Direct additive laser manufacturing using gas- and water-atomised H13 tool steel powders

Abstract

To date only gas-atomised tool steel powders have been used for direct laser additive manufacturing and the potential benefits of using water-atomised powders have not been explored. As the use of the process in the rapid tooling field is growing, there is a need to explore if the less expensive wateratomised materials can be realistically utilised. A comparative investigation is described, using gas-and water-atomised H13 powder deposited with a CO 2 laser and coaxial powder feed nozzle. Multiple layer wall dimensions, composition, microstructure, surface finish and hardness are related to process conditions and the causes of the observed phenomena are discussed. An energy-balance method is used to model the temperature of the powders and the results used to explain some of the effects. Results indicate that using the lower cost water-atomised powder still allows a metallurgically sound component to be built and does not significantly affect surface finish. The build rate is, however, lower and the water-atomised powder tends to produce slightly softer walls, attributable to a higher temperature during tempering of deposited material by subsequent laser passes.

Freeform Laser Consolidated H13 and CPM 9V Tool Steels

“…Repeatedly, the prior deposited layers went through multiple thermal cycles, which finally tempered the major portion of the LC steels except the top several deposited layers of the thin wall. This is exactly the case for the LC H13 steel, which also agreed with the observation on the LENS-and DMDproduced H13 steels [9,13,17,29,30]. Comparatively, the LC CPM 9V steel acted slightly differently, the microstructure in the slightly ''dark'' region at the top of each deposited layer, which was thermally affected by the immediate deposition of the subsequent layer, exhibits partially dissolved eutectic phase at the inter-cellular regions due to re-austenitization during re-heating, but less affected by thermal-cycle-induced tempering.…”

“…H13 tool steel has already been widely investigated by LENS and DMD processes [9,13,17,29,30]. In contrast, CPM 9V steel belongs to a family of novel CPM tool steels, which possess substantially improved abrasive wear resistance in combination with enhanced toughness and heat check resistance due to the presence of a high amount of primary vanadium carbides in the matrix [28].…”

Evaluation of Strain-Rate Sensitivity of Selective Laser Melted H13 Tool Steel Using Nanoindentation Tests

“…due to its strong temper resistance and ability to maintain high hardness and strength at elevated temperatures [1][2][3][4][5][6][7][8]. During working processes such as die casting, tool steel molds are heated using molten metals, which is then followed by cooling.…”

“…Hot-work tool steels fabricated by conventional methods require expensive dedicated tools and thus are not suitable for small-scale production and the production of complex shapes [5][6][7]. An additive manufacturing (AM) technique, which builds parts from 3D digital models typically by a layer additive process, has been an effective method to solve these problems [9][10][11][12][13][14].…”

Application of direct laser melting to restore damaged steel dies

“…Direct laser melting (DLM) technologies offer the advantages of single-stage production and geometric flexibility [1]. DLM technologies, which possess the capability to produce parts directly from metal powders, have been used to restore damaged mold surfaces.…”