Study On The Machining Technology Of Non-conventional Holes And Pockets For Ceramic Matrix Composites

Ceramic matrix composites has excellent high temperature performance. And due to the enhancements of the reinforced fibers, CMC is an ideal choice as heat protection and high-temperature structural materials with high structural strength and toughness. Quartz fiber reinforced ceramic matrix composites and C/SiC ceramic matrix composites are representative and widely used. Ceramic matrix composites’Advantages in high-strength, lightweight and high temperature resistance are fully reflected in manufacturing areas such as aerospace engines, missile radomes, aircraft thermal protection and high-performance brakes. However, in the manufacture of these components, the high hardness, wear resistance and other characteristics bring difficult for machining and cause manufacturing defects easily. Besides, because of the special application scenarios, the structures generally have unconventional processing feature. For example the aero-engines contain Non-rotating pockets inside, easily lead processing interference. Flat-bottomed blind holes are required to be machined for radome assembly. These issues have hindered the development and application of ceramic matrix composites.In this paper, in different parts manufacturing, the study was carried out on blind hole helical milling of quartz fiber reinforced ceramic matrix composites using diamond tool, and deep-cavity pockets machining technology for C/SiC ceramic matrix composites. Main contents and results achieved are as follows:(1) Analyzing characteristics of quartz ceramic matrix composites, the difficulties to guarantee machining quality and tool life in blind hole drilling process are summarized. Helical milling using diamond tool is selected for the blind hole processing. And material removal mechanism was analyzed. The experimental results showed that:The process method can effectively improve the processing chip discharge conditions, reduce the cutting heat, improve processing quality.(2) Through the blind holes helical milling processing of quartz fiber reinforced ceramic matrix composites, the processing parameters were tested for comparison. With analysis of the main factors affecting the helical milling force and hole-quality, comparative test was designed to analyze processing parameters’ impact on the cutting temperature, cutting forces and made the hole quality. And the reasonable helical milling blind hole machining process specifications for quartz ceramic matrix composites are determined.(3) Processing experiments for C/SiC ceramic matrix composites are proceed to compare cutting force variation processing quality under different process parameters. Based on the test results, reasonable range of parameters are determined according to the processing requirements. And design basis are provided for deep-cavity pockets processing equipment. Meanwhile, special tools and processing method are design based on the characteristics of deep-cavity structure.(4) According to the structure and geometry of deep-cavity pocket, the equipment for C/SiC ceramic matrix composite deep-cavity pocket processing is developed. Cutting tools and process flow were also designed based on the characteristics of deep-cavity pocket structure. And Different tool path plan for deep-cavity pockets machining were compared in the impacts on processing efficiency and cutting stability, which provides a complete set of technical solutions for the machining of the subsequent product.