The Preparation of Ag Nanopaste with Silver-Plated Diamond by Low-Temperature Pressureless Sintering

Diamond/Ag nanopaste has been prepared by mixing Ag nanoparticles, silver-plated diamond particles, and an organic solvent system. Then, we characterized and studied the sintering properties of diamond/Ag nanopaste. Meanwhile, the impact factor of sintering temperature on the sintered microstructure of the diamond/Ag nanopaste on direct bonding copper (DBC) substrate was investigated. The influences of sintering temperature on the shear strength of diamond/Ag nanopaste connection layer for attaching silicon chip on the silver-plated copper substrate were analyzed. The results show that silver plating on the surface of the diamond can significantly strengthen the bonding ability between the diamond and nano-silver. When the pressureless sintering temperature increased from 150 °C to 350 °C, the porosity of diamond/Ag nanopaste decreased from 29.8% to 8.9%, and the sintered diamond/Ag joint with uniform and dense connection layer showed the maximum shear strength of 15.26 MPa as sintering at 350 °C.

Improvement in Hardness and Wear Behaviour of Iron-Based Mn–Cu–Sn Matrix for Sintered Diamond Tools by Dispersion Strengthening

The work presents the possibility of fabricating materials for use as a matrix in sintered metallic-diamond tools with increased mechanical properties and abrasion wear resistance. In this study, the effect of micro-sized SiC, Al2O3, and ZrO2 additives on the wear behaviour of dispersion-strengthened metal-matrix composites was investigated. The development of metal-matrix composites (based on Fe–Mn–Cu–Sn–C) reinforced with micro-sized particles is a new approach to the substitution of critical raw materials commonly used for the matrix in sintered diamond-impregnated tools used for the machining of abrasive stone and concrete. The composites were prepared using spark plasma sintering (SPS). Apparent density, microstructural features, phase composition, Young’s modulus, hardness, and abrasion wear resistance were determined. An increase in the hardness and wear resistance of the dispersion-strengthened composites as compared to the base material (Fe–Mn–Cu–Sn–C) and the commercial alloy Co-20% WC provides metallic-diamond tools with high-performance properties.

Solutions of Critical Raw Materials Issues Regarding Iron-Based Alloys

The Critical Raw Materials (CRMs) list has been defined based on economic importance and supply risk by the European Commission. This review paper describes two issues regarding critical raw materials: the possibilities of their substitution in iron-based alloys and the use of iron-based alloys instead of other materials in order to save CRMs. This review covers strategies for saving chromium in stainless steel, substitution or lowering the amounts of carbide-forming elements (especially tungsten and vanadium) in tool steel and alternative iron-based CRM-free and low-CRM materials: austempered ductile cast iron, high-temperature alloys based on intermetallics of iron and sintered diamond tools with an iron-containing low-cobalt binder.

A Newly Developed Easily Sinterable Low-Alloy Steel Powder

The work presents a possibility of fabrication of inexpensive iron-based powders intended to form the matrix in sintered diamond-impregnated tool components. In this study, a finely dispersed, pre-alloyed steel powder, containing over 95 wt.% Fe, has been designed and fabricated by means of a proprietary process developed at AGH-University of Science & Technology. It has been shown that the experimental powder can be consolidated to a closed porosity condition (>95% theoretical density) by pressure-less sintering at a temperature below 900 °C. The as-consolidated material is characterized by an excellent combination of hardness (~250 HV) and mechanical strength (>1200 MPa in 3-point bending) that meets the diamond tooling requirements. Its properties can be modified to some extent by varying the cold forming pressure and sintering temperature.

Tool reliability of sintered diamond drill bit for processing silicon carbide ceramics based on Bayesian theory

Silicon carbide (SiC) ceramics, as a superhard nonmetallic material, would induce severe tool wear during drilling. To ensure the quality of processing, the drill bits must be replaced in advance before failure, which leads to serious waste without effective usage. Aiming at the tool reliability problem determined by the tool wear during drilling of the high hardness nonmetallic materials, this article proposed a reliability analysis method of sintered diamond drill bit for machining SiC ceramics based on the distribution of tool degradation increment and the modeling of gamma process, and a tool reliability model of degradation increment was established based on the Bayesian theory. The drilling experiment of sintered SiC ceramics was carried out by sintering diamond drill bit to obtain the degradation increment data. The accuracy of the model was tested by the reliability model deviation rate, which indicated that the reliability model with considering individual differences was more accurate. This research can provide a theoretical model and analytical method for improving the reliability of the nonmetallic brittle material processing tools.