Resurfacing the exhaust valve by plasma spraying versus electric arc and gas flame methods

In modern conditions of economic instability in various sectors of industry for the national economic complex, it is important to improve the technology for repairing parts of power units, while the development of modern technological methods for restoring the contact surfaces of parts should be carried out in the conditions of enterprises and be accessible. The article compares the most common methods of surface parts restoration, such as flame, plasma spraying and electric arc surfacing. Studied experience of various specialists working in this direction made it possible to implement these reduction methods using a charge based on a mineral tungsten-containing concentrate, boron and carbon. The process of alloying the resulting coatings was investigated, where tungsten is in the form of tungsten trioxide (WO3) and calcium tungstate (CaWO4). A comparative analysis of the methods for restoring the surface of the exhaust valve cone of the D49 diesel engine has been carried out. The article presents results of microand macroanalysis of the structures of the obtained coatings and the base metal of the restored part, the results of the analysis of the chemical composition, the evaluation of the microhardness and adhesive strength of the adhesion of the obtained coatings to the surface of the base metal. Authors substantiated the prospect of applying the methods of gas-thermal restoration of the surface of parts in relation to the method of electric arc surfacing. Subsequent studies will focus on the installation of remanufactured parts in the internal combustion engine of the locomotive, their operation in real conditions, and the assessment of reliability and durability. Research in this direction will improve the quality indicators of the restored surfaces of power unit parts of rolling stock.

Burn Baby Burn: Igniting a Plasma, and Properties

The purpose of the Flame Plasma experiment is to measure the electron density in an intensified propane flame. This is done by sweeping a Langmuir probe through the flame, and measuring the resulting current and voltage through it. The properties of the Langmuir probe and flame plasma are further analyzed. In the Flame Plasma experiment, a flame will be created with a lab-grade propane burner (this may need to be purchased, preferably one with a large diameter). The flame will only contain partially-ionized plasma, which means not all atoms are going to be stripped of their electrons. To create more uniformly-ionized plasma, a more intensified flame must be created. This can be done by “seeding” and intensifying the flame with “sodium” and “potassium” particles. This more uniformly-ionized plasma will contain a higher electron density. This is an important pre-requisite for the Langmuir probe for it to work well, and not acquire error-like readings and charts.

EFFECTS OF SURFACE TREATMENTS AND SILICA SIZE ON MECHANICAL PROPERTIES OF SILICA-REINFORCED ELASTOMERIC COMPOSITES

ABSTRACT The effect of surface treatments with atmospheric pressure flame plasma (APFP) and epoxy silane (ES) was studied experimentally to improve the mechanical properties of silica- (volume 40% and mean diameters of 2.2, 12.4, 26.6, and 110 μm) reinforced elastomeric composites. The tensile strength (TS) of the composites increased significantly with decreasing mean diameter. When the diameter was 2.2 μm, the TS of the composite was approximately 1.4 times higher than that of the matrix (2.52 MPa). In addition, the TS of the silica-reinforced composites treated with APFP and ES was increased by 8.8 to 13.3% and 9.9 to 12.5%, respectively, compared with that of the matrix. A larger particle size generally resulted in better surface treatment effects. When the diameter was 26.6 μm, the tensile modulus (TM) of the composite was increased approximately twofold compared with the matrix (0.88 MPa), and the TM of the silica-reinforced composites treated with APFP and ES was increased by 15.6 to 22.8% and 21.1 to 25.8%, respectively, compared with the matrix. Therefore, the importance of surface treatments increases with increasing filler particle size. A conventional silane-coupling agent treatment has few disadvantages, such as the use of organic solvents. Nevertheless, the APFP treatment is a fast, economic, and eco-friendly method for improving the mechanical properties.