Showing papers on "Tool wear published in 2014"

Problems and solutions in machining of titanium alloys

Abstract: Titanium alloys are known as difficult-to-machine materials The problems of machining titanium are many folds which depend on types of titanium alloys This paper investigates the underlying mechanisms of basic challenges, such as variation of chip thickness, high heat stress, high pressure loads, springback, and residual stress based on the available literature These are responsible for higher tool wear and worse machined surface integrity In addition, many cutting tool materials are inapt for machining titanium alloys as those materials are chemically reactive to titanium alloys under machining conditions To address these problems, latest techniques such as application of high pressure coolant, cryogenic cooling, tap testing, thermally enhanced machining, hybrid machining, and use of high conductive cutting tool and tool holder have also been discussed and correlated It seems that all the solutions are not yet well accepted in the industrial domain; further advancement in those fields are required to reduce the machining cost of titanium alloys

Evaluation of machining performance in cryogenic machining of Inconel 718 and comparison with dry and MQL machining

Abstract: There has been significant work on establishing relationships between machining performance and the cutting parameters for various work materials. Recent trends in machining research show that major efforts are being made to understand the impact of various cooling/lubrication methods on machining performance and surface integrity characteristics, all aimed at improving process and product performance. This study presents the experimental results of cryogenic machining of Inconel 718, a high-temperature aerospace alloy, and comparison of its performance in dry and minimum quantity lubrication machining. Experimental data on force components, progressive tool wear parameters such as flank wear, notch wear, crater wear, cutting temperature, chip morphology, and surface roughness/topography of machined samples are presented. New findings show that cryogenic machining is a promising research direction for machining of high-temperature aerospace alloy, Inconel 718, as it offers improved machining performance in terms of reduced tool wear, temperature, and improved surface quality. It was also found that the number of nozzles in cryogenic machining plays a vital role in controlling cutting forces and power consumption in cryogenic machining of Inconel 718.

Cutting performance and wear mechanism of nanoscale and microscale textured Al2O3/TiC ceramic tools in dry cutting of hardened steel

Abstract: Nanoscale and microscale textures with different geometrical characteristics were fabricated on the surface of the Al 2 O 3 /TiC ceramic tool, and molybdenum disulfide (MoS 2 ) solid lubricants were burnished into the textures. The effect of the textures on the cutting performance was investigated using the textured self-lubricated tools and conventional tools in dry cutting tests. The tool wear, cutting force, cutting temperature, friction coefficient, surface roughness and chip topography were measured. Results show that the cutting force, cutting temperature, friction coefficient and tool wear of nanoscale and microscale textured self-lubricated tools are significantly reduced compared with the conventional tool, and the developed tool with wavy microscale textures on the rake face is the most effective in improving the cutting performance. The textured self-lubricated tools increase the surface roughness of machined workpiece, while they can reduce the vibration for a stable cutting and produce more uniform surface quality. The chip topography is changed by the textured self-lubricated tools. As a result, the nanoscale and microscale textured self-lubricated tools effectively improve the cutting performance of conventional Al 2 O 3 /TiC ceramic tool, and they are applicable to a stable dry cutting of the hardened steel.

Tool wear mechanisms in the machining of Nickel based super-alloys: A review

Abstract: Nickel based super-alloys are widely employed in aircraft engines and gas turbines due to their high temperature strength, corrosion resistance and, excellent thermal fatigue properties. Conversely, these alloys are very difficult to machine and cause rapid wear of the cutting tool, frequent tool changes are thus required resulting in low economy of the machining process. This study provides a detailed review of the tool wear mechanism in the machining of nickel based super-alloys. Typical tool wear mechanisms found by different researchers are analyzed in order to find out the most prevalent wear mechanism affecting the tool life. The review of existing works has revealed interesting findings about the tool wear mechanisms in the machining of these alloys. Adhesion wear is found to be the main phenomenon leading to the cutting tool wear in this study.

