Microstructure and Tribological Properties of Copper-Based Rare Earth Luminescent Composites Prepared by SPS

The friction and wear of machinery and equipment is wide spread, and the wear loss is the main cause of mechanical equipment damage and mechanical failure. Using various wear monitoring technologies to monitor the wear status of key components of machinery and equipment on a regular basis or in real time can ensure safe and reliable operation of the equipment, and avoid the expected downtime for maintenance or even economic losses caused by major safety accidents. At present, wear detection technology mainly includes vibration noise monitoring, oil monitoring, luminescent coating monitoring technology, etc. Among them, luminescent coating wear monitoring technology has a simple detection method, intuitive and clear detection results, and a wide range of application and has a broad development space. In this paper, copper-based rare-earth luminescent composites were prepared using (Ca, Sr)AlSiN₃:Eu²⁺ phosphor and copper powder as raw materials by the discharge plasma sintering (SPS) process. The effects of (Ca, Sr)AlSiN₃:Eu²⁺ content on the microstructure, phase structure, luminescence properties, micro and nano mechanical properties and tribological behavior of the copper-based composites were investigated by scanning electron microscopy (SEM), X-ray diffractometer (XRD), fluorescence microscopy, microhardness tester, nanoindentation tester and micro-motion friction and wear tester. The results showed that the phosphor was very stable during the sintering process, which could hinder the formation of copper grain sintering necks and limit the grain boundary migration of copper grains, leading to the continuous refinement of the grain size of copper-based rare-earth luminescent composites with the increase of phosphor content, which caused the increase of nanomechanical and elastic modulus of the composite matrix phase. At the same time, the hard phosphor particles inhibit the material's adhesive wear and reduce the friction coefficient while improving the composite's resistance to plastic deformation and abrasive grain wear. The above two effects resulted in significant improvements in the microhardness and tribological properties of the copper-based rare-earth luminescent composites. The wear resistance of the composites increased with the increase of (Ca, Sr)AlSiN₃:Eu²⁺ content and then decreased, which was mainly due to the poor bonding between phosphor particles and copper matrix phase, and the increase of phosphor content led to the increase of defects such as pores and cracks in the material, causing the decrease of microhardness, and it was easy to induce (Ca, Sr)AlSiN₃:Eu²⁺ particles to fall off and became abrasive particles during the sliding friction process, which weakened the wear resistance of the composites. Thus weakening the wear resistance of the composites. In addition, the phosphor particles inside the composite remain effective during the sintering process, and can emit red fluorescence under the excitation of additional light, which has good luminescence performance and provides support for its use as a luminescent wear monitoring coating.