Influence of binder systems on sintering characteristics, microstructures, and mechanical properties of PcBN composites fabricated by SPS

Abstract

Cubic boron nitride (cBN) with high hardness, thermal conductivity, wear resistance, and chemical inertness has become the most promising abrasive and machining material. Due to the difficulty of fabricating pure cBN body, generally, some binders are incorporated among cBN particles to prepare polycrystalline cubic boron nitride (PcBN). Hence, the binders play a critical factor to the performances of PcBN composites. In this study, the PcBN composites with three binder systems containing ceramic and metal phases were fabricated by spark plasma sintering (SPS) from 1400 to 1700 °C. The sintering behaviors and mechanical properties of the composites were investigated. Results show that the effect of binder formulas on mechanical properties mainly related to the compactness, mechanical performances, and thermal expansion coefficient of binder phases, which affect the carrying capacity of the composites and the bonding strength between binder phases and cBN particles. The PcBN composite with SiAlON phase as binder presented optimal flexural strength (465±29 MPa) and fracture toughness (5.62±0.37 MPa·m1/2), attributing to the synergistic effect similar to transgranular and intergranular fractures. Meanwhile, the excellent mechanical properties can be maintained a comparable level when the temperature even rises to 800 °C. Due to the weak bonding strength and high porosity, the PcBN composites with Al2O3-ZrO2(3Y) and Al-Ti binder systems exhibited inferior mechanical properties. The possible mechanisms to explain these results were also analyzed.

A new route to fabricate high‐performance binderless tungsten carbide: Dynamic sinter forging

“…It is seen that the cracks mainly propagate along the grain boundary for both the samples, accompanying with several intragranular fracture, while more intragranular fracture occurs in DSF sample rather than SF sample. Therefore, the improved fracture toughness must be mainly caused by the high toughness, defect‐free ultrathin grain boundaries 32 formed in the DSF samples, which requires a higher energy to fracture. In addition, the higher density of dislocations/stacking faults may contribute to the improved fracture toughness 33 for the DSF samples.…”

Synthesis of cBN-hBN-SiCw Nanocomposite with Superior Hardness, Strength, and Toughness

“…To comprehensively evaluate the mechanical properties of cBN-hBN-SiC w nanocomposites, the hardness, fracture toughness, and flexural strength of cBN composites with various additives reported previously are listed in Table 1 [ 4 , 24 , 29 , 45 , 46 , 47 , 48 , 49 ]. As shown in Table 1 , metal additives have the effect of toughening, but they cause a serious loss of hardness for cBN composites [ 14 , 46 , 47 ]. When introducing ceramic additives, the comprehensive mechanical properties of the cBN composites are obviously better than those prepared by using only metal additives [ 14 , 24 , 29 , 47 , 49 ].…”

“…As shown in Table 1 , metal additives have the effect of toughening, but they cause a serious loss of hardness for cBN composites [ 14 , 46 , 47 ]. When introducing ceramic additives, the comprehensive mechanical properties of the cBN composites are obviously better than those prepared by using only metal additives [ 14 , 24 , 29 , 47 , 49 ]. The mechanical properties of cBN composites can be further improved by introducing 2D materials such as Ti 3 AlC 2 and hBN [ 45 , 48 ], and 1D materials such as SiC whiskers and Al 2 O 3 whiskers [ 4 , 24 ].…”

“…Accordingly, two kinds of additives were extensively studied to fabricate cBN-based composites. One is metal additives of the groups IV, V, and VI of the periodic table and their compounds or other metallic elements such as aluminum, cobalt, and nickel [ 12 , 13 , 14 ]. Although metal additives can effectively reduce the sintering pressure and temperature, they adversely affect the mechanical properties of the composites.…”

Bioinspired PcBN/hBN fibrous monolithic ceramic: High-temperature crack resistance responses and self-lubricating performances

“…A series of additives containing α-Al 2 O 3 powder (80-100 nm, purity 99.9%, Jiangsu Lida High-Tech Special Materials Co., Ltd., Changshu, China), Si 3 N 4 powder (~20 nm, purity 99.9%, Beijing Huawei Ruike Chemical Co., Ltd., Beijing, China), AlN powder (~40 nm, purity 99.9%, Beijing Huawei Ruike Chemical Co., Ltd., Beijing, China), and Y 2 O 3 powder (~50 nm, purity 99.9%, Beijing Huawei Ruike Chemical Co., Ltd., Beijing, China) were added to the composites to promote sinterability. To promote the binding force of the fiber cells and cell boundaries, a binder system (Al 2 O 3 :Si 3 N 4 :AlN:Y 2 O 3 = 10:22:14:4) was simultaneously applied to both the fiber cells and cell boundaries [23]. The binder system in fiber cells was 50 wt%, whereas that in cell boundaries was 5 wt%.…”