Accelerated electrospark deposition and the wear behavior of coatings
- PDF / 1,596,481 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 74 Downloads / 209 Views
9
International
Accelerated Electrospark Deposition and the Wear Behavior of Coatings P.-Z. Wang,* G.-S. Pan, Y. Zhou, J..X. Ou, and H.-S. Shao Electrospark deposition (ESD) is a coating process that is featured by low heat input to the substrate. Low coating efficiency and other limitations influence its wider application. The present paper introduces newly designed ESD equipment, by which a higher coating rate can be reached. The relationship among coating thickness, surface roughness, and process parameters such as pulse energy, pulse frequency, and deposition time are presented. Electrospark deposition coating by the new equipment on AISI 1045 steel (with WC-8% Co as electrode) increases the wear resistance by 5 to 8 times. The micromechanism is investigated by scanning electron microscopy observation.
Keywords
coating, electrospark deposition, equipment, wear behavior
1. Introduction Electrospark deposition (ESD) is a coating process in which short-duration, high-current electrical pulses are supplied between the electrode (anode) and the workpiece (cathode). A coating is deposited onto the surface of workpiece by pulse-arc microwelding. Since its invention, ESD has been used mainly in two kinds of applications. One is to enhance the performance of electrical contact points such as those used in relays (Ref 1), while the more common applic.ation is to increase service life of many parts subjected to wear, such as lathe tools, drills, milling cutters, hacksaw blades, camshafts, turbine blades, and so forth (Ref 2-6). Electrospark deposition coating possesses some unique advantages. The principal one is that the coatings are metallurgically bonded to their substrate with such low total heat input that the bulk substrate material remains at or near ambient temperature (Ref 2). The short duration of the electrical pulse results in an extremely rapid solidification of the deposited material and produces an exceptionally finegrained coating that approaches an amorphous structure. In most cases the ESD equipment is simple, cheap, portable, and easy to operate for any surface, especially those that are irregular and complex. There are also some limitations, such as the low coating efficiency, stress relief cracking in coating, both workpiece and electrode must be electrically conductive, and so forth. Several factors influence the coating efficiency, such as the properties of the electrode (melting points, heat capacities), environment (gas, oil), and materials transfer mode (molten globular mass transfer or spray transfer) (Ref 7). However, the charge-discharge frequency is the most important factor. The two typical kinds of conventional ESD equipment are shown in Fig. 1. For P.-Z. Wang, G.-S. Pan, Y. Zhou, J.-X. Qu, and H.-S. Shao, Beijing Graduate School, China University of Mining & Technology, Beijing 100083, P.R. China. *Correspondence address: Dr. P.-Z. Wang, Department of Materials Science, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom. 780---Volume 6(6) December 1997
the v
Data Loading...
