SEM Observations on Wear Mechanism of TiN–Coated HSS Twist Drills When Drilling Mild Steel

Abstract

Dalam kajian ini, haus mekanikal Keluli Laju Tinggi (KLT) telah dikaji dengan menjalankan ujian prestasi gerudi ke atas bahan kerja diperbuat daripada keluli lembut. Salutan TiN ke atas HSS twist drills diperolehi dengan menggunakan kaedah bertindak balas frekuensi radio pemercitan magnetron yang mana dibangunkan secara dalaman. Ujian prestasi gerudi dijalankan pada kelajuan pusingan 1,600 psm, kadar suapan 20 mm/minit dengan kedalaman penggerudian 25 mm. Perubahan morfologi permukaan haus diperhatikan dengan menggunakan kaedah Kemikroskopan Imbasan Elektron (KEI). Keputusan morfologi menunjukkan mekanisme rekatan dan haba beroperasi semasa proses penggerudian. Kertas kerja ini juga akan membincangkan secara mendalam proses penjanaan mekanisme haus rekatan dan haba semasa penggerudian gerudi piuhan ke atas plat keluli lembut. Keputusan ujian prestasi gerudi menunjukkan salutan TiN terendap ke atas KLT gerudi piuhan telah meningkatkan umur gerudi melebihi dua kali ganda jika dibandingkan dengan gerudi yang tidak bersalut. Kata kunci: Gerudi KLT, KEI, mekanisme haus, rekatan, haba In this study, High Speed Steel (HSS) twist drills were investigated for mechanical wear by performing drilling test on the work piece of mild steel plate. TiN coatings onto the HSS twist drills were achieved by employing reactive radio frequency (r.f) magnetron sputtering technique, which was developed in–house. The drilling performance tests were set at a rotation speed of 1,600 rpm, feed rate of 20 mm/min, and depth of cut of 25 mm. The morphological changes of the wear surface were observed using Scanning Electron Microscopy (SEM). Results of morphological examination showed that the failure mechanisms in operation during drilling were found to be adhesive and thermal wear mechanism. This paper will also discuss explicitly the processes of adhesive and thermal wear mechanism generated during drilling of twist drill on mild steel plate. Results of drilling performance test showed that the TiN coating deposited on the HSS twist drill had improved drill life by more than 2 times as compared with uncoated drill. Key words: HSS drill, SEM, wear mechanism, adhesive, thermal