Analysis of tool wear performance and surface quality in post milling of additive manufactured 316L stainless steel

Yadong Gong,Pengfei Li 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

Laser additive manufacturing (LAM) technology applied to the 316L stainless steel is attracting interest in the machining industry since it can shorten the production cycle and reduce numbers of machining steps. It still needs to be machined because of the poor surface quality, so the tool wear of post milling process after LAM needs to be studied. However, there are a few studies about the tool wear in milling of laser additive manufacturing stainless steel alloy. The aim of the paper is to evaluate the tool wear performance and surface quality when post milling the 316L stainless steel under different post milling (PM) time. The tool wear behavior was investigated using different analysis techniques. 3-D surface contour profilometer was used to measure the surface roughness and observe the morphology of small area; digital optical ultra-depth microscope analysis was carried out to evaluate tool wear and broken; the wear width of the blade was an indicator of the degree of the tool wear; different post milling methods were also compared. The obtained results demonstrate that the height of the LAM parts were connected with the heat dissipation effect; there are three stages of tool wear: initial wear stage, normal processing stage, and severe broken stage; usually the down-milling is better than up-milling at the bottom surface roughness, quality and edge morphology.

Experimental study on micro-grinding force and subsurface microstructure of nickel-based single crystal superalloy in micro grinding

Yadong Gong,Yunguang Zhou,Xuelong Wen,Jun Cheng,Yao Sun,Lianjie Ma 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7

Nickel-based single crystal superalloy has no grain boundary, which leads to the removal mechanism difference between single crystal material and polycrystalline material. Firstly, the removal mechanism of grinding nickel-based single crystal superalloy is analysed. Then, the developed prediction model of the tangential force F t and the normal force F n are established. Forthermore, the impacts of grinding parameters on grinding force and microstructure of grinding surface and sub-surface are analysed. Finally, some measurements to reduce or prevent recrystallization are proposed. As a result, the most shear slipping planes of nickel-based single crystal superalloy are {111} planes; with the increasing of the feeding rate and grinding depth, the micro-grinding force and the thickness of subsurface plastic deformation increase; the micro-grinding force and the thickness of subsurface plastic deformation decrease with the increasing of spindle speed. These results have some theoretical and engineering significance to the production of single crystal material parts.

Experimental study of micro-milling mechanism and surface quality of a nickel-based single crystal superalloy

Qi Gao,Yadong Gong,Yunguang Zhou,Xuelong Wen 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1

Micro-milling is widely used as a method for machining of micro-parts with high precision and efficiency. Taking the nickel-based single-crystal superalloy DD98 as the research object, the crystal characteristics of single-crystal materials were analysed, and the removal mechanism of single-crystal micro-milled parts was described. Based on molecular dynamics, a simulation model for nickel-based single-crystal superalloy DD98 micro-milling was established. Based on the response surface method of central composite design, the influences of spindle speed, feed rate, and milling depth on the surface roughness were examined, and a second-order regression model of the DD98 surface roughness was established. Using analysis of variance and the residuals of the model, a significant influence on surface roughness was found in the following order from large to small: Feed rate, spindle speed, and milling depth. Comparisons were conducted between the micro-milling experimental values and the predicted model values for different process parameters. The results show that the model fit is relatively high, and the adaptability is good. Scanning electron microscopy analysis of the micro-milling surfaces was performed to verify the slip and the removal mechanism of single-crystal materials. These results offer a theoretical reference and experimental basis for micro-milling of single-crystal materials.

Additive/subtractive hybrid manufacturing of 316L stainless steel powder: Densification, microhardness and residual stress

Yuying Yang,Yadong Gong,Shuoshuo Qu,Bo Xin,Yunchao Xu,Yang Qi 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12

316L stainless steel specimens were manufactured by additive/subtractive hybrid manufacturing (ASHM). The densification level, microstructure, microhardness and residual stress characterization in the different zones of the part were investigated. The density was determined by the Archimedes method, and the density measurement was divided into three regions, namely, the bottom, middle and top zones. The results show that the middle zone has a much smoother melting surface and that a relative density of nearly 100 % was achieved for the part in this study. The hardness profiles at room temperature, along the width and height directions of the cross-section of the top and bottom zones, were also studied. The residual stress was evaluated by X-ray diffraction (XRD) for the 316L SS specimen fabricated by the ASHM process, and it was compared with a specimen manufactured by the additive laser directed energy deposition (DED) process. The results show that the top and bottom zones exhibit tensile stress, and compressive stress occurs in the middle area. Moreover, the residual stress of ASHM shows a slightly smaller trend than that of the simplex DED due to the stress relaxation of the subsequent subtractive milling. These results may offer guidance for ASHM-fabricated 316L parts.