Investigation of the effects of cryogenic treatment applied at different holding times to cemented carbide inserts on tool wear

Abstract: Cutting tool costs is one of the most important components of machining costs. For this reason, tool life should be improved using some methods such as cutting fluid, optimal cutting parameters, hard coatings and heat treatment. Recently, another one of the methods commonly used to improve tool life is cryogenic treatment. This study was designed to evaluate the effects of different holding times of deep cryogenic treatment on tool wear in turning of AISI 316 austenitic stainless steel. The cemented carbide inserts were cryogenically treated at −145 °C for 12, 24, 36, 48 and 60 h. Wear tests were conducted at four cutting speeds (100, 120, 140 and 160 m/min), a feed rate of 0.3 mm/rev and a 2.4 mm depth of cut under dry cutting conditions. The wear test results showed that flank wear and crater wear were present in all combinations of the cutting parameters. However, notch wear appeared only at lower cutting speeds (100 and 120 m/min). In general, the best wear resistance was obtained with cutting inserts cryogenically treated for 24 h. This case was attributed to the increased hardness and improved micro-structure of cemented carbide inserts. These improvements were confirmed through hardness, image processing, and XRD analyses.

Nano-scale multilayered-composite coatings for the cutting tools

Abstract: In machining, the tool life is one of the limiting criteria in the process; therefore, the development of wear-resistant material for the cutting tools is imperative. This paper presents a methodological approach to the design of nano-scale multilayered-composite coatings for cutting tools. A plasma-enhanced technology of filtered cathodic vacuum-arc deposition is used to coat the tools, which significantly extends the operational life of the cutting tools. Here, a three-layered architecture of coatings is proposed and each layer has a specific function. The engineered structural layers allowed for optimum combination of a high adhesion strength with the tool substrate and a minimum adhesion of the work material to the tool surface. The coating process is presented here alongside with the technological role of the layers. A study of the effect of the developed nano-scale multilayer composite coatings on the rates of tool wear was undertaken, and results were compared with the wear rates of uncoated and standard coatings. The results of a wide range experimental work are given in terms of flank wear and tool life for various machining conditions.

Comparison of tool wear mechanisms and surface integrity for dry and wet micro-drilling of nickel-base superalloys

Abstract: The study focuses on the surface integrity and wear mechanisms associated with mechanical micro-drilling of nickel-base superalloy (Inconel 718) under dry and wet cutting conditions. Mechanical and metallurgical characterization was undertaken using scanning electron microscopy (SEM), backscatter electron microscopy (BSE), electron backscatter diffraction microscopy (EBSD), transmission electron microscopy (TEM), focused ion beam (FIB) microscopy, nanoindentation, energy dispersive spectroscopy (EDS) and elemental analysis techniques. The surface integrity results revealed large scale near surface deformations with high dislocation density along with nanocrystalline grain structures both under wet cutting conditions, with evidence of recrystallisation and lower dislocation density for dry cutting. Cutting conditions play a significant role in determining the depth of the affected layer, the frequency of misorientations, the microstructures and the stored energy found there. The cutting temperature and use of coolant play a key role in the formation of the altered surfaces. Abrasion, diffusion and micro-chipping were found to be the main wear mechanisms for wet cutting compared to abrasion, high adhesion, macro-chipping and catastrophic failure for dry cutting. Adhesion of work-piece material to the tool associated with abrasion and diffusion processes is the main contributor to wear phenomena. The results are important in guiding the choice of cutting conditions for acceptable surface integrity.

Machining of titanium alloys

Abstract: Machinability and Machining of Titanium Alloys: A Review.- Cutting Tool Materials and Tool Wear.- Mechanics of Titanium Machining.- Analysis of Physical Cutting Mechanisms and Their Effects on the Tool Wear and Chip Formation Process when Machining Aeronautical Titanium Alloys.- Green Machining of Ti-6Al-4V under Minimum Quality Lubrication (MQL) Condition.- Ultrasonic Assisted Machining of Titanium.

