A study of the machining of surgical implant material

近年来，为了消除钒对人体的毒害作用，不含钒的钛合金正逐渐取代传统的钛合金如Ti-6Al-4V等作为外科植入物的材料。通常，在包括上述无钒合金在内的钛合金的切削过程中，刀具刃口的温升非常显著，强烈地促进了刀具与被加工材料之间的结合，导致刀具在较短的时间内失效。尽管作为人工髋关节柄的外科植入物在几个规范中都是标准化的，但它们在大小和形式上的差异并不足以适应每一位患者。为了使它们适合任何患者，要求这些植入物可以通过应用MRI或X-射线CT获得的患者的医学图像数据进行机械加工来轻松制造。在上述生物钛合金…的加工中，对提高加工效率进行了尝试采用高温高压直接转化烧结法制备的无粘结剂PcBN刀具，具有较好的高温耐久性。利用该刀具对常规钛合金和两种生物钛合金进行了加工，并对其切削性能进行了评价。加工Ti-6Al-4V合金的无粘结剂PcBN刀具的耐磨性优于硬质合金刀具、PcBN刀具和含Co基粘结剂的聚晶金刚石刀具。Ti-6Al-2Nb-1Ta合金无粘结剂PcBN刀具的后刀面磨损性能与Ti-6Al-4V合金基本相当。另一方面，在加工Ti-15Mo-5Zr-3Al合金时，由于其比Ti-6Al-4V合金具有更高的强度和韧性，导致刀具刃口早期失效。PcBN与钛合金在高温接触下反应生成一定厚度的扩散层，扩散层由钛、硼和铝组成。研究表明，无粘结剂PcBN刀具在高速铣削Ti-15Mo-5Zr-3Al合金时可以提高刀具的使用寿命。较少

Recently, titanium alloys without containing vanadium are going to applied for material of surgical implant in place of conventional type of titanium alloy such as Ti-6Al-4V system, in order to eliminate a toxicological effect of vanadium for human body. In general, the temperature rise in the cutting edge is significant in cutting process of titanium alloys including above mentioned vanadium-free alloys, promoted strongly the adhesion between tool and work materials, resulting in tool failure within relatively short duration. Although surgical implants as a stem of an artificial hip joint are standardized in several specifications, their variations in size and form are not enough to fit every patient. To make them fit to any patients, it is required that these implants can be manufactured easily by machining with application of the patient's medical image data obtained by MRI or X-ray CT. Improvement of processing efficiency was tried in machining of above described bio-titanium alloy … More s. A binder-less PcBN tool which is prepared through the direct conversion sintering of hBN under both high pressure and temperature, exhibits an improved high temperature durability. The tool was applied for machining of the conventional Ti-6Al-4V alloy and two types of bio-titanium alloys, then cutting performance are evaluated. The wear resistance of a binder-less PcBN tool for machining Ti-6Al-4V alloy was superior to those of the tools made of cemented carbide, PcBN and polycrystalline diamond with Co-based binder. The performance of the binder-less PcBN tool for Ti-6Al-2Nb-1Ta alloy was almost equivalent to that for the Ti-6Al-4V alloy in flank wear characteristics. On the other hand, for machining of the Ti-15Mo-5Zr-3Al alloy, the cutting edge failed in earlier stage due to its higher strength and toughness than Ti-6Al-4V alloy. The reaction between PcBN and titanium alloy under a high thermal contact produced the diffusion layer with certain thickness which consisted of Ti, B and Al. It was clarified that the binder-less PcBN tool could improve tool life in high-speed milling of the Ti-15Mo-5Zr-3Al alloy. Less