Dissertation > Excellent graduate degree dissertation topics show

Correlation between Process Variables and the Coating Feature in Wire Explosion Spraying

Author: YangQi
Tutor: ZhuLiang
School: Lanzhou University of Technology
Course: Materials Processing Engineering
Keywords: Electrical explosion of wire segment Electric spray Spray distance Energy density Vapor deposition Gas discharge
CLC: TG174.44
Type: Master's thesis
Year: 2009
Downloads: 48
Quote: 0
Read: Download Dissertation

Abstract

Electrical explosion spraying technique is a pulsed high voltage is applied to the metal filamentous spraying material, so that explosion, its explosive product at high speed under the explosive impact force to the surrounding sputtering, in conjunction with the surface of the base material forming the surface of the coating technology. The electrical explosion spraying can use a refractory metal such as tungsten, molybdenum, a spray coating material, particularly suitable for spraying the inner surface of the workpiece. The electrical explosion spraying process, applying a discharge voltage on the metal wire, the spray distance between the metal wire and the substrate, the geometric dimensions of the filamentous spraying material, spraying substrate surface properties, and other factors, will be the quality of the coating and bonding strength impact. For the system to recognize the relationships between them, the use of the wire segments of the wire segment in the high voltage electric field electrical explosion device under different discharge voltage and spraying distance, a series of wire segments electrical explosion Spray Test, the combination of electrical explosion coating microscopic analysis, the understanding of the relationship between the electrical explosion spraying process parameters and coating properties. By changing the length of the wire and electrode voltage, a series of wire segments electrical explosion spraying test, the electrical explosion coatings prepared by different distance away from the center of the electrical explosion. Recognize when about 3 ~ 5mm air gap, the electrical explosion spraying effect, the length of the wire in the specific field distance can be a reasonable choice. The change in the length of the wire on the area of ??adhesion of the coating is also affected, to increase farm spacing decreases with the length of the wire at the same time, spraying the coating on the substrate. Change voltage, spray distance, and other parameters, to obtain the four different types of coatings, sprayed layer of molten particles, the solid particle accumulation layer, vapor deposition layer, the vapor accumulation layer. Wherein high bonding strength of the sprayed layer and the vapor-deposited layer of molten particles, and industrial application value. Resultant coating electrical explosion spraying experiment, the study found that the explosion products with the input to the increase of the discharge voltage of the metal wire, by the molten particles coating changes to the vapor deposition coating. The spraying distance is the critical process parameters determine the properties of the coating, the formation of vapor deposition coating the required spraying distance is very short, and the molten particles sprayed layer can be obtained in the larger range of the spray distance. Found that by changing the wire diameter, the quadratic growth, energy per unit volume becomes small with the increase in diameter of the wire, the wire volume, quality will occur. So that the granularity of the resulting coating from 1μm to 5 μm is increasing, the surface morphology of the coating is also shift by the aggregates of the fine particles - Dense - loose several forms. Sectional morphologies spray sample observations using scanning electron microscopy (SEM) observations coating and the substrate surface morphology of the junction, and the combination of the coating and substrate. Porosity from the coating, the bonding the particle deformation stacking three study the properties of the coating. The powder particles in the lower energy when the general form of droplets sprayed into the surface of the substrate to form a coating; higher energy when the electric explosion of fine particles will be deposited onto the surface of the substrate to form a coating. Interface tightly formed simultaneously, the combination of high strength, low porosity. Due to stacking unevenness, there are the defects of 1μm to 2μm. By the energy density in the four different types of coating were calculated and analyzed, summarized the approximate energy density range of the formation of various coatings. Explosion products with the input to the increase in the energy density of the metal wire, the molten particles share gradually reduced, while the gaseous component is gradually increased. While recognizing the the electrical explosion spraying process, for the specific spray material is applied to the size of the electrical energy in the unit volume of the discharge of the spray material directly determines the particle size, velocity and temperature of explosions. Electrical explosion process the voltage and current waveforms are collected with a Rogowski coil. The instantaneous energy, the change of the voltage, current discharge process, the length of the discharge time, and in this process have a certain understanding by analyzing waveforms.

Related Dissertations

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology > Metal complex layer of protection
© 2012 www.DissertationTopic.Net Mobile