使用超音速等离子喷涂设备在1045钢基体上制备了铁基合金涂层。以球盘式接触疲劳试验机为平台,研究了涂层接触疲劳损伤过程中声发射特征参数的变化规律,并分析了涂层的接触疲劳损伤机理。结果表明,在转速为2500r/min和应力水平为1.58GPa实验条件下,点蚀是涂层的主要失效形式,表现为在涂层磨痕轨迹范围内出现大量的点蚀坑,点蚀坑深度为20～30μm。涂层表面粗糙的微凸体与轴承球滚压接触产生黏着磨损,以及涂层、磨粒、滚动轴承三者形成三体磨料磨损是点蚀失效产生的主要原因。声发射幅值、有效值(Root Mean Square,RMS)、能量、计数和平均频率对涂层表面粗糙微凸体去除、弹塑性变形、裂纹萌生、裂纹稳定扩展和失稳扩展过程比较敏感,并且在不同的疲劳损伤阶段具有不同的信号反馈特点。
Based on the foreign remanufacturing mode,which relies mainly on Part-Replacing Repair Method and Size-Changing Repair Method,China has explored and practiced the new remanufacturing mode,which relies mainly on Surface Repair and Performance Improving Method.The aim of remanufacturing forming is to renew rapidly the original size of the waste components rapidly,and then improve their service performance.The advanced surface engineering technology,especially the high density heat source surface forming technology,is the important technique to carry out rapid forming.Based on the arc heat source,plasma heat source and laser heat source,three kinds of high density heat source remanufacturing forming technologies,such as high speed arc spraying forming technology,micro-arc plasma forming technology,and laser cladding forming technology,have been developed.The benefits of remanufacturing forming based on advanced surface engineering technologies are great.
The defects of remanufacturing coatings,such as micro-cracks,micro-pores,oxide inclusion,and fatigue cracks producing in the service process have great influence on the qualities and lives of remanufacturing coatings.This paper summarizes several methods used for detecting coating defects,including ray method,ultrasonic method,eddy method,magnetic memory method,acoustic emission method.The advantages and limitations of the above methods are also discussed.The detection results by ray method are visualized,and it is easy to achieve qualitative,quantitative and locating detection,but this method has incipient fault and low detecting sensitivity.Ultrasonic detection can exactly locate defects,and it is sensitive to plane defects,but the detection has dead zones,and it is inconvenient to perform qualitative and quantitative measurement.Eddy method detects fast,but it only can detect conductive materials,and is difficult to achieve qualitative,quantitative and locating detection.Magnetic memory method is sensitive to ferromagnetic materials,but it can not detect nonferromagnetic materials and is difficult to attain quantitative measurement.Acoustic emission method has an extensive detection range and high sensitivity,but it has big noise interference,and is hard to achieve qualitative detection.In conclusion,it describes the application prospect of each method for detecting coating.
