单颗金刚石磨粒划擦多晶烧结碳化硅陶瓷试验研究

Experimental Research on Single Diamond Grain Scratching Polycrystalline Sintered Silicon Carbide Ceramics

为了研究多晶烧结碳化硅陶瓷材料去除机理,利用自行搭建的单颗金刚石磨粒划擦试验平台划擦无压固相烧结碳化硅陶瓷,在线观察单颗金刚石磨粒划擦多晶烧结碳化硅陶瓷成屑过程,同时采集和分析切削力,然后用光学显微镜观察划痕形貌。试验结果表明,烧结碳化硅陶瓷切屑形态有带状和崩碎状2种,成屑过程可分为带状切屑形成阶段、带状切屑堆积阶段以及切屑崩碎阶段;当切削速度v=0.01mm/s时,切向和法向切削力在t=16s时出现显著的拐点,而v=0.04mm/s时,仅仅法向力出现拐点(t=12.5s),由于在拐点之后切屑呈崩碎状,法向力发生显著的波动;在塑性去除阶段,划痕表面仍存在微小鱼鳞状裂纹,在脆性去除阶段,随着未变形切厚增加,断裂凹坑由间断区域转变成连续区域,直至断裂面扩展至非划痕区域。

To make a further understanding of the materials removal mechanisms of polycrystalline sintered silicon carbide（Si C） ceramics, a single diamond grain scratch platform was built to carry a single diamond grain scratch test on the polycrystalline solid phase sintered silicon carbide ceramics. In the scratching process, the chip formations were observed and the scratching force signals were collected and analyzed, then the scratch morphologies were observed with an optical microscope. The results show that the chip forms of sintered Si C ceramics are classified into continuous chips and collapsing chips, and scratching process has in turn experienced continuous chips formation stage, continuous chips accumulation stage and chips collapsing stage. Besides, when the scratching speed v=0.01 mm/s, there is a significant turning point of tangential and normal scratch force at the time of 16 s. Whereas, at the scratching speed of 0.04 mm/s, the turning point just appears in normal scratching force, and the normal grinding force fluctuates heavily when the scratching time exceeds 12.5 s, which may be due to the collapsing chips formation. What＇s more, even the Si C ceramic materials are removed in ductile mode, there are fishscales cracks appearing on the scratching surface. When polycrystalline Si C ceramics removed in brittle mode, the fractured surfaces transforms from the discontinuous region into the continuous region with the increasing scratching depth. Eventually, the fractured surface extends to the non-scratching area.