Machining Parameter Optimization in High-Speed Milling for Inconel 718 Curved Surface

Machining technology for nickel-based alloy Inconel 718 is a hotspot and difficult problem in industrial fields and the high-speed milling (HSM) shows obvious superiority in difficult-to-process material machining. As the machining parameters are crucial in processing of Inconel 718 and the study of chip is important in metal cutting, there is an urgent need for deep research into the machining parameter optimization based on chip variation in HSM for Inconel 718 curved surface, so as to further increase the productivity of Inconel 718 in aerospace field. Regarding Inconel 718 curved surface, an experimental study about the machining parameter optimization based on chip variation in HSM is conducted. The relationship between chip shape and machining parameters is studied, and the roughness is measured and discussed for the machined curved surface. Results indicate that the chip area relates to geometric feature of curved surface, the optimal range for spindle speed is from 9000 to 11000 rpm based on chip variation, the feed per tooth should be large in case that condition permitted, and the cutting depth can be selected according to other constraint conditions. This study is significant for improving the machining quality and efficiency of Inconel 718 curved surface.     

Feasibility analysis and process characteristics of selective laser ablation assisted milling Inconel 718

Laser-assisted machining (LAM), as one of the most efficient ways, has been employed to improve the machinability of nickel-based superalloys. However, the conventional LAM process usually used high power laser with large spot size, easily leading to high processing costs and overheating of bulk materials. In this paper, a new approach of selective laser ablation assisted milling (SLA-Mill) process for nickel-based superalloys was proposed, in which low power laser with small spot size was used to selectively ablate the uncut surface in front of the cutting tool, resulting in plentiful surface defects emerging. Such defects would significantly weaken the mechanical strength of difficult-to-cut materials, which was different from the thermal "softening" principle of conventional LAM. Thus, the laser ablation effect with low power and small spot size was first studied. The relationship between process parameters (e.g., laser power, cutting speed and cutting depth) and process characteristics of SLA-Mill (e.g., chip morphology, tool wear and surface integrity) was systematically discussed. Moreover, the chip formation mechanism in the SLA-Mill process was indepth analyzed. Results show that the SLA-Mill process is an effective approach for enhancing the machinability of nickel-based superalloys. The resultant cutting force has a reduction of about 30% at laser power of 60 W, cutting speed of 90 m/min, and cutting depth of 0.1 mm. Furthermore, the chip formation, tool wear, and surface integrity have improved significantly. In general, this paper provides a new route for the application of LAM technology.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00384-9     

Experimental Investigation to Optimize Tool Life and Surface Roughness in Inconel 718 Machining

In addition to the cutting conditions, the surface quality is also affected significantly by a worn tool in machining processes. Identification of the desirable tool life so that the surface quality is maintained within a desirable level is an essential task, especially in the machining of hard materials. In this paper, an optimal tool life and surface quality were identified in the turning operation of Inconel 718 Superalloy by means of experimental investigations and intelligent methods. First, the effect of machining time (MT) at the different cutting parameters was widely investigated on the surface roughness using the neural network model. Then, the modified Non-dominated Sorting Genetic Algorithm (NSGA) was implemented to optimize tool life and surface roughness. For this purpose, a new approach was implemented and the MT was taken into account as the input and output parameters during the optimization. Finally, the results of optimization were classified and the suitable states of the machining outputs were found. The results indicate that the implemented strategy in this paper provides an efficient approach to determine a desirable criterion for tool life estimation in machining processes.     

Surface Integrity Investigation for Milling PA 6/MWCNT

In this study, surface integrity of polyamide 6/multiwalled carbon nanotube composite has been investigated after end-milling. Nanocomposite samples were produced with 3.5 wt% of filler using friction stir process. X-ray diffraction and scanning electron microscopy were used to study properties of the fabricated nanocomposite. The end-milling was carried out at different levels of spindle speed and feed per tooth to study the resulting surface integrity. Optical microscopy was used to analyze surface morphology. According to the results, surface quality increases due to decrease of feed per tooth and increase of spindle speed. Additionally, carbon nanotubes improve surface quality.     

An Investigation on Turning Hardened Steel Using Different Tool Inserts

Turning of hard materials usually presents poor machinability. However, for high productivity, it is desirable to employ turning of hard materials rather than grinding. In this work, turning of hardened 16MnCrS5 steel with hardness of 43 HRC was explored to judge machining performance with plain and wide-groove-type chip-breaking TiC-coated carbide inserts under dry and wet environmental conditions, different cutting velocity, and feed. Tool wear tests were also done in dry and wet conditions. Satisfactory tool performance was observed under wet condition using TiC-coated plain and wide-groove carbide inserts even at 268 m/min cutting velocity, when dry machining could not be done effectively.     

