In situ modification of case-hardening steel 16MnCr5 by C and WC addition by means of powder bed fusion with laser beam of metals (PBF-LB/M)

Abstract

Typical high-strength products are made from carbon-rich steels possessing relatively high carbon content, thus reducing weldability. In this work, preliminary studies on designing and tailoring a low-alloyed steel for the laser-based powder bed fusion (PBF-LB/M) process by adding carbon black (C) nanoparticles and tungsten carbide (WC) particles for enhancing the material properties are provided. First, the base material 16MnCr5 is modified with different concentrations of C and WC. It was found that an increased C and WC content resulted in an elevated material hardness in the as-built state. However, this comes at the cost of a poorer processability as pore formation increased for C-modified and crack tendency increased for WC-modified 16MnCr5. When applying a post-process quenching and optional tempering heat treatment, material hardness in the range of 615 HV can be achieved for C-enriched 16MnCr5 in the tempered state, which would be suitable for bearing and gearing applications. The addition of WC particles favored an improved wear resistance which is twice as high as the one of C-modified material for similar material hardness, showing the enormous potential of WC addition for reducing the wear rate. Complementary SEM and EDX analyses show that both the dilution and bonding zone of the WC particles are affected by the processing conditions and the WC concentration. Furthermore, it was found that a nearly defect-free fabrication of WC-enriched 16MnCr5 was possible for up to 2.5 wt.-% of WC, proving that the occurring defects are highly sensitive to the WC concentration.

Experimental Investigations in the Processing of AISI H11 Powder Blends Enriched with Tungsten Carbide Nanoparticles for the Additive Manufacturing of Tailored Hot Working Tools in the Directed Energy Deposition (DED-LB/M)—Impact of Tungsten Carbide Nanoparticles on Microstructural and Mechanical Characteristics

“…In [37], the processing of the case hardening steel powder 16MnCr5 enriched with C-np or WC micro particles was extensively examined. Through the modification of the 16MnCr5 with 0.3 wt.-% C-np, the hardness increased from about 337 HV5 for the pure 16MnCr5 specimen to about 458 HV5 for the one reinforced with 0.3 wt.-% C-np.…”

Processing of Carbon Nanoparticle-Enriched AISI H11 Tool Steel Powder Mixtures in DED-LB/M for the AM of Forging Tools with Tailored Properties (Part II): Influence of Nanoscale Carbon Additives on Microstructure and Mechanical Properties

“…Due to the induced grain refinement and microstructural changes, the mechanical properties of manufactured specimens (e.g., hardness, tensile strength, yield strength or wear resistance) significant improve compared to the specimens manufactured out of unmodified base materials. These phenomena were investigated for varying combinations of base materials and nanoparticle powders [23][24][25].…”

On the Influence of Volumetric Energy Density and Inter-Layer Time on the Material Properties of Case-Hardening Steels

“…Comparable hardness values could be obtained after hardening even though the process-specific fine microstructure might negatively affect the carbon diffusion. Furthermore, the first approaches in the field of in situ alloying were carried out for the low-alloyed steel 16MnCr5 with the goal of substituting these energy-intensive carburizing processes [14,15]. When aiming at avoiding these processes, e.g., via the application of in situ alloying approaches, a profound understanding on the microstructure formation in the as-built state is necessary.…”