Mechanical Properties and Microstructures of Mo₂C Strengthened Vanadis 4 Extra Alloy Steel by Powder Metallurgy and Heat Treatments

Abstract

In this work, different ratios of molybdenum carbide (1, 3 and 5 mass% Mo 2 C) powders were added to Vanadis 4 extra alloy steel powders and then mixed by ball milling for 6 h. The composite powders underwent vacuum sintering at 1 200, 1 220, 1 240, 1 260 and 1 280°C for 1 h, respectively. The results showed that the optimal sintering temperature for the addition of 5 mass% Mo 2 C powders was 1 220°C. It also represented that the apparent porosity was 0.18%, and that a transverse rupture strength (TRS) value of 2 281.3 MPa and a hardness value of 79.2 HRA were obtained, respectively. Additionally, the TRS value was obviously enhanced to 2 437.6 and 2 491.4 MPa by the addition of 5 mass% Mo 2 C powders after heat treatment and sub-zero plus heat treatments, respectively. Meanwhile, the hardness value also increased to 80.6 and 81.3 HRA, respectively, whereas the Mo-rich M 6 C carbides distributed in the grain boundaries, and V-rich MC carbides appeared in the grain and grain boundaries after sub-zero plus heat treatments. Significantly, a series of heat treatment processes is effective in improving the microstructure and strengthening the mechanical properties of the sintered Vanadis 4 extra composites.

Investigation of the strengthening mechanism and corrosion behaviours of Vanadis 4 extra tool steel adding ZrC−TiC powders through vacuum sintering, and sub-zero and heat treatments

“…Generally speaking, the morphology and sizes of carbides are used to roughly judge the type of carbides. Besides, our previous study indicated that the identification of MC and M 6 C carbides can be carried out by a combination of EDS and XRD measurements [18]. In this work, EDS analysis results further confirmed that the refined carbides of the 1350°C-sintered Z1.8T1.2 specimen mainly belonged to V-rich MC carbides.…”

In situ TEM observation of the microstructure characteristics of the vacuum sintering, sub-zero and heat treatments of Vanadis 23 high-speed steel by adding Cr3C2–TaC–TiC powders

“…It can be improved the mechanical properties by using a series of heat treatments. Cryogenic treatment (also known as sub-zero), as an effective way to improve the properties of tool steels, since it enhances the transformation of retained austenite to martensite [15][16][17][18]. Therefore, we added Cr 3 C 2 -TaC-TiC carbides to Vanadis 23 powders as an innovative composite material, aimed to explore a series of vacuum sintering processes, sub-zero and heat treatments for Vanadis 23 composites, and further examined the effects on the sintering behaviour, strengthening mechanism, and mechanical properties of Cr 3 C 2 -TaC-TiC strengthened Vanadis 23 composite materials.…”

Investigation of the vacuum hot pressing process on the mechanical properties, microstructures and material characteristics of Ni–35Mo–15Cr alloys

“…Moreover, since the Mo 2 C carbides have refined particle size and uniform distribution, high-temperature strength of γ/NiMo alloys prepared by this dispersion strengthening process could be greatly improved [2]. Our previous study also showed that the hardness and strength values of the materials improved when the amount of Mo 2 C phase was increased [17]. As shown in Figure 2(b), where the crystal structure is gradually dominated by the hexagonal (Mo 2 C) structures as the sintering pressure increased.…”

“…A scanning speed of 0.01 v·s −1 , initial potential of −2.0 V, and the final potential of 2.0 V were controlled. The polarisation curve was obtained by Corr-View software to analyse and compare the corrosion potential ( E corr ), the corrosion resistance ( R corr ) and corrosion current ( I corr ) of the different sintering parameters [17]. Moreover, the voltage is V (volts) vs. SCE (saturated calomel electrode).…”