A good understanding of the coating wear mechanism is essential in relation to tailoring the coating properties to the application, with a focus on increasing the tool performance. When a coated ...cemented carbide tool is applied in processes with high thermal and mechanical loads (e.g., hard turning process), the cutting tool can suddenly collapse with the deterioration of the coating. The focus of this research was to track the sequence of events that leads to the deterioration of coating materials (PVD TiAlN and MT CVD TiCN/Al
2
O
3
/TiN), to reveal the real wear mechanisms associated with coated cemented carbide cutting tools applied to hard turning. The tool wear was evaluated by focus variation microscopy (FVM) and scanning electron microscopy (SEM), before and after cutting edge collapse, during the hard turning of quenched and tempered AISI 4340 steel. The mechanisms associated with the progression of wear on MT CVD coatings involve abrasion, crack nucleation, propagation, the formation of crack networks, delamination, detachment between coating layers, and spalling. The deterioration of PVD coatings is related to the abrasion wear mechanism and the high deformation values at the cutting edge, which leads to the nucleation of cracks in the coating, reducing the bonding strength between the coating and the tool substrate, leading to spalling of the coating. The tool life of the PVD coating was three times longer than that of the CVD coating. The wear mechanisms acting on the coating is the main factor that influences the end of tool life.
The hard turning process is generally performed by PCBN or mixed ceramics tools, which have the mechanical properties that withstand the tribological conditions of the process imposed by the hardened ...machined material. Coated cemented carbides are also an option for hard machining processes, although relying on the coating deterioration. This paper aims to evaluate the tool wear rate in function of the cutting speed in the hard turning of the steel AISI 52100 with a hardness of 50 HRC for three different types of cutting tool materials: coated cemented carbide, mixed ceramic, and PCBN. The methodology applied to assess the tool wear is based on three-dimensional parameters (volumetric) obtained from a focus variation microscope (FVM). The tool wear rate (WR
RM
) is calculated based on ordinary least squares (OLS) adopting five values of
W
RM
in five machining time intervals. The face turning experiments were performed at four cutting speeds:
v
c
= 120, 150, 187.5, and 234 m/min. At
v
c
= 120 m/min, the PCBN presented the lowest tool wear rate (182 μm
3
/s); at
v
c
= 150 m/min, the coated cemented carbide (tool wear rate on the coating) had the best performance (417 μm
3
/s). The mixed ceramic tool presented a better performance at the higher cutting speeds of
v
c
= 187.5 and 234 m/min, 1206 and 1878 μm
3
/s, respectively. The methodology applied was reliable to understand and discuss the performance of the machining process through the tool wear rate (WR
RM
), which is based on the volume of removed material from the tool (
W
RM
). The three-dimensional tool wear parameters can also be applied to machining process optimization, cutting tool wear model creation, benchmarking, and development of new cutting tool materials and grades. Furthermore, the methodology can be considered more agile and precise when compared to the current industrial methodology of tool performance evaluation. Thus, this innovative methodology promotes important information for cutting tool manufacturers and for its customers such as automotive and aeronautic industry.
During internal threading, small alterations in cutting parameters, tool geometry, or process characteristics produce considerable effects on torque and temperature behavior. Understanding these ...effects is critical to the design and development of new taps. In this work, the torque behavior for a tap operation is evaluated as a function of the number of threads, tool manufacturer, and angle of the taper region of the tool. The chip–tool interface temperature was analyzed, considering the influence of cutting speed and number of threads. Experimental tests were carried out using M10x1.5 taps and cutting speeds of 10 m/min and 25 m/min. Taps with two different geometries were considered in this analysis. The results show a difference in the distribution of the torque along the threads of the conical part between the tools. The presence of adhered material increased the torque during the reverse stage. The torque during the reverse stage for a tap with a damaged tooth was approximately 50% of the torque during the cutting stage. The temperature showed an increase with the number of threads stabilizing between the fourth and fifth threads and increasing again in the sixth filled due to adhesion of workpiece material.
Mechanical components applied in ore crushing, the drilling of oil wells, and soil plowing need to be manufactured from materials with high resistance to abrasive wear, erosion, and corrosion. ...Typical materials applied under these severe conditions are cold work tool steels, high-speed steels and high-Cr white cast iron (HCWCI), which present a challenge in machining. In milling, the cutting fluid can easily access the cutting region due to interrupted cutting. In this context, coated cemented carbides associated with lubri-cooling techniques may be an alternative to improve the process feasibility. The aim of this study was to evaluate the effects of different coated cemented carbide grades and lubri-cooling techniques on the tool life and surface residual stress of the milled surface of HCWCI. Therefore, two coated cemented carbide grades associated with two lubri-cooling techniques (flood emulsion and liquid nitrogen—LN
2
) were applied in milling tests. The results demonstrated the feasibility of using the coated cemented carbide as a tool material in the milling of HCWCI (cutting time longer than 15 min). Furthermore, LN
2
increased, by at least a factor of 2, the tool life when compared with flood emulsion. Regarding the milled surface, values above 500 MPa were obtained for the compressive residual stresses with the use of the worn cutting edges and the application of LN
2
.
