Mechanical Properties of High‐Speed Steel AISI M50 Produced by Laser Powder Bed Fusion

Abstract

The microstructure and mechanical properties of high‐speed steel AISI M50 (80MoCrV42‐16, Mat. Nr. 1.3551), produced by laser powder bed fusion (LPBF), are analyzed. The mechanical properties in hardened and tempered condition are characterized by hardness, fatigue strength, and toughness and compared with the properties of conventionally produced samples. Moreover, the effects of an additional posttreatment by hot isostatic pressing (HIP) on the microstructure and mechanical properties are investigated. Dilatometric testing is used to investigate the influence of the different initial microstructures on hardening. All heat‐treated samples expose a fine martensitic microstructure with high hardness. The conventionally produced samples show a band‐like orientation of carbides due to the production by vacuum induction melting and vacuum arc remelting followed by a hot working process. This carbide structure is bypassed by the rapid cooling in the LPBF process. The LPBF samples show a comparable hardness after hardening and tempering to the conventionally produced material. In heat‐treated state, the LPBF samples show a low fatigue strength. Posttreatment by HIP included in the heat‐treatment chain significantly increases the fatigue strength. Nevertheless, the fatigue strength is still lower compared with the reference material. Both LPBF grades show a low toughness compared with the reference material.

Improved the microstructures and properties of W−Mo−V high‐speed steel by laser additive manufacturing and niobium alloying

“…In the mechanical manufacturing industry, highspeed steels have excellent heat strength, hardness, superior cutting performance and wear resistance and are routinely used in cutting tools, cold dies and rolls [1,2]. These excellent properties mainly depend on the presence of high content of alloy carbides in the microstructure of high-speed steel.…”

Crack-free in situ heat-treated high-alloy tool steel processed via laser powder bed fusion: microstructure and mechanical properties

“…To reduce the thermal gradient and thus avoid crack formation induced by thermal stresses, substrate plate heating is applied during the LPBF fabrication of various materials. Several studies have been performed using substrate plate temperatures of 200-400 C on HSS steels with relatively low carbon content, e.g., HSS M2 [6,7,8] and the HSS M50 [9], all yielding similar defect patterns, i.e., cold cracks. Furthermore, substrate plate heating has been demonstrated to reduce crack density, defect frequency [10,11], and residual stresses in H13 hot work tool steel [12].…”

Improving the Fatigue Strength of Laser Powder Bed‐Fused AISI M3:2 by Hot Isostatic Pressing

“…[4,5] The processability and microstructure of high-speed steels M2 and M50 produced by LPBF have been also investigated. [6,7] With preheated powder bed, tools with even higher carbon content can be processed. [8,9] Summarily, tool steels produced by LPBF present a martensitic matrix with retained austenite in the as-built condition.…”

“…In addition, the risk of thermal stresses, resulting in cold cracks or warping, increases with carbon content. [9,10] The fatigue strength of parts manufactured by LPBF is lower than the conventionally produced material, [7,11] since pores and lack-of-fusion defects can lead to stress concentration and promote crack growth. [12] Hot isostatic pressing (HIP) is applied to densify the material at high temperature and high pressure to improve the fatigue strength of these parts.…”

“…[12] Hot isostatic pressing (HIP) is applied to densify the material at high temperature and high pressure to improve the fatigue strength of these parts. [5,7,13,14] An HIP device with an integrated quenching facility can even combine the heat treatment and HIP densification into one step, which is a promising post-treatment method for AM parts. [15] AISI M3:2 is a highly alloyed high-speed steel (HSS) with good wear resistance and high hardness.…”