Effect of Machining Parameters on Surface Integrity in High Speed Milling of Super Alloy GH4169/Inconel 718

Control of surface integrity is a vital consideration in the machining of components subjected to fatigue loading, for example, critical components of aerospace engines. In this research, three important aspects of surface integrity of a machined part—surface roughness, micro-hardness, and residual stresses—were analyzed for their variations with the cutting parameters. Finish milling of super alloy GH4169/Inconel 718 was carried out using coated cemented carbide and whisker-reinforced coated ceramic inserts. All of the three machining parameters—cutting speed, feed rate, and depth of cut—were found to have a substantial effect on the surface integrity of the finished part. Although different cutting parameters gave different effects for the two types of cutting inserts, overall better surface integrity was obtained at minimum cutting feed and medium cutting speed and depth of cut value. Moreover, carbide inserts produced better surface integrity of the finished part, whereas ceramic inserts generated very high surface tensile stresses and poor surface finish due to back striking of the adhered metal chips.     

Experimental Investigation on Turning of Double Metal Composite with Network Interpenetrating Structure

The interpenetrating double metal phase composite is anisotropic. According to the structural and mechanical properties, the cutting process becomes more complicated. In this work, experimental investigation was systematically studied by means of turning experiments, and focused on cutting force and surface roughness; extra attention has been paid to the cutting phenomena in the zone of reinforcing phase and bimetal interface. Cutting force performance is similar to the ordinary materials, but there are several impact forces in cutting process. In addition, it is easy to produce cracks and exfoliations at metal/metal interface. These phenomena will lead to the decline of the machined surface quality.     

Experimental Study of Surface Roughness and Tool Flank Wear during Hybrid Milling

Two advanced machining methods such as thermally enhanced machining and ultrasonic-assisted machining are recently considered in many studies. In this article, a new hybrid milling process is presented by gathering the characteristics of these two methods. In order to determine the axial depth of cut and engagement in the process, three-dimensional thermal finite-element analysis is applied to determine the dimensions of softened materials. Finite-element modal analysis is used to determine the dimensions and clamping state of the workpiece while cutting area has the highest vibration amplitude. Full factorial experimental design is applied to investigate the effect of hybrid machining parameters on the surface roughness and tool wear. Tool flank wear was investigated under the condition of constant cutting speed during different period of times. Hybrid milling process with an amplitude of 6 µm and a temperature of 900°C creates a surface with 42% lower roughness in comparison to conventional milling in feed 0.08 mm/tooth. In a study of tool flank wear, the results show that application of TEUAM decreases flank wear at least 16% in comparison to all other processes.     

Study of standard heat treatment on mechanical properties of Inconel 718 using ball indentation technique

The effect of standard heat treatment on the microstructure and mechanical properties of Ni–Fe base super-alloy, Inconel 718 was studied by optical microscopy and ball indentation technique (BIT) using small amount of specimen. In order to get good ductility, good formability, yield, tensile and creep rupture, as-received material was given the standard heat treatment, viz solution treatment at two temperatures 940 °C and 1040 °C for1 h and water quenched (WQ) followed by aging treatment at 720 °C for 8 h. and furnace cooling (FC). The BIT has revealed that the strengths for as-received material are maximum compared to other heat-treated materials. After solution treatment there has been a radical decline in strength. But the ageing causes a significant enhancement of strength. Optical microscopy studies supported the obtained BIT results. γ″-phase is the basic strengthening phase in 718 alloys.     

Experimental study on moldability and segregation of Inconel 718 feedstocks used in low-pressure powder injection molding

Moldability and segregation of feedstock are linked to the rheological behavior of the powder-binder mixture. In this study, the impact of binders on viscosity and segregation of feedstocks was investigated. The experiments were conducted on several feedstocks obtained by mixing Inconel 718 powder with paraffin wax-based binder systems. The viscosity of feedstocks was measured by a rotational rheometer while the segregation within green parts was evaluated using a thermogravimetric analyzer. It was demonstrated that the variation in solid loading within a molded part can be measured with a sensitivity of at least ±0.25?vol% of powder. The results indicated that the predominant powder-binder separation appears clearly at the top and the bottom of the molded part. It was also shown that the viscosity profiles of feedstocks and the intensity of segregation depends significantly on the binder constituents used in feedstock formulation. The mixture containing only paraffin wax produced the best trade-off between high moldability and low segregation for an injection process requiring an extended time range between injection and solidification of the part (e.g. up to 10?min). For a short processing time (e.g. <1?min spent in molten state), the feedstocks containing paraffin wax with stearic acid or small amount of ethylene vinyl acetate can be also considered as good candidates for LPIM process because their viscosity and segregation potential are relatively low.     

