Impact of cutting fluid on hybrid manufacturing of AISI H13 tool steel

Purpose This paper aims to analyse the effects derived from the presence of residual coolant from machining operations on the Directed Energy Deposition of AISI H13 tool steel and the quality of the resulting part. Design/methodology/approach In the present paper, the effectiveness of various cleaning techniques, including laser vaporising and air blasting, applied to different water/oil concentrations are studied. For this purpose, single-layer and multi-layer depositions are performed. Besides, the influence of the powder adhered to the coolant residues remaining on the surface of the workpiece is analysed. In all cases, cross-sections are studied in-depth, including metallographic, microhardness, scanning electron microscopy and crack mechanism analyses. Findings The results show that, although no significant differences were found for low oil concentrations when remarkably high oil concentrations were used the deposited material cracked, regardless of the cleaning technique applied. The crack initiation and propagation mechanisms have been analysed, concluding that the presence of oil leads to hydrogen induced cracking. Originality/value High oil concentration residues from previous machining operations in hybrid manufacturing led to hydrogen induced cracking when working with AISI H13 tool steel. The results obtained will help in defining future hybrid manufacturing processes that combine additive and subtractive operations.

Design and Testing of a WAAM Retrofit Kit for Repairing Operations on a Milling Machine

Repairing, remanufacturing, and refurbishing high value metal components are crucial to move towards a more sustainable economy. Nowadays, repairing operations on high value parts, such as dies, are generally performed using time-consuming manual approaches that rely on the operator’s expertise. The research idea of this paper is to develop a retrofit kit to provide additive capabilities to an existing milling machine, allowing automatic repairing of components thanks to a fast switch between additive and machining operations without a relevant economic investment such the acquisition of a brand-new machine: the final cost of the solution is lower than 10% with respect to the mean cost of a 5-axis milling machine. The additive technology used in this work is Wire Arc Additive Manufacturing (WAAM) that is characterized by a higher deposition rate and a simpler and cost-effective equipment with respect to other techniques (e.g., laser cladding). The design of the system is illustrated in the paper together with the analysis of the results achieved repairing a test case: a die casting mold made of AISI H13 tool steel.

Influence of Selective Laser Melting Technology Process Parameters on Porosity and Hardness of AISI H13 Tool Steel: Statistical Approach

The correct setting of laser beam parameters and scanning strategy for Selective Laser Melting (SLM) technology is a demanding process. Usually, numerous experimental procedures must be taken before the final strategy can be applied. The presented work deals with SLM technology and the impact of its technological parameters on the porosity and hardness of AISI H13 tool steel. In this study, we attempted to map the dependency of porosity and hardness of the tested tool steel on a broad spectrum of scanning speed–-laser power combinations. Cubic samples were fabricated under parameters defined by full factorial DOE, and metallurgic specimens were prepared for measurement of the two studied quantities. The gathered data were finally analyzed, and phenomenological models were proposed. Analysis of the data revealed a minimal energy density of 100.3 J/mm3 was needed to obtain a dense structure with a satisfactory hardness level. Apart from this, the model may be used for approximation of non-tested combinations of input parameters.