SOMEDGRA: A case retrieval method for machine tool product configuration design

Pengjia Wang,Yadong Gong,Hualong Xie,Yongxian Liu 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7

Case based design is an intelligent method which involves retrieving the most similar previous case to provide a solution of a new decision problem. However, conventional case based design approaches are too reliant on experts’ experiences. A new case retrieval method SOMEDGRA that combines Self-organizing map (SOM) and Euclidean distance (ED) method as well as Grey relational analysis (GRA) method is proposed in case based design. SOM is used to reduce the retrieval range and increase the retrieval efficiency, and ED is used to evaluate the similarity of cases comprehensively. To ensure that the final case has the best overall performance, an evaluation method of similar cases based on GRA is proposed to evaluate similar cases to select the most suitable case. The case study and result on an HTC series machine tool product show that the proposed method is effective, accurate and rapid in the process of product configuration.

Experimental research on micro mill-grinding AISI 1045 steel with a cold spraying compound micro cutting tool

Xuelong Wen,Yadong Gong,Chao Wang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.12

Micro mill-grinding is a novel compound machining process. This article presented a novel micro mill-grinding tool fabricated by cold spray technology. Compound tools with various grit sizes were used in sidewall machining and slotting. It is proved the effect of micro mill-grinding is better in sidewall machining. The machined surface topography and roughness were measured and the results were compared with those of micro milling. It shows that the smaller the grit size is, the smaller the surface roughness is, and the surface textures by compound tools also get tinier and denser with the decrease of the grit size. The influences of processing parameters on sidewall machining were investigated. It is found that surface roughness increases with the increase of cutting depth and feed rate, but decreases with the increase of spindle speed. The plastic deformation was found in the experiments by different machining methods, but there was no microstructure alternation. The plastic deformation of the specimen surface layer is smaller with the high cutting speed and slow feed speed in micro mill-grinding. The microhardness of the processed surface in micro milling-grinding is larger than that in micro-milling. The major wear mode of the micro mill-grinding tools is grit shedding or coating peeling off.

Experimental research on preparation of TiC coated micro-grinding tools and influencing factors of coating properties

Xuelong Wen,Fengbing Han,Yadong Gong 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

In this paper, coated micro-grinding tools with high wear resistance are successfully manufactured by vacuum multi-arc ion plating method, aiming at improving the grinding performance and prolonging the service life of micro-grinding tools. The principle of vacuum multi-arc ion plating is analyzed. Single factor coating experiment is conducted on the surface of specimens to investigate the effect of different preparation parameters on coating properties. It demonstrated during the present research that the interfacial reaction between metal titanium coating and diamond abrasive particles produces metallurgical bond. Meanwhile, the interpenetration between titanium coating and cobalt and nickel binder layer improves the binding force of the coating, which can firmly wrap diamond particles and slow down the shedding of diamond abrasive particles. When the arc current is 100 A, the voltage of the electromagnetic coil is 20 V and the deposition time is 2.5 h, coating properties with high wear resistance can be obtained.

Effect of post-heat treatment on the microstructure and mechanical properties of laser metal deposition Inconel 718

Pengfei Li,Jianzhong Zhou,Yadong Gong,Xiankai Meng,Jinzhong Lu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7

The microstructure, hardness, and fracture strength of Inconel 718 fabricated with laser metal deposition are investigated. The solution treatment plus aging (STA) (including 980 °C, 720 °C, and 620 °C for 1, 8, and 8 h, respectively) and low-temperature stress-relief annealing (LTSLA) (including 650 °C for 1 h) are compared, which can respectively improve the hardness and tensile properties. Results show that the as-deposited sample mainly contained γ matrix, coarse Laves phase, granular carbides, and nitrides. STA and LTSLA post-heat treatments could respectively improve the hardness and tensile properties, while the elongation slightly decreased. The solution treatment promoted almost Laves phase to dissolve into γ matrix and homogenized the matrix, and the aging treatment promoted the precipitation of γ′ and γ′′ phases, which significantly improved the mechanical properties.