Inconel718合金扩散连接接头的组织与性能研究

对细晶Incone1718高温合金无中间层和加Ni箔中间层两种情况下的扩散连接进行了研究,分析了不同的连接温度、连接压力、连接时间等工艺参数对接头剪切强度的影响;通过SEM、EPMA和金相技术对接头微观组织和力学性能进行了分析.确定了获得优质接头的最佳工艺参数区间,即扩散连接温度T=1 050℃,连接压力P=20 MPa,连接时间t=45 min,选用Ni箔作为中间层,厚度为25 μm.     

Effect of TiC Content on Mechanical Properties and Microstructure Evolution of TiC/Inconel 718 Functionally Gradient Materials by Direct Energy Deposition

TiC/Inconel 718 functionally gradient materials are prepared by direct energy deposition technology. The effect of TiC content on microstructure and mechanical properties of TiC/Inconel 718 functionally gradient materials is studied. With the increase of TiC content, the microhardness and carbide grain of the specimen are improved, and the density is reduced. The grain of the specimen changes from columnar dendrites to equiaxed crystal, and the equiaxed crystal size is decreased with the increase of TiC content. However, when TiC content is above 10 wt%, the number and size of the Laves phase, coarse TiC primary, and TiC secondary dendrite are increased which causes the generation of cracks. When the TiC content is above 5 wt%, the size of carbide and the number of cracked UMT increase and the impact toughness decreases. Therefore, the optimal maximum TiC content of TiC/Inconel 718 functionally gradient materials is 5 wt% when the laser power is 2200 W.     

Experimental study on the wear evolution of different PVD coated tools under milling operations of LDX2101 duplex stainless steel

Duplex stainless steels are being used on applications that require, especially, high corrosion resistance and overall good mechanical properties, such as the naval and oil-gas exploration industry. The components employed in these industries are usually obtained by machining, however, these alloys have low machinability when compared to conventional stainless steels. In this work, a study of the wear developed when milling duplex stainless-steel, LDX 2101, is going to be presented and evaluated, employing four types of milling tools with different geometries and coatings, while studying the influence of feed rate and cutting length in the wear of these tools. Tools used have been provided with two and four flutes, as well as three different coatings, namely: TiAlN, TiAlSiN and AlCrN. The cutting behavior of these tools was analyzed; data relative to the cutting forces developed during the process were obtained; and roughness measurements of the machined surfaces were executed. The tools were then submitted to scanning electron microscope (SEM) analysis, enabling the identification of the wear mechanisms that tools were subjected to when machining this material, furthermore, the early stages of these mechanisms were also identified. All this work was done with the goal of relating the machining parameters and cutting force values obtained, identifying, and discussing the wear patterns that were observed in the coating and tools after the milling tests, providing further information on the machining of these alloys. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00401-5     

Investigation of die radius arc profile on wear behaviour in sheet metal processing of advanced high strength steels

Advanced high strength steels (AHSS) are increasingly used in sheet metal stamping in the automotive industry. In comparison with conventional steels, AHSS stampings produce higher contact pressures at the interface between draw die and sheet metal blank, resulting in more severe wear conditions, particularly at the draw die radius. Developing the ability to accurately predict and reduce the potential tool wear during the tool design stage is vital for shortening lead times and reducing production cost. This paper investigates the effects of draw die geometry on the sheet metal tool wear distribution over the draw die radius using numerical and experimental methods. A numerical tool wear model is introduced and applied using the commercial software package Abaqus. Channel bend tests are carried out using an Erichsen sheet metal tester to verify the numerical model. Various geometries of radius arc profiles, including standard circular profiles, high elliptical profiles, and flat elliptical profiles, are numerically investigated, and the wear volume and contact pressure distribution along the radii are determined. The results show that the profile of the draw die radius has a significant effect on the wear distribution, and that a low contact pressure distribution can be achieved by using a combination of circular and high elliptical curved geometries.     

Experimental Investigation on Rotary Ultrasonic Face Grinding of SiCp/Al Composites

SiCp/Al composites have been widely used in many fields such as aerospace, automobile, advanced weapon system, etc. But this kind of material, especially with high volume fraction, is difficult to machine due to the reinforced particles existing in matrix, which has limited its further application. Rotary ultrasonic machining (RUM) has many excellent features and it has never been used to machine SiCp/Al composites. In order to improve the machinability and application of SiCp/Al composites, the rotary ultrasonic face grinding experiments of SiCp/Al composites reinforced with 45% volume SiC particles were carried out to investigate cutting force, surface quality, tool wear, and abrasive chip shapes. The experimental results indicate that ultrasonic vibration could reduce cutting force, surface roughness, surface defects, and increase plastic removal ratio. The cutting force could be lowered by an average of 13.86% and the surface roughness could be lowered by an average of 11.53%. The examined results of tool wear patterns suggest that tool wear is mainly caused by grain breakage and grain fall-off. Grinding wheel blockage and grinding burn were not observed in machining process.     

