Anthony Griffo

Fracture Resistant Super Hard Materials and Hardmetals Composite with Functionally Designed Microstructure

Abstract Polycrystalline diamond and other hard materials are widely used in earth boring, mining, and construction tool applications. Chipping and fracture resistance is often improved by various means at the expense of hardness and wear resistance. This trade-off between wear resistance and chipping resistance hinders the development of hard and super hard materials for many industrial applications. A new approach, characterized as “hard materials composites with functionally designed microstructure” including polycrystalline diamond and cemented tungsten carbide, is discussed. The functionally designed microstructure offers enhanced chipping resistance and toughness without significantly sacrificing wear resistance.

Lubricant type and amount effects providing high mechanical properties for a 2Cu-2Ni-0.9Mo-0.8C steel

Modern alloys have to meet the requirements of increased performance imposed by end user demands. For this reason, it is important to explore the compaction step which provides the first trend as far as density is concerned. This study examines three lubricants Acrawax, a polyvinyl fluoride, and Teflon, as well as the amount of Teflon (from 0 wt.% to 2 wt.%) mixed with the metal powders, and it demonstrates possible property and dimensional optimisation of a high strength low alloy (HSLA) steel containing 0.8 wt.% carbon - 2 wt.% copper - 2 wt.% nickel - 0.9 wt.% molybdenum.

Effects of sintering parameters on the mechanical properties of a Fe-2Cu-2Ni-0.9Mo-0.8C steel

Iron alloyed with nickel, copper, molybdenum and carbon was examined to determine the role of several processing parameters on the final sintered properties for densities in the range of 7.2 to 7.4 g/cm³. The study included the effect of compacting pres sure, sintering temperature and time, and lubricant amount, on the mechanical properties and dimensional variation. In addition, heat treatment was investigated. A systematic method was used to determine critical parameters and their interactions, while tailoring the microstructure. Thereafter, those parameters were tightly controlled whereas tolerable variations for other parameters were examined to reduce costs, without sacrificing final sintered properties. The study demonstrates possible property and dimensional optimisation for this steel. This procedure achieved an as-sintered strength of 940 MPa and a toughness of 29 J/cm², using a conventional single press, single sinter technology. Heat treatment resulted in a tensile strength over 1.2 Gpa while the toughness remained constant.