The Assessment of the Transversal Rupture Strength (TRS) and Hardness of WC-Co Specimens Made via Additive Manufacturing and Sinter-HIP

Abstract

This study is focused on the mechanical properties of WC-Co composites obtained via Selective Laser Sintering (SLS) using PA12 as a binder. The as-printed samples were thermally debonded and sintered, first in a vacuum, and then sinter-HIP (Hot Isostatic Pressure) at 1400 °C, using 50 bar Ar, which has led to relative densities up to 66%. Optical metallographic images show a microstructure consisting of WC, with an average grain size in the range of 1.4–2.0 µm, with isolated large grains, in a well-distributed Co matrix. The shrinkage of the samples was 43%, with no significant shape distortion. The printing direction of the samples significantly impacts the transversal rupture strength (TRS). Nevertheless, the mechanical strength was low, with a maximum of 612 MPa. SEM images of the fracture surface of TRS samples show the presence of defects that constitute the cause of the low measured values. The hardness values position the obtained composites in the medium coarse classical cemented carbides range. The results were also related to the amount of free Co after sintering, close to the initial one, as assessed by magnetic measurements, indicating a low degree of interaction with PA12 decomposition products.

Microstructure and Properties of Fine-Grained WC-10Co-0.5Cr3C2-1TaC-0.5Ru Prepared by Rolling Ball Milling and Low-Pressure Sintering

“…It was found that the relationship between the hardness of WC-Co and the average distance between the grains of cemented carbide is feasible, which is related to its microstructure [10]. Among the ultra-fine cemented carbide grades, where the WC grain size is <0.5 µm, the parts exhibit high hardness, which can prevent deep penetration of abrasives and thus have high wear resistance [11].…”

Effects of Sinter-HIP Temperature on Microstructure and Properties of WC–12Co Produced Using Binder Jetting

“…The second group includes multiple-step processes, in which forming and densification are performed at separate stages with different equipment. Namely, the most relevant are as follows: fused deposition modelling (FDM) [12,13], selective laser sintering (SLS) [14], in which the fusion occurs only in the polymer shells of the powders, and binder jetting additive manufacturing (BJAM) [15][16][17][18]. Multi-step processes combine the forming of a green-body with a subsequent thermal treatment (debinding-sintering) as in traditional powder metallurgy.…”