Surface finishing of hard-to-machine cladding alloys for highly stressed components

Abstract

The supply and processing of materials for highly stressed components are usually cost-intensive. Efforts to achieve cost and resource efficiency lead to more complex structures and contours. Additive manufacturing steps for component repair and production offer significant economic advantages. Machining needs to be coordinated with additive manufacturing steps in a complementary way to produce functional surfaces suitable for the demands. Regarding inhomogeneity and anisotropy of the microstructure and properties as well as production-related stresses, a great deal of knowledge is still required for efficient use by small- and medium-size enterprises, especially for the interactions of subsequent machining of these difficult-to-machine materials. Therefore, investigations on these influences and interactions were carried out using a highly innovative cost-intensive NiCrMo alloy (IN725). These alloys are applied for claddings as well as for additive component manufacturing and repair welding using gas metal arc welding processes. For the welded specimens, the adequate solidification morphology, microstructure and property profile were investigated. The machinability in terms of finishing milling of the welded surfaces and comparative analyses for ultrasonic-assisted milling processes was examined focussing on surface integrity. It was shown that appropriate cutting parameters and superimposed oscillating of the milling tool in the direction of the tool rotation significantly reduce the mechanical loads for tool and workpiece surface. This contributes to ensure a high surface integrity, especially when cutting has to be carried out without cooling lubricants.

Investigations on influencing the microstructure of additively manufactured Co-Cr alloys to improve subsequent machining conditions

“…Schroepfer et al performed finish milling experiments on AM specimens of IN725 and compared the USAM with the CM. They have found that US causes significantly lower cutting forces compared to CM [19]. Similar results were obtained in investigations of Rinck et al on the influence of ultrasonic assistance on the machinability of Ti-6Al-4 V. Significantly reduced cutting forces due to US compared to CM were observed.…”

Wire and Arc Additive Manufacturing of a CoCrFeMoNiV Complex Concentrated Alloy Using Metal-Cored Wire—Process, Properties, and Wear Resistance

“…Wire and arc additive manufacturing (WAAM) is a fast emerging additive manufacturing technique and is utilized for a wide range of materials [11][12][13][14]. The main material focus in research is currently steel, aluminum, and titanium.…”

“…These materials are not always of the same chemical composition of the additively manufactured part. Such mixed material joints are commonly known in welding and possible to achieve, e.g., in explosion welding [28,29] or for cladding [14].…”

Digital Image Correlation for Measuring Full-Field Residual Stresses in Wire and Arc Additive Manufactured Components

“…Localised heating and uneven cooling during the WAAM process introduce large thermal gradients causing distortion and residual stresses, which can affect the topology and global integrity of a WAAM component [ 3 ]. In the last decade, WAAM induced residual stresses have been experimentally investigated for various alloys, such as steel [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ], aluminium [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ], titanium [ 3 , 13 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], nickel [ 13 , 29 , 31 , 32 , 33 ], intermetallics [ 21 , 34 , 35 ], etc. The aforementioned literature has focused on quite a few areas including but not limited to the effect of process and geometrical variables on residual stresses, the effect of interpass and side rolling on controlling/reducing residual stresses, and the effect of pre-and post-processing on residual stresses, etc.…”