The development of new coated cemented carbide tool grades, based on grain refining and the unidirectional orientation of crystals in the coating layer, allows this material to withstand the severe ...tribological conditions imposed in hard turning. Previously, this was only possible using PCBN or oxide ceramic tool materials. The aim of this research was to determine the limiting conditions for two coated cemented carbide grades (with MT CVD and PVD coatings) aimed at allowing them to withstand at least a machining time of 15 min in the turning of hardened steels, considering the cutting parameters usually adopted for PCBN tools. Turning experiments were performed on AISI 4340, AISI 52100 and AISI D2 hardened steels, and the worn cutting edges were analyzed using focus variation microscopy (FVM) applying the three-dimensional wear parameters. The use of the PVD-coated cemented carbide grade was feasible in the case of AISI 4340 steel with a level of hardness up to 55 HRC, allowing a machining time longer than 30 min. For AISI 52100 and D2 steels, feasibility was only observed with hardness levels up to 50 and 45 HRC, respectively. Interestingly, in these cases, longer machining times were achieved using the MT CVD-coated cemented carbide grade. Wear and consequent coating layer deterioration were found to be the limiting factors for tool life, and the three-dimensional wear parameters allowed these to be identified. The results indicated the appropriate limiting conditions for the application of coated cemented carbide grades in hard turning as a function of the steel microstructure and level of hardness.
•Application of coated cemented carbide tools grades in turning of hardened steels.•Application of focus variation microscope (FVM) and volumetric wear parameters.•Criterion for tool life based on volumetric wear parameter.•Tool life is strongly associated with tools coating deterioration.•Coating deposition technique and steel microstructure influence the tool life.
Hard turning has been applied in a wide range of mechanical components based on ferrous materials. The application of these components is a function of mechanical properties and microstructure – that ...also has manufacturing process influences, i.e., cutting mechanism. This research aims to discuss the tool wear level and the correlation with the wear mechanisms in turning with PCBN tools, which deals with three steel alloys (AISI 4340, AISI 52100 and AISI D2) and considers six levels of hardness (on the interval from 35 to 60 HRC), applying the novel three-dimensional wear parameters based on Focus Variation Microscope (FVM) to wear evaluation. Considering the wear parameters that represent the amount of material removed from the tool (WRM) and tool affected area (WAA), tool wear intensity and abrasion wear mechanisms have a decreasing trend with the increase of hardness in the range of 35–50 HRC. Above 50 HRC, however, there is a tendency of increased tool wear intensity when steel hardness is increased. The fraction volume of carbides in the steel microstructures intensifies the abrasion wear mechanism. The adhesion wear mechanism showed a reduction with an increase of the steel's hardness – identified by wear parameters WAM (adhered material volume on the tool). Based on crater wear formation, the diffusion wear mechanism had an inverse behavior when compared to adhesion. Better results concerning tool wear can be achieved when turning steels with 50 HRC. It was evidenced that the three-dimensional wear parameters applied open new possibilities to understanding complex and specific phenomena occurring in machining processes, particularly in the machining of hardened steels.
•Three-dimensional wear parameters as a methodology to evaluate tool wear and wear mechanism.•Tool wear level and tool wear mechanism transition in the transition zone from continuous to hard turning – 50 HRC.•Steel microstructure impact in the tool wear and wear mechanisms.
Polycrystalline cubic boron nitride (PCBN) tools have high abrasion resistance and are thus suitable for application in the machining of steels with a high volume fraction of primary carbides in ...their microstructure. These tools are usually applied in the machining of steels with hardness above 45–50 HRC and in the case of application to steels with hardness below 45 HRC, the formation of an adhered layer on the rake face of the tools often occurs. This paper reports a study on the impact of the layer adhered on PCBN tools during the turning of AISI D2 steel, with 35 and 50 HRC. The microhardness and microstructure of the adhered material were determined, as well as the tool wear based on volumetric wear parameters. The layer adhered on the PCBN tool rake face has the same chemical elements as the machined steel alloy. Its microstructure is oriented in the direction of the chip flow and the primary carbides were fragmented. For the sample with 35 HRC the amount of material adhered (WAM) on the rake face of the PCBN tool was approximately 360% higher than the steel with 50 HRC. The material layer adhered on the PCBN tool rake surface in the case of the 35 HRC steel acts as an edge (assuming the cutting function), while for the 50 HRC steel, the adhered layer intensifies the adhesion wear mechanism through spalling on the tool rake face. The results obtained provide important information for the selection of materials and grades for the development of new cutting tools.