纳米结构陶瓷涂层的外圆磨削力以及磨削表面精度的实验研究

使用功率计监测磨削加工的能量消耗，探讨了纳米结构陶瓷涂层的外圆磨削过程；对纳米陶瓷涂层和传统陶瓷涂层在磨削力和磨削表面精度方面进行了比较．磨削实验使用了外圆磨床和陶瓷结合剂金刚石砂轮．通过测量主轴功率获得切向磨削力，讨论了加工参数，如切深、进给率以及砂轮粒度对切向磨削力的影响．还对磨削后的涂层表面用粗糙度仪和扫描电镜进行了评估，揭示了表面粗糙度与加工参数的关系．     

Investigation on tribological performance of CuO vegetable-oil based nanofluids for grinding operations

With ball-bearing and tribofilm lubrication effects, CuO vegetable oil-based nanofluids have exhibited excellent anti-wear and friction reduction properties. In this study, CuO nanofluids were synthesized by a one-step electro discharge process in distilled water containing polysorbate-20 and vegetable oil as a nanoparticle stabilizer and source of fatty-acid molecules in the base fluid, respectively. Pin-on-disk tribotests were conducted to evaluate the lubrication performance of synthesized CuO nanofluids between brass/steel contact pairs under various loadings. Surface grinding experiments under minimum lubrication conditions were also performed to evaluate the effectiveness of the synthesized nanofluids in improving the machining characteristics and surface quality of machined parts. The results of pin-on-disk tests revealed that adding nanofluids containing 0.5% and 1% (mass fraction) CuO nanoparticles to the base fluid reduced the wear rate by 66.7% and 71.2%, respectively, compared with pure lubricant. The lubricating action of 1% (mass fraction) CuO nanofluid reduced the ground surface roughness by up to 30% compared with grinding using lubricant without nano-additives. These effects were attributed to the formation of a lubrication film between the contact pairs, providing the rolling and healing functions of CuO nanoparticles to the sliding surfaces. The micrography of ground surfaces using a scanning electron microscope confirmed the tribological observations.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00314-1     

适用于直写式3D打印陶瓷浆料的流变学性能研究

目的 提出用于直写式3D打印陶瓷浆料的制备方法 和应满足的性能.方法 通过对4种不同陶瓷原料粉末的粒径分布进行表征,将4种粉末制备成浆料并测量其流变学性能,分析不同阶段高分子的引入对浆料流变学性能的影响.结果 对于较小孔径(250μm和150μm)的打印过程,原料粉末粒径绝对值需小于3μm且d90和d10的差值需小于2...     

直流电晕放电单环VOC降解特性的实验研究

利用高压直流电晕分解O2 和H2 O簇射出强氧化性自由基 (O、OH°、HO2 等 )来降解单环的挥发性有机物。选取了甲苯和苯作为实验研究的对象 ,分别对电晕放电特性以及放电电压、反应物浓度、湿度和停留时间的变化对降解效率的影响进行了研究。最后对苯和甲苯的降解机理作了较为详尽的分析。研究发现 :电极通气中的氧气含湿量对放电的V I特性有影响 ,通过调节流量和湿度能够产生比较稳定的流光电晕。放电电压、反应物浓度、湿度和停留时间对甲苯和苯的降解都有重要影响。在一定的工况下 ,甲苯的降解率可以达到 80 % ,而苯的降解率也在 70 %以上。实验结果表明 ,用自由基簇射技术脱除VOC是可行的也是与有效的。     

固体火箭发动机粘接界面湿热老化实验

对固体火箭发动机粘接界面试验件进行了不同湿热条件下的加速老化试验,并测量了不同老化时间粘接界面的扯离强度,描述了湿热老化试验和性能测试中的试验现象,结合复合材料微粘接结构吸湿规律对试验现象和撤离强度随老化时间变化曲线进行了分析。研究结果表明:衬层-推进剂粘接界面是固体火箭发动机粘接结构中最薄弱环节,应予以重点考虑;湿热老化促进了环境水分从衬层–推进剂界面向推进剂内部的扩散和渗透,致使弱边界层向推进剂内部扩展,导致了衬层-推进剂界面粘接强度的降低。试验件平均扯离强度随老化时间呈下降趋势,中间有一个强度趋于稳定的平台期。 