The study is motivated by the application of dry finish milling for post-build processing of additive Ti6Al4V blanks, since the use of neither lubricant nor coolants has been attracting increasing attention due to its environmental benefits, non-toxicity, and the elimination of the need for additional cleaning processes. For end mills, wear patterns were investigated upon finish milling of the SLM Ti6Al4V samples under various machining conditions (by varying the values of radial depth of cut and feed values at a constant level of axial depth of cut and cutting speed). When using all the applied milling modes, the identical tool wear mechanism was revealed. Built-up edges mainly developed on the leading surfaces, increasing the surface roughness on the SLM Ti6Al4V samples but protecting the cutting edges. However, abrasive wear was mainly characteristic of the flank surfaces that accelerated peeling of the protective coatings and increased wear of the end mills. The following milling parameters have been established as being close to rational ones: Vc = 60 m/min, Vf = 400 mm/min, a_p = 4 mm, and a_e = 0.4 mm. They affected the surface roughness of the SLM Ti6Al4V samples in the following way: max cutting thickness—8 μm; built-up edge at rake surface—50 ± 3 μm; max wear of flank surface—15 ± 1 μm; maximum adherence of workpiece. Mode III provided the maximum MRR value and negligible wear of the end mill, but its main disadvantage was the high average surface roughness on the SLM Ti6Al4V sample. Mode II was characterized by both the lowest average surface roughness and the lowest wear of the end mill, as well as an insufficient MRR value. Since these two modes differed only in their feed rates, their values should be optimized in the range from 200 to 400 mm/min.

Introduction. Wire arc additive manufacturing (WAAM), due to its “design as manufacturing” characteristic, is gradually becoming one of the most promising technologies. However, at present, there are no comprehensive comparative studies on the microstructure and mechanical properties of deposited samples made from austenitic stainless steel at different locations of the sample. In addition, their machinability remains insufficiently investigated. The purpose of this study is to compare the microstructure and mechanical properties of samples made of austenitic stainless steel ER321 (analogues – AISI 321, 0.08% C-18% Cr-10% Ni-Ti) obtained by the WAAM method at different locations within the sample and to assess their machinability by the magnitude of the components of the cutting force during end milling and the roughness of the machined surface. The properties and microstructure of samples obtained by wire-arc additive technology are investigated, and milling forces are investigated. The effect of the feed on the components of the cutting force and the roughness of the machined surfaces during conventional milling of ER321 steel workpieces using 12 mm diameter cemented carbide end mills with a wear-resistant AlTiN coating applied by physical vapor deposition (PVD) is determined. Research methods. The content of elements and the solidification pattern in various parts of the workpieces were determined using X-ray microanalysis. The microstructure of the samples was studied by a metallographic method. Stress-strain diagrams were obtained by tensile tests, and the microhardness of the samples was also measured. In comparison with the pattern of conventional milling of rolled workpieces, a pattern of changes in cutting forces and surface roughness was established depending on the feed rate during milling of deposited workpieces. Results and discussion. During deposition, ferrite with a vermicular morphology is primarily formed in the lower region of the sample, whereas austenite with a dendritic ferrite structure is observed in other regions. The microhardness values of the deposited and rolled samples are close, averaging around 230 HV0.1. The ultimate tensile strength of the rolled samples is 666 MPa, which is approximately 40 MPa higher than that of the deposited samples. During milling of the deposited workpieces, the lateral cutting force acting perpendicular to the feed direction is greater, and the surface quality is poorer. During milling of deposited workpieces, the lateral cutting force acting perpendicular to the feed direction is greater, and the surface quality is poorer. During milling of deposited workpieces, the feed force acting in the feed direction is greater under high feed rates.

