TiB_2增强Al_2O_3陶瓷刀具高速干切削摩擦磨损性能

Friction and Wear Behavior of TiB_2 Reinforced Al_2O_3 Ceramic Cutting Tool in Dry Cutting of Hardened Steel at High Speed

采用TiB2增强Al2O3陶瓷刀具对淬硬钢进行高速干切削试验,利用切削高温作用下的摩擦化学反应,在刀具表面原位生成具有润滑作用的反应膜,从而实现Al2O3/TiB2陶瓷刀具的自润滑.结果表明:低速干切削时,Al2O3/TiB2陶瓷刀具的磨损机制主要表现为粘着磨损和磨料磨损;而在高速干切削时,刀具的磨损机制主要表现为氧化磨损,刀具表面经由氧化反应生成具有润滑作用的反应膜而起到固体润滑作用,从而使刀具的耐磨性能提高,随着TiB2含量和切削速度的增加,反应膜的减摩抗磨作用增强;而在切削区通入氮气时,由于刀具表面氧化膜形成受阻,刀具的抗磨能力有所降低.

Dry cutting tests at high speed were carried out with respect to hardened steel and TiB2 reinforced Al2O3 ceramic cutting tools. Thus the friction and wear behavior of the tool was reduced by in-situ forming an oxide film on the tool rake face, making use of the tribochemical reaction at high cutting temperature. The effect of the tool composition on the friction and wear behavior was investigated, and the morphologies of the rake face and the rear face of the tool in cutting the steel (AISI-1045) in air and nitrogen were observed on a scanning electron microscope. It was found that the Al2O3/TiB2 tool was dominated by adhesive wear and abrasive wear in low speed dry cutting; while in high speed dry cutting, the tool was characterized by oxidation wear. An oxide layer of TiO2 was formed by way of the oxidation of the reinforcing agent TiB2 at a very much high cutting temperature, which contributed to greatly reducing the friction coefficient and increasing the antiwear life of the tool. Such a friction-reducing and antiwear behavior of the oxide layer was enhanced with the increase of TiB2 content in the tool composite. However, the tool showed a relatively poorer wear resistance in N2 than in air, because N2 acted to retard the oxidation of the TiB2 and the formation of the oxide layer on the tool rake face.