Suppression of diamond tool wear with sub-millisecond oxidation in ultrasonic vibration cutting of steel

Abstract

• Compressed air suppresses diamond wear in ultra-sonic cutting of stainless steel. • Thicker Fe oxide layer on steel surface helps further suppression of tool wear. • High air pressure increases O 2 partial pressure at interface and oxide thickness. • Sufficient oxide layer on fresh-cut steel forms within ultra-sonic cutting interval. • Proposed hypothesis of oxidation replenishes the existing wear suppression theories. Ultrasonic vibration has been applied to suppress the chemical tool wear in ultra-precision diamond cutting of steel and other alloys. The tool wear is found significantly reduced with enriched ambient oxygen concentration. In this study, instead of supplying costly and potentially hazardous high concentration oxygen to the machining zone, a greener alternative, high-pressure air coolant has been applied to enhance the oxygen content at the cutting area. The effect of air-blowing pressure on ultrasonic vibration cutting of stainless steel was investigated, using both polycrystalline and single-crystal diamond tools. It has been found that an increased air blowing pressure and a more closely positioned nozzle not only improve the cutting performance but also reduce tool wear, reflecting consequences from both chemical and fluidic dynamics aspects. A higher air blowing pressure will increase the instantaneous air pressure as well as the density of oxygen molecules around the cutting zone. This increases the passivation speed for the freshly cut steel surface caused by the formation of thin oxide layers. Experimental results have formalized the findings that sub-millisecond oxide formation is the key factor to suppress diamond tool wear.