Introduction. Unlike traditional manufacturing processes, additive manufacturing (AM) offers improved efficiency while being environmentally friendly. A significant limitation hindering the adoption of wire-based electron beam additive manufacturing (EBAM) technology is the relatively low quality and high surface roughness of 3D-printed parts. The purpose of this study is to establish the optimal values of milling process parameters (rotational speed, feed rate, and milling width) based on the simultaneous evaluation of the surface roughness of the machined surface and the material removal rate. Methods and materials. This study investigated specimens fabricated using EBAM technology. Uniaxial tensile tests were conducted on an electromechanical testing machine. Cutting forces were determined with a Kistler 9257B dynamometer. Milling studies of EBAM 321 steel workpieces were performed on a semi-industrial CNC milling machine. Results and discussion. It was shown that in order to increase the material removal rate and reduce the cutting force on a milling machine without the use of coolant, it is recommended to increase the milling speed, but not to increase the feed rate. To investigate the relationship between material removal rate and surface roughness relative to milling parameters on a semi-industrial machine (with an average stiffness of the portal frame), multiple linear regression models and nonlinear models based on feedforward neural networks were employed. It was demonstrated that linear regression models are sufficient for predicting optimal milling parameters. However, it should be noted that the study was conducted within a narrow range of gentle machining conditions, with short processing times and without accounting for tool wear. Under these constraints, the optimal milling parameters for EBAM 321 steel were predicted as follows: spindle speed of 4,500 rpm, feed rate S = 404 mm/min, and cutting depth B = 0.43 mm, resulting in a predicted surface roughness (Ra) of 0.648 µm and a material removal rate of 695 mm³/min.

Due to the unique microstructure and mechanical heterogeneity of austenitic stainless steel made via wire arc additive manufacturing (WAAM), its machinability differs significantly from that of rolled material. Accordingly, this study systematically investigates the influence of milling strategies on key process responses (cutting forces, surface roughness, vibration displacement, and temperature) to reveal the mechanisms of machining parameters during the milling of WAAM-fabricated austenitic stainless steel. The material used in this study is ER321 austenitic stainless steel. During deposition, the fusion zone cools more slowly than the transition zone; consequently, the fusion zone exhibits a hardness approximately 20 HV_0.1 lower than that of the transition zone. Surface roughness is primarily reduced by decreasing the primary feed per tooth. However, when the primary feed per tooth is small, ploughing is induced, which not only increases surface roughness by 25% but also causes abnormal increases in temperature and vibration displacement. Nevertheless, ploughing has little effect on the total milling force, and the feed per tooth shows a positive correlation with the total milling force. Tool run-out and an increase in the uncut chip thickness lead to a positive correlation between the radial depth of cut and the key process responses. Moreover, ploughing also occurs when the radial depth of cut is small. The axial depth of cut has almost no effect on the machining process. Moreover, a small-diameter mill leads to severe ploughing, and at a high table feed, climb milling leads to cutter offset.

The authors investigated the microstructure and mechanical properties of the samples obtained by the method of wire electron beam additive manufacturing (WEBAM), and their machinability by milling forces using the Taguchi method. Grains of previous austenite and annealed martensite were observed in the samples in various directions. The grains of the previous austenite grow along the surfacing direction and exhibit a pronounced orientation. On the lateral surface of the sample, the grains of the previous austenite are columnar, their hardness is approximately 505 HV _0.1 . On the upper surface of the sample, the grains of the previous austenite are isometric, their hardness is approximately 539 HV _0.1 . The degree of transformation into martensite varies in different parts of the sample. In the part close to the lateral surface, martensite is shallower and the previous austenitic grain boundaries are not observed. Its hardness is approximately 514 HV _0.1 . In the lower part of the sample, due to multiple thermal cycles, martensite decomposes, while its hardness is low and is approximately 480 HV _0.1 . In the upper part of the sample, martensite and the previous austeni­tic grain boundaries are observed, the hardness is approximately 513 HVelectron beam additive manufacturing, microstructure, hardness, machinability, martensitic stainless steel, Taguchi method. Due to the high hardness of the sample during climb milling, a stronger impact of the cutting edge on the sample leads to an increase in cutting force. Due to the low plasticity of the sample during conventional milling, a decrease in the volume of material pressed into the back surface of the tool leads to a decrease in cutting force. As the feed rate to the tooth increases, deformation of the material increases, the temperature increases, which leads to a decrease in the material strength. Reducing the material strength slows down the growth of cutting force.