Sakip Koksal

Cutting performance and wear characteristics of PVD coated and uncoated carbide tools in face milling Inconel 718 aerospace alloy

In this paper, cutting performance and failure characteristics of two PVD TiN coated and an uncoated tungsten carbide grades with identical geometry are presented. Face-milling tests of Inconel 718 superalloy were performed to investigate the effect of cutting speed and feed rate on tools performance under wet conditions. Tools were thoroughly examined under SEM at two stages in order to reveal the failure modes and wear mechanisms. These stages were after cutting for 5 s and when the tool failed. It was noted that the coating resulted in a marginal improvement, as it was delaminated by adhering workpiece material at the beginning of the cut, impeding the performance of the tool for the rest of the experiment. A combination of progressive chipping and flank wear was the general mode of tool failure, former being dominant at high speeds and the latter at the low speed region. Results showed that uncoated tool performed better than coated tools at low cutting speeds while coated tools gave slightly better performance as the speed was raised.

Wear Behavior of PVD and CVD Coated Carbide Tools when Face Milling Inconel 718

The wear behavior of two types of coated cemented carbide tools has been studied when face milling a nickel-based superalloy Inconel 718. PVD-TiN and CVD-TiCN+Al2O3 tools were used. It was found that the coatings were detached after only five seconds of cutting. An attrition type wear mechanism associated with workpiece material adhesion was observed which eventually led to severe chipping, flaking, plastic deformation and cracking. It was noted that the coatings had no significant effect on tool performance under the cutting conditions tested. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

Sliding Friction and Wear Behavior of Pack-Boronized AISI 1050, 4140, and 8620 Steels

This paper describes the dry sliding friction and wear performance of boronized AISI 1050, 4140, and 8620 steels with the Fe 2 B phase coating on the surface. The studies were carried out using a pin-on-disc arrangement. The disc material was made of carburized AISI 1020 steel. For the normalized (untreated) steels, two basic wear regimes were observed; namely, oxidative and severe metallic wear. In the oxidative regime, a low wear rate of 1E-5 mm 3 /Nm was found. The worn surfaces of the pins and discs were smooth and covered with patchy oxides. In severe wear, the wear rate was very high (1 E-3 mm 3 /Nm). The worn specimens were characterized by rough surfaces, plastic deformation, and metallic wear debris. Boronizing changed the wear mechanisms of steels. The test results showed that the boronized steels underwent oxidative fatigue wear with very low wear rate of 2 E-6 mm 3 /Nm. In addition, boronized steels exhibited lower friction coefficient than normalized steels at a sliding speed of 2 m/s.

Microstructural characterization and wear properties of in situ AlB2–reinforced Al–4Cu metal matrix composite

Aluminium matrix composites have been extensively studied for several decades due to the potential advantages over classical low-density materials. Low-density composites can offer high wear and corrosion resistance, high strength, and favorable thermal electrical properties that attract the attention of various industries such as aerospace and automotive. This study investigates the dry sliding wear behavior of AlB2–Al–4Cu composites with 5, 10, 20, and 30% weight reinforcement. In situ developed AlB2 flakes were incorporated as the reinforcing compound in the Al–4Cu matrix. The composite samples were tested against a steel disk using a pin-on-disk wear rig. The effect of reinforcement ratio, applied load, sliding velocity on the wear rate and friction coefficient of the composite samples was investigated. In addition, the worn surfaces have been characterized in terms of wear patterns. Compared to the matrix alloy, composite samples exhibited better wear resistance and lower friction coefficient to varying degrees of magnitudes.

Experimental optimization in turning of in-situ AlB2 reinforced AlMg3 matrix composites produced by centrifugal casting method

Ceramic particle-reinforced aluminum matrix composites are gaining attention especially from the automotive and aerospace industry requiring light-weight and high-strength materials for various applications. Since the AlB2 reinforced composites are relatively new materials, there is no investigation into the machinability of such materials in the literature. Therefore, the aim of this paper is to study machinability of AlB2/Al-Mg3 composite materials to optimize cutting force and surface roughness during turning operation. Taguchi’s statistical approach has also been utilized for the optimization of the process parameters. The optimum conditions providing the lowest cutting force and surface roughness were estimated. For the experimental planning, L8 (27) orthogonal array and the smaller-the-better response criterion were selected to obtain optimum conditions. Analysis of variance was used to determine the most significant parameters affecting the cutting force and surface roughness generated. The optimum condition was predicted from the combination of following factors and their respective levels; the second level of material type (AlB2/Al-Mg3), first level of cutting tool (TiN coating), first level of feed rate (0.08 mm/rev) and first level of cutting speed (350 m/min). Confirmation tests were performed to determine the effectiveness of Taguchi’s optimization method using the optimal levels of test parameters. A good agreement with a confidence level of 99.5% has been observed between the predicted and tests results for both cutting force and surface roughness.

The Characterization of WC-Co Based Materials Boronized within Molten Salt Bath

Coated WC-Co based cutting tool materials are widely used in machining applications. However some of the coating techniques, such as physical vapor deposition (PVD), involve only the physical deposition of coating layers which are prone to bulk delamination in some applications. Therefore functionally graded microstructure through diffusion is an efficient and widely used methods to improve the performance of coated WC-Co tools. In this work ISO P25, WC-Co based inserts were subjected to a thermochemical diffusion treatment by boronizing in a molten salt bath. The process was performed at 900, 1000, and 1100 °C for 1, 2 and 4 h. SEM, X-ray, EDS and microhardness analysis were performed on the samples. It was found that boron containing hard phases of W 2 B 5 , CoB, W 2 CoB 2 and WCoB were formed within the boronized region, occupying the grain boundary areas. An average microhardness value of 3600 HK 0.01 was measured in the near surface region which is substantially higher than the value of 1418 HK 0.01 representing the inner sections of the material.