Papers by Author: Jiu Hua Xu

Abstract: Ti-6Al-4V alloy was hydrogenated at 800°C by thermohydrogen treatment technology. Sliding friction and wear tests were carried out in a special tribometer assembled on CA6140 turning lathe to investigate the friction and wear morphology between hydrogenated titanium alloys and WC-Co cemented carbides. The morphological analyses of the worn surface were made by scanning electron microscope. It was found that the friction coefficient and the friction area temperature of the pair both firstly decreased and then increased with the increase of hydrogen content, and the friction coefficient decreased and the friction area temperature increased with increasing sliding speed. The main wear morphologies of the unhydrogenated alloys were serious plastic deformation, ploughing, adhesion tearing pit and fatigue microcrack, but the main wear morphologies of the hydrogenated alloys were boundary of plastic extension, slight scratch and slight adhesion tearing. Besides, the main wear morphology of the tool corresponding to unhydrogenated alloys was massive spalling, but the main wear morphology of the tool corresponding to the titanium alloy with 0.29% hydrogen content was punctate spalling.

Abstract: This study aims to investigate the wear of coated end mills when milling Carbon fiber reinforced polymer (CFRP) composites. Four different types of end mills are used in the milling experiments to identify the influence of tool geometry and material on tool wear. Cutting forces and wear mechanisms of coated mills are also discussed. Through the contrast experiment, diamond coated multitooth router shows the best performance with the smallest cutting force and the least wear extent under the same cutting parameter. The major failure mechanisms of coated tools are breakthrough of coating, coating flaking and abrasive wear of substrate.

Abstract: Monolayer brazed diamond tools, which are high bonding strength at the interface between brazing alloy and grits, are becoming the active field in which improvements in processing and advanced products can be anticipated. Some researchers proposed brazing diamond methods with Ni-Cr and Ag-Cu-Ti alloy, but there is a shortage of the comparative study of the characteristics of the brazed diamond tools fabricated with the different brazing alloy. In this paper, machining performance experiments have been carried out, including contrast tests about tool life and machining efficiency for thin-walled monolayer brazed diamond core drills fabricated with Ni-Cr and Ag-Cu-Ti alloy. The results show that the Ag-Cu-Ti alloy can improve the machining performance. Wear mechanism of diamond grits was studied in those drilling processes. The results show that the low ratio of grit breakdown of the core drill using Ag-Cu-Ti alloy is the key factor of its longer life. Furthermore, based on the experimental results, the areas of the grits wear flat increase the feed force, and decrease the machining efficiency.