Abstract: SiCp/Al composites with high volume fraction and large particles are very difficult to machine. In this present study, high-speed milling experiments were carried out on the SiCp/Al composites by the three factors-levels orthogonal experiment method, and multiple linear regression analysis was employed to establish milling force model. The results show that the milling forces decrease with the increasing of the milling speed or increase with the increasing of the feed rate and depth of milling. The influence of milling depth on the milling forces in directions of x, y is the most significant, while the influence of the feed rate on the z-milling forces are the most significant. The calculation values from the milling force model are consistent with the experimental values. The results will provide a reliable theoretical guidance for milling of SiCp/Al composites, and it is feasible to predict the milling force during the milling of SiCp/Al by using this model.
Abstract: The material micro-hardness is used to reflect the plastic deformation within the localized shear band and the segment of saw-tooth chip. A high strength alloy steel Aermet 100 is taken as the workpiece material. The saw-tooth chip roots are obtained by cutting operation. The material micro-harnesses along the shortly initiated localized shear band, across the shortly initiated localized shear band and fully developed localized shear band, and within the segment are examined and analyzed. The localized shear band initiation and propagation are revealed by a new proposed model. The results show the localized shear band initiates firstly at the tool tip end of the primary shear band, and consequently another localized shear nucleates at the free surface end of the primary shear band. These two localized shears propagate face to face until the whole localized shear band is formed.
Abstract: Inconel 718 is widely used in aerospace, nuclear power and gas turbine industries. On the other side, it is well known as one of the most difficult-to-cut super alloy and its efficient machining assumes a lot of importance. Therefore, this paper presents an experimental investigation on the cutting force of Inconel 718 machined with several different kinds of cutting tools. Both single-factor and orthogonal experiments were carried out with cemented carbide, cermet and CBN tools. The effects of cutting tools and cutting parameters on the cutting force are investigated and the optimal cutting conditions are recommended.
Abstract: High-speed machining is investigated in a new viewpoint, thermodynamic theory. Many phenomena in cutting, such as heat conduction, chemical reaction, diffusion and so on, can be studied with thermodynamic theory. In this paper, entropy generation and entropy flow in cutting system are revealed as well as the interaction of sub processes. As a case study, the oxidation of cemented carbide tool was studied in thermodynamic theory and experiments. The results show that thermodynamic theory is effective.
Abstract: The cryogenic treatment is an extension of the cold processing technology by which the material properties could be changed. This provides a new method for people to improving the performance of the cutting tools and prolonging the tool life. The micro-structure of two unknown types of carbide reamers after different cryogenic treatment was introduced in this paper. From the metallographic microstructure, SEM microstructure, EDS spectrum analysis and the hardness measurement, the detailed analysis on the microstructure of the reamers (1# and 2#) was provided in this paper. The results show that the matrix materials of the two reamers were the WC-Co cemented carbide, and they were the ultra-fine grain carbide (＜500nm); 2# reamer belonged to the high Co cemented carbide reamer. By the cryogenic treatment, the hardness of two reamers has increased. And the value of the hardness for 1# reamer was higher than that for 2#.
Abstract: The failure progression of coated carbide tools in end milling of Inconel 718 superalloy was investigated. Tool wear was measured and failure mechanisms were discussed in the experimental process periodically. The experimental results indicated that the tool failure mechanisms were synergistic interaction among abrasive wear, adhesive wear, and fatigue wear. However, abrasive wear and adhesive wear were the main failure mechanisms at the beginning, fatigue wear prevailed the upper hand around the time when edge chipping appeared, and after edge chipping abrasive wear and adhesive wear dominated until the failure time. In addition, the macroscopic failure of the cutting tools is closely correlated to the nucleation and propagation of the crack under cyclic mechanical and thermal impact forces. Mechanical fatigue wear was the key form of fatigue wear at lower cutting speed, while at higher cutting speed thermal fatigue wear was the dominant fatigue wear.
Abstract: Three different cutting tools (ceramics CC6050, cubic boron nitride CB7025, carbide GC2025) were used for dry cutting of 3 groups of ADI which were heat-treated separately under different quenching temperatures. With the unified cutting parameters, the wear of tool flank of each cutter was studied and the main influencing factors of the wear were analyzed. Results showed that when the cutting parameters ap =0.2mm, f =0.16mm/r, vc =108m/min and the cutting tool was determined, the higher the quenching temperature was the lower the hardness of the test bars were and the tool flank wear was less; When the quenching temperature was determined, the more the produced BUE (build up edge) of the cutting tool was the less the tool flank wear was.
Abstract: In this paper the ball burnishing as a finishing process for sculptured surfaces is studied. This technique is a quick, easy and economical process for a significant improvement of high-end parts. Aiming at the burnishing of complex parts, different strategies are possible. In this case two strategies are presented: continuous burnishing (CB) using 5-axis interpolation and patch burnishing (PB) using 3+2 axis interpolation. Two parts have been previously machined in five-axis and then finished using ball burnishing techniques. The first one is an AISI 1045 hemisphere and the second one is a DIN 1.2379 part (64 HRC). Surface quality has been evaluated for both strategies obtaining a significant improvement of surface roughness and hardness.
Abstract: Titanium alloys are known for their strong chemical reactivity with surrounding gas due to their high chemical affinity, especially in dry machining. But it is very difficult to study the influence of surrounding gas on the tool-workpiece interface because of the machining processes’ complexity. In this paper, rotating pin-on-disc friction tests have been carried out at room temperature in ambient air and nitrogen gas to investigate the friction and wear behavior of WC-Co cemented carbide sliding against Ti6Al4V alloy. Scanning electron microscope (SEM) and Energy dispersive x-ray spectroscopy (EDX) have been used to examine the worn surface of the WC-Co pin and Ti6Al4V disc. The result shows that, compared to air, nitrogen gas brings a slight decrease in coefficient of friction, but a significant deduction in wear of the pin and disc. The SEM observation and EDX analysis indicate a distinct difference in wear mechanism between the pin and disc. Severe grooved wear, squeezing, adhering and tearing interactions are the main mechanisms causing the extensive wear of Ti6Al4V disc. Abrasion, adhesion and “pulling out” are the main mechanisms resulting in the wear of WC-Co pin.