of wear resistant coatings

1. A study was made of the effects of temperature and induction heating rate on the hardness, wear resistance, and bend strength of coatings produced from a self-fluxing powder of a nickel base hard alloy by the methods of centrifugal sinter-bonding and weld deposition. 2. It is shown that the relationships investigated are represented by curves with maxima and that the variation of the properties of such coatings is controlled primarily by changes in their density and structure. 3. The test results obtained demonstrate that increasing the rate of induction heating improves the mechanical properties of sinter-bonded coatings by shortening the time during which the powder is exposed to air and by intensifying the activating effect of the structural defects of the powder at higher sintering temperatures. The mechanical characteristics of coatings produced by sinter-bonding the powder under optimum conditions are higher than those attainable in coatings deposited by a technique in which the powder is melted. At high rates of heating, a coarse carboboride phase and a hypoeutectic zone of low wear resistance become dominant in the structure of weld-deposited coatings, adversely affecting the latter's properties. 4. As a result of the investigation described, the optimum conditions have been determined for the sinter-bonding and sintering of coatings at various heating rates; coatings produced under these conditions combine satisfactory bend strength, good wear resistance, and high hardness with adequate adhesion (15–20 kg/mm2) between the coatings and the basis metal.