Abstract
The life of an abrasive wheel, in which cBN and Ni–P are co-deposited on a steel surface by electroless plating, is dependent on the grit adhesion and projection height. In electroless plating, it is difficult for Ni to deposit on ceramic grains. Therefore, surface shape at the grain periphery is not flat but sunken. In this study, with the aim of achieving higher grain support for the abrasive wheel, the surface shape at the grain periphery is improved with the application of ultrasonic vibration. The grain periphery of the specimen obtained with ultrasonic vibration (amplitude 11 μm) revealed an interface with about a 10 μm embossment at the periphery. In addition, the deposition rate with ultrasonic vibration is 1.6 times faster than that without it. This paper also demonstrated that the ideal interface between the cBN grits and Ni–P matrix is expected to have a heaped-up morphology, based on the results of a horizontal pushing-away test by a micro Vickers hardness tester for measuring the adhesive strength of grits. At the same time, the stress distribution around the grits in applying the lateral force to grit was simulated using the finite element method (FEM).
The interfacial morphologies were observed between the cBN grits and Ni–P matrix which were prepared with and without ultrasound. It assumed a flat or slightly sunken shape without ultrasound, whereas it exhibited a heaped-up morphology with ultrasound. The heaped-up height and width depended upon the amplitude, and reached their the maximum at an amplitude of 11 μm. With the best interfacial morphology, the adhesive strength becomes 22% greater than that without ultrasound in the horizontal pushing-away tests. If the grit is pushed to 0.03 N, the maximum interface tensile stress without a heaped-up interface is about 160 MPa in stress analysis by FEM, whereas with such an interface (height: 11 μm; width: 7 μm), it is about 210 MPa, for an increase of about 20%.
