# Cutting Performance and Wear/Damage Characteristics of PCBN Tool in Hard Milling
## 1 Introduction  
PCBN is a cutting tool material most widely used in the machining of hardened steel due to its higher hardness, strength, thermal and chemical stability, and thermal conductivity, and lower friction coefficient than other tool materials at high temperature [1; 2; 3]. Cutting performance and wear characteristics of PCBN tools were extensively studied in the hardened-steel cutting process. During continuous and intermittent turning, the cutting performance and wear mechanism of PCBN tools were extensively studied. The cutting performance of PCBN tools with different CBN (Cubic Boron Nitride) content was investigated [4]. It was found that PCBN tools with low CBN content had better cutting performance than that of PCBN with high CBN content. The influence of chamfering angle on the cutting performance of PCBN tools was investigated [5; 6; 7]. It was found that the chamfering angle could effectively reduce cutting force, flank wear, and white layer thickness. [PERSON] et al. [8] investigated the cutting performance of PCBN tools with variable micro-geometry in hard turning AISI4340 steel. It was found that the variable micro-geometry PCBN tool could effectively reduce cutting heat, plastic deformation of workpiece, and tool wear. The effect of the microstructure of hardened steel on the PCBN tool wear was investigated [9; 10]. In addition, the effects of new tool materials [11] and high-pressure cooling technology [12] on the cutting performance of PCBN tools were studied. The main wear mechanism of PCBN tools in continuous and intermittent cutting of hardened steel (1117 steel, HRC62+1) was abrasive wear [13]. The main wear mechanism of PCBN tools in intermittent turning of bearing steel (AISIE-52100, HRC60) was abrasive wear and adhesion wear [14]. The main wear mechanism of PCBN tools in continuous and intermittent cuttingof hardened steel (AISI 4340, HRC56) was abrasive wear [15]. Under high-pressure cooling conditions, PCBN inserts primarily sustain adhesive wear, groove wear, and abrasive wear on the flank face when cutting GH4169 [12]. [PERSON] et al. [16] studied the effect of quenching hardness on the wear properties of PCBN tools for dry hard turning. The results showed that the wear mechanism of tool flank was abrasive wear in the cases of 40-55 \(\pm\) 1 HRC and abrasive and delamination wear in the case of 60 \(\pm\) 1 HRC. The wear mechanism of PCBN tools was abrasive wear in the machining of high-chromium white cast iron [17; 18]. There were a few studies on the cutting performance and wear mechanism of PCBN tools in the milling process. [PERSON] et al. [19] carried out an experimental study on end milling of DileVAR hardened steel (50 HRC) with PCBN tools. The results indicated that the PCBN tool gave excellent performance in terms of tool life and surface finish in comparison with carbide-coated tools. [PERSON] et al. [20] investigated the life of PCBN tools in milling die steel. The results showed that the tool life was affected by the cutting speed. [PERSON] et al. [21] studied the cutting force, cutting temperature, tool wear, and surface roughness of PCBN tools with different CBN content in hard milling hardened steel. It was found that PCBN tools with high CBN content had higher cutting performance. [PERSON] et al. [22] investigated the wear properties of PCBN ball-end milling cutters with different CBN content in high-speed milling hardened AISI H13 die steel. It was found that the main wear forms of PCBN ball-end milling cutters with 90% CBN and 65% CBN were flank wear and chipping, respectively. [PERSON] et al. [23] proposed a three-dimensional wear parameter method based on a focal-length change microscope to evaluate PCBN tool wear and wear mechanism. It was found that there was a nonlinear relationship between abrasive wear, adhesive wear, and diffusion wear, and material hardness. Its calculated results were nearly the same as those given by [PERSON] et al. [24]. [PERSON] et al. [25] investigated the wear properties of PCBN tool with high CBN content in milling hardened steel.