Tool condition monitoring using K-star algorithm

Abstract: Cutting tools are required for day to day activities in manufacturing. Continuous machining operations lead tool to undergo wear. Worn out tools effect surface finish during machining. The dimensional accuracy of components is also compromised. Robust tool health is vital for better productivity. Hence, an online system condition monitoring of tools is the need of hour, promising reduction in maintenance cost with a greater productivity saving both time and money. This paper presents the classification performance of K-star algorithm. A set of statistical features extracted from vibration signals (good and faulty conditions) form the input to algorithm. In the present study, the K-star algorithm is able to achieve 78% classification accuracy.

Analysis and optimization of hard turning operation using cubic boron nitride tool

Abstract: The present work concerns an experimental study of hard turning of AISI 52100 bearing steel, with CBN tool The combined effects of process parameters (cutting speed, feed rate, depth of cut and cutting time) on performance characteristics (tool wear, surface roughness, cutting forces and metal volume removed) are investigated using ANOVA analysis The relationship between process parameters and performance characteristics through the response surface methodology (RSM) are modeled Moreover, Grey-Taguchi method, composite desirability function and genetic algorithm are used as multi-objective optimization approaches to find the process parameters values that optimize simultaneously the performance characteristics The results show that the cutting speed exhibits maximum influence on abrasive tool wear The depth of cut affects strongly the cutting forces; however, it has a negligible influence on surface roughness The cutting time has a considerable effect on all performance characteristics Though the optimization approaches predicted near similar results, the GA technique seems to be the most advantageous approach Finally, the proposed experimental and integrated approaches bring reliable methodologies to model, to optimize and to improve the hard turning process They can be extended efficiently to study other machining processes

Tool Condition Monitoring of Single-Point Dresser Using Acoustic Emission and Neural Networks Models

Abstract: Identification and online monitoring of the dresser wear are necessary to guarantee a desired wheel surface and improve the effectiveness of grinding process to a satisfactory level. However, tool wear is a complex phenomenon occurring in several and different ways in cutting processes, and there is a lack of analytical models that can represent the tool condition. On the other hand, neural networks are considered as a good approach to resolve the absence of an analytical or empirical model. This paper describes a method to characterize the dresser wear condition from acoustic emission (AE) signal. To achieve this, some neural network models are proposed. Initially, a study on the frequency content of the raw AE signal was carried out to determine features that correlate the signal and dresser wear. The features of the signal were obtained from the root mean square and ratio of power statistics at nine frequency bands selected from AE spectra. Combinations of two frequency bands were evaluated as inputs to eight neural networks models, which have been compared with their classification ability. It could be verified that the combination of the frequency bands of 28-33 and 42-50 kHz best characterized the dresser wear condition. Some of the models produced very good results and can therefore ensure the ground part will be within project specifications.

Wear behavior and cutting performance of CrAlSiN and TiAlSiN hard coatings on cemented carbide cutting tools for Ti alloys

Abstract: Recently, multicomponent CrAlSiN and TiAlSiN coatings have been developed in order to gain high hardness and good thermal stability. In this study, the influence of TiAlN, CrAlSiN and TiAlSiN coatings on the wear behavior and cutting performance of the carbide cutting tools was investigated in dry machining of a Ti–6Al–4V alloy. TiAlN, CrAlSiN and TiAlSiN coatings were deposited on tungsten carbide milling inserts by using cathodic arc evaporation. The deposited TiAlN, CrAlSiN and TiAlSiN possess high hardness of 31 ± 1 GPa, 36 ± 2 and 35 ± 2 GPa, respectively. After annealing at 700 °C in air, the hardness of the CrAlSiN and TiAlSiN still keeps as high as 35–36 GPa, while the hardness of TiAlN decreases to 26 GPa. The main wear modes for the TiAlSiN-, TiAlN coated- and uncoated tools are abrasion and adhesion. The nanocrystalline TiAlSiN coatings retard the tool wear as compared to the TiAlN-coated tools. At a high cutting speed of 350 m/min, the tool life of the CrAlSiN coatings exceeds the TiAlSiN-, and TiAlN-coated and uncoated tools by 2.9, 4.2 and 9.5 times, respectively. The CrAlSiN coatings show high wear resistances in dry machining of Ti–6Al–4V alloys, and thus possess the best cutting performance.