Wear of Diamond-impregnated Bit in Drilling Engineering Ceramic
This paper describes experimental results using a scanning electron microscope (SEM) to observe the face of diamond-impregnated bit after its drilling engineering ceramic. Wear patterns and mechanisms were analyzed. The results show that several diamond wear patterns are found in the bit face including complete crystal shape, micro fragmentation, extensive fragmentation, whole fragmentation, wearing flat and particle shattered, bond abrasion mainly is in the form of shifting sand pattern, alternating thermal stress and mechanical stress are the main reasons which lead to the diamond wear, extrusion force, friction as well as abrasive debris erosion result in the shifting sand pattern of the bond.
Performances of Diamond Impregnated Bit in Hole Drilling of Engineering Ceramics
According to the mechanical characteristics of engineering ceramics,the special diamond impregnated bits are developed for hole drilling.The cutting performances of the bits are analyzed from the following aspects,such as bit wear,working life,machining efficiency and machining quality.The results show that: the whole bit wear process can be divided into three phases;the regularity of the machining time per hole with the number of holes machined is close to a periodic variation;higher machining efficiency or working life can be obtained when the drilling pressure and the wall thickness of the bit are advisable.Aiming at the drilling defects in engineering ceramics,drilling with compressive pre-stress is proposed.Experimental results show that the bit is suitable for the drilling of engineering ceramics.Research achievements provide technical bases for the application of diamond impregnated bits in hole drilling of engineering ceramics.
A New Grinding Method for Ceramics Using a Biaxially Vibrated Nonrotational Ultrasonic Tool
Summary A new method for grinding ceramics and hard materials by using a non-rotational tool has been developed. In the method a fixed abrasive type grinding tool is vibrated by a complex ultrasonic transducer longitudinally and torsionally at the same time. Experiments showed that the complex ultrasonic vibration keeps grinding force low and stable for a long time in grinding hard ceramics even without rotating the tool. When a diamond grinding tool with a square or triangular bottom is used, this method has a great effect on producing cavities with sharp inner corners of almost zero radius on various hard-to-machine materials.