锆基非晶合金冰冻切削加工特征及其无晶化加工工艺研究

Freezing Cutting Characteristics and Non-crystallized Processing Technology of Zr-based Bulk Metallic Glass

锆基非晶合金切削过程中的高切削热会导致工件表面晶化,使非晶合金优异性能丧失。提出将冰冻盘夹具用于非晶合金铣削加工,提升切削散热能力,实现非晶合金冰冻切削加工。研究了非晶合金冰冻铣削过程中的燃烧发光特征及其影响因素;分析了冰冻切削工艺(切削速度、进给量和刀具涂层材料)对非晶切削力的影响规律;优化了适用于非晶合金无晶化加工的冰冻切削工艺参数,并揭示了涂层刀具的磨损失效形式。结果表明,锆基非晶合金切屑燃烧发光是导致非晶冰冻切削加工表面晶化和表面粗糙度增大的根本原因;引起切屑燃烧发光的主要因素包括高切削速度、小进给量以及因切削长度增加导致的刀具磨损积累,改变刀具涂层不会导致切屑燃烧发光;切削力主要受切削速度影响,对进给量不敏感;TiSiN、TiAlN、CrSiN和AlCrN四种涂层刀具的失效形式均为后刀面黏结磨损、前刀面涂层剥落以及刀尖崩缺;CrSiN涂层具有最佳的抗黏结磨损能力,可获得最小切削力和最低表面粗糙度。通过优化冰冻切削工艺,可以实现锆基非晶合金的高速铣削加工,同时避免切屑燃烧发光,获得高质量的无晶化加工表面。

The high cutting heat in machining of Zr-based bulk metallic glass(Zr-based BMG) can trigger the crystallization of workpiece materials, which in turn leads to the loss of excellent properties of the BMG. The use of icing clamp to fix workpiece in order to realize the freezing machining of BMG is proposed. The light emission features and associated influencing factors are studied. The effects of freezing cutting parameters, including cutting speeds, feed rates and tool coatings on BMG cutting force are analysed. The high-efficient, precise and non-crystallized processing technology in freezing cutting, is optimized. Also, the wear form for coated tools are revealed. The results show that the light emission in BMG freezing cutting is the primary causes for the machined surface crystallization and high surface roughness. The main factors that cause this phenomenon included high cutting speed, small feed rate and tool wear accumulation with increased cutting length. No light emission is observed when changing tool coatings. Cutting force was mainly affected by cutting speed, but it was not sensitive to feed rate. The failure modes for the four coated tools, TiSiN, TiAlN, CrSiN and AlCrN, are the adhesive wear of flank face, the coating peeling off of rake face and the tool tip chipping. Among them, the CrSiN coating had the best adhesive wear resistance, and can get the minimum cutting force and the best surface quality. By optimizing freezing cutting process, the high-speed milling of Zr-based BMG can be achieved, while avoiding the light emission, and getting high-quality non-crystallized machined surface.