Abstract
The use of ionized gaseous medium (IGM) to prepare a hard alloy material surface by grinding and its effect on the coating quality was investigated. During grinding, IGM was fed to the cutting area by different methods namely: clockwise (longitudinal), anticlockwise (opposed) and transverse (Cross) feeding, respectively. Thereafter, the samples were coated with a titanium nitride on a modern vacuum, ionizing apparatus HHB-6.6-u1 by physical vapour deposition (PVD) method, known as condensation and ionized bombardment (CIB). The analysis of the results and tests carried out revealed that IGM improves the quality of coating, especially when IGM was fed anticlockwise and when the corona discharged current (tk) was equal to 50 mA. The lowest component forces were also gotten by anticlockwise feeding for example, the component forces (Py Pz) were 2 times and 1.5 times lower compared to longitudinal and cross feeding of IGM, respectively. The micro hardness of inserts ground with IGM was about 10% higher than those ground with other types of fluids. The micro photograph of inserts structure revealed a distinct and better coated layer for the inserts surfaces prepared prior to coating with IGM. Whereas inserts prepared with compressed air and without cutting fluids showed very blur and indistinct coated layer. It was established that inserts whose surfaces were prepared with IGM and then coated with the titanium nitride (TiN) showed tool-life of about 4 times greater than others. Key words: Ionized gaseous medium, hand alloy tool inserts, coating, condensation and ionized bombardment, titanium nitride.
Highlights
The high rate of cutting tools wear during machining
Samples A1 showed a very high coating quality and there was no sign of exfoliation or formation of micro cracks around the indenter’s imprint
Samples A2 have good coating quality because there was no observation of coating exfoliation, but there were very slight traces of micro cracks
Summary
The high rate of cutting tools wear during machining (that is, during metal cutting operations, especially during rough machining). It has led to a constant high demand for tools with high wear resistance. This is more pronounced in railway industries (companies) where large quantity of metal layers is removed from the rail wheel-pairs surface everyday. There are many ways of increasing the cutting tool war-resistance (tool life). Some of these ways are the use of cutting fluids, coating the tools surfaces, optimizing the methods of re-sharpening the tool cutting edge(s), etc. Coating enhances the tool life more than any of the other method (Anikeev et al, 1980)
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