Metallurgical and Materials Engineering (E-Journal)
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Understanding plasma spraying process and characteristics of DC-arc plasma gun (PJ-100)
Full text linkThe thermal spray processes are a group of coating processes used to apply metallic or non-metallic coatings. In these processes energy sources are used to heat the coating material (in the form of powder, wire, or rod form) to a molten or semi-molten state and accelerated towards a prepared surface by either carrier gases or atomization jets. In plasma spraying process, the spraying material is generally in the form of powder and requires a carrier gas to feed the powder into the plasma jet, which is passing between the hot cathode and the cylindrical nozzle-shaped anode. The design of DC plasma gun (PJ - 100) is designed and manufactured in Serbia. Plasma spaying process, the powder injection with the heat, momentum and mass transfers between particles and plasma jet, and the latest developments related to the production of DC plasma gun are described in this article
The morphology of ductile cast iron surface damaged by cavitation
Full text linkThe study was designed to investigate the cavitation behavior of the ductile cast iron with microstructure consisting of spheroidal graphite in a predominantly ferrite matrix with 10% pearlite. The experiments were conducted using the ultrasonically induced cavitation test method. The frequency of vibration and the peak-to-peak displacement amplitude of the horn were 20 ±0.5 kHz and 50μm, respectively, with separation of 0.5 mm between the sample and the horn tip. In order to obtain the erosion curve, the mass loss measurements were performed after each exposure interval. The mass loss was recorded every 30min for a test period of 240 min. Roughness parameter Ra (the mean roughness), was used to characterize the surfaces. The cavitation rate was 1.85 higher for ductile iron compared with that of carbon steel with similar hardness, because graphite removal produces high stress concentration in cast iron. Compared with conventional mass loss measurements in assessing material degradation in cavitation erosion, surface roughness measurements provide an alternative and convenient method
Corrosion study of metallic biomaterials in simulated body fluid
Full text linkTitanium alloys and stainless steel 316L are still the most widely used biomaterials for implants despite emerging new materials for this application. There is still someambiguity in corrosion behavior of metals in simulated body fluid (SBF). This paper aims at investigating the corrosion behavior of commercially pure titanium (CP-Ti), Ti-6Al-4V and 316LVM stainless steel (316LVM) in SBF (Hank’s solution) at37 ºC using the cyclic polarization test. Corrosion behavior was described in terms of breakdown potential, the potential and rate ofcorrosion, localized corrosion resistance, andbreakdown repassivation. The effects of anodizing on CP-Ti samples and the passivation on the 316LVM were studied in detail. It was shown that CP-Ti exhibited superior corrosion properties compared to Ti-6Al-4V and 316LVM
Processing and properties of silver-metal oxide electrical contact materials
Full text linkThe presented study gives a brief overview of the experimental results of investigations of different production technologies of silver-metal oxide electrical contact materials in relation: processing method - properties. The two most common routes of production, i.e. internal oxidation/ingot metallurgy and powder metallurgy are demonstrated on the example of Ag-CdO and Ag-ZnO materials. For illustration of alternative processing routes that provide higher dispersion of metal-oxide particles in silver matrix more environmentally friendly Ag-SnO2 contact materials are used. Processing of electrical contact materials by mechanical mixing of starting powders in high energy ball mill is presented. The obtained experimental results of application of different methods of introduction of SnO2 nanoparticles in the silver matrix such as conventional powder metallurgy mixing and template method are given and discussed in terms of their influence on microstructure and physical properties (density, hardness and electrical conductivity) of the prepared Ag-SnO2 electrical contact materials
Determination LHP of axisymmetric transient Molybdenum steel-4037H quenched in sea water by developing 1-d mathematical model
Full text linkThe modelling of an axisymmetric industrial quenched molybdenum steel bar AISI-SAE 4037H quenched in sea water based on finite element method has been produced to investigate the impact of process history on metallurgical and material properties. Mathematical modelling of 1-dimensional line (radius) element axisymmetric model has been adopted to predict temperature history and consequently the hardness of the quenched steel bar at any point (node). The lowest hardness point (LHP) is determined. In this paper hardness in specimen points was calculated by the conversion of calculated characteristic cooling time for phase transformation t8/5 to hardness. The model can be employed as a guideline to design cooling approach to achieve desired microstructure and mechanical properties such as hardness. The developed mathematical model was converted to a computer program. This program can be used independently or incorporated into a temperature history calculator to continuously calculate and display temperature history of the industrially quenched steel bar and thereby calculate LHP. The developed program from the mathematical model has been verified and validated by comparing its hardness results with commercial finite element software results. The comparison indicates reliability of the proposed model