•Microstructure and hardness characterization of the layer adhered on PCBN tools.•Mechanisms of PCBN tool wear in the turning of AISI D2 with middle hardness value (35‐50 HRC).•The revelation of adhesion wear mechanism on the PCBN tool.•Machining process evaluated by three-dimensional (volumetric) tool wear parameters.
The finishing operation of transmission components in the automotive industry is widely performed by the hard part turning process, using polycrystalline cubic boron nitride (PcBN) as cutting tool ...material. Carburizing steels are used in shafts and gears, and after the heat treatment processes, the components have typically 10-30 vol% of retained austenite in the carburized layer. The hard-turning is essentially a process involving high temperatures. The temperature at the tool-chip interface typically reaches the austenitization temperature range of the machined steel. In carburizing steels, the consequence is the generation of crater wear in PCBN tools by the chemical wear mechanism. In this context, this research aims to determine the impact of the retained austenite in the carburized steels on the crater wear formation in the PcBN tools. The 18CrNiMo7-6 steel was used to manufacture the workpieces. During the heat treatment, two carbon potentials (0,64% and 0,72%) and two tempering temperatures (160 °C and 180 °C) were applied to reach two levels of hardness (710 HV and 740 HV) and amount of retained austenite (20% and 27%). To study the wear, hard-turning tests were performed, applying industrial cutting parameters. The PCBN inserts were analyzed by a focus variation microscope (FVM) and a scanning electron microscope (SEM). For the same level of hardness, an increased phase fraction of the retained austenite in the steel increases the crater wear of the PcBN tools. Two complementary hypotheses were framed to explain the results: i. the high fraction volume of retained austenite increases the overall oxidation potential of the iron on the steel, accelerating the chemical degradation of the cBN grains; ii. the high amount of retained austenite reduces the formation of the protective layer on the chip tool interface. The in-depth investigation of chemical degradation is a largely unexplored subject on the wear evaluation of the ultrahard cutting tool.
•The research is connected to the automotive industry and the production of transmission components.•The discussion of the hard-turning process in case-hardened steels.•The impact of the retained austenite in the case-hardened steels on the PCBN tool wear.•Discussion about chemical degradation in ultrahard cutting tools (PcBN).
Machining of Compacted Graphite Iron: A review Sirtuli, Larissa Juliana; Bello Bermejo, Juan Manuel; Windmark, Christina ...
Journal of materials processing technology,
11/2024, Letnik:
332
Journal Article
Recenzirano
Odprti dostop
Compacted Graphite Iron (CGI) represents a unique combination of the characteristics of grey and spheroidal cast irons, sparking significant interest over the past two decades, particularly as a ...favoured material in several automotive industry applications, including engine components and heavy-duty vehicle parts. Despite its growing prominence, the full potential of CGI remains underutilised, primarily due to its lower productivity rate compared to grey cast iron. This paper comprehensively reviews existing research on CGI machining, emphasising the challenges and exploring opportunities for development in this field. A detailed comparison between the machining of compacted graphite iron, grey cast iron and spheroidal graphite cast iron is provided, highlighting the unique characteristics associated with CGI. The influence of microstructure and chemical composition on machining processes is thoroughly examined and deliberated. Moreover, this review delves into the effects of various process variables on CGI machining, including cutting tools, lubrication, and cooling methods. The paper concludes by discussing potential future trends and innovations in CGI machining, offering a prospective outlook on how these developments could bridge the productivity and literature gap and enhance the utilisation of CGI in industrial applications.
Display omitted
•CGI machining must be more efficient to meet market demands and increase CGI use.•Focused research isolating variables is crucial for improving CGI machining.•Understanding CGI and tool interactions is key to enhancing CGI machining.•Clarifying how impurities and trace elements in CGI affect CGI machining is needed.•Advanced lubrication and cooling methods can boost sustainable CGI machining.
The wear of diamond-coated wire is an important cost driver in the multi-wire sawing of silicon-based photovoltaics. Understanding the different forms of diamond wire wear could help the solar energy ...industry to be more competitive by reducing wafer costs. In this study, an innovative method was applied to investigate the wear of diamond wires: several diamond grains in a diamond wire loop were tracked during the slicing of monocrystalline silicon. The grains attached to the wire were analyzed by scanning electron microscopy and focus variation microscopy. Based on the observed non-uniformity of wear on the perimeter of the cross-section of the wire, the rotation of the wire on its longitudinal axis was investigated. A new method that promotes wire rotation during cutting was successfully applied. The form and progression of the wear were also investigated by tracking single grains during the cutting process. Observations show the occurrence of nickel layer removal/deformation, micro-chipping of the diamond grains, abrasion wear, and sporadic grain pullout.
•Successful tracking of single grains during the cutting process to analyze the form and progression of the wear.•Method for promoting wire rotation during cutting.•Measurement of diamond protrusion height and comparison to the thickness of the mono-Si chips.
