Abstract The most important challenges when machining difficult-to-cut alloys used in critical applications consist mainly in increasing tool life as well as improving the component surface integrity. In particular, the nickel based alloys exhibit very low thermal conductivity inducing higher cutting temperature and thereby rapid tool wear. In this context, cryogenic machining is a promising approach that enhances cooling efficiency either when using the liquid nitrogen LN2 or the carbon dioxide LCO2. According to previous works, cryogenic machining has been carried out on several work materials such as titanium alloys and nickel based alloys. Their findings figured out that longer tool life and better surface integrity were obtained when machining titanium alloys, unlike nickel based alloys. In this work, a comparative study has been carried out in order to investigate the cryogenic machining performance during turning operation of Inconel 718 with respect to tool wear behavior and surface integrity of the machined part. In fact, two cryogenic fluids were employed namely LN2 and LCO2 considering as a reference the conventional lubrication. This study illustrates that conventional lubrication and LCO2 cryogenic cooling allowed to obtain similar machining time, tool wear and surface finish. Nevertheless, LN2 cryogenic machining resulted in the lowest tool life as well as the poorest surface finish. Moreover, residual stresses have been measured beneath the machined surfaces when machining using new tools and tools with different levels of tool flank wear. It was observed that compared to conventional lubrication, both cryogenic conditions showed better results with respect to residual stress profiles along the machined surfaces.

中文翻译：

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Inconel 718精车时低温冷却液对刀具磨损和表面完整性的影响比较

摘要 加工用于关键应用的难切削合金时，最重要的挑战主要在于提高刀具寿命以及提高部件表面完整性。特别是，镍基合金的导热性非常低，导致切削温度升高，从而导致刀具磨损迅速。在这种情况下，低温加工是一种很有前途的方法，可以在使用液氮 LN2 或二氧化碳 LCO2 时提高冷却效率。根据以前的工作，低温加工已经对钛合金和镍基合金等几种工件材料进行了加工。他们的研究结果表明，与镍基合金不同，在加工钛合金时可以获得更长的刀具寿命和更好的表面完整性。在这项工作中，为了研究 Inconel 718 车削操作过程中关于刀具磨损行为和加工零件表面完整性的低温加工性能，已经进行了一项比较研究。事实上，考虑到常规润滑作为参考，采用了两种低温流体，即 LN2 和 LCO2。该研究表明，传统润滑和 LCO2 低温冷却可以获得相似的加工时间、刀具磨损和表面光洁度。然而，LN2 低温加工导致刀具寿命最短，表面光洁度最差。此外，在使用新刀具和具有不同刀具后刀面磨损水平的刀具进行加工时，已经测量了加工表面下方的残余应力。据观察，与传统润滑相比，