Thermophysics characteristics and densification of powder metallurgy composites

Abstract

An analytical densification model describing the final stages of hot pressing and sintering has been developed and found to be consistent with empirical findings. The behaviour of composite powders for the matrices of diamond tools has been studied under hot pressing conditions. Differential scanning calorimetry was used to determine the heat capacity at constant pressure C p of pure Co, 663Cu, and composite iron-and cobalt based powders (also containing WC, Ni and 663Cu). The relationship between C p and composite densification has been analysed, and it has been found that optimised rare earth additions to the iron based composite powders can produce C p characteristics close or equivalent to that of pure Co powders. This modified composite powder has been used to hot press diamond drill and saw bits that show good properties. Employing a densification regime guided by the dynamic model has been found radically to improve stability in service (bend strength, hardness, impact, ductility and porosity).

Coating Process Investigation of DLC Coating Spinning Rings

“…When single DLC coating spinning rings are used in machine for 9 months in a row, the surface of some single DLC coating spinning rings will be damaged. In vie of this, surface treatment process of single DLC coating spinning rings is improved [2][3][4].…”

Key Program for Non-Equilibrium Phase Diagram of Ni 1 Type Steel

“…In complete eutectoid composition area, the temperature partition area from P 1 S 1 S 3 curve to P 2 S 2 S 4 curve is defined as complete eutectoid composition reaction area in this paper and the eutectoid reaction temperature partition area , in the left area of vertical lines of eutectoid composition 0.6%C ( or 0.53%C) as well as in the right area of vertical lines of eutectoid composition 0.8%C ( or 0.87%C) with the the temperature partition area from P 1 S 1 S 3 curve to P 2 S 2 S 4 curve are defined as incomplete eutectoid composition reaction area in this paper. Because space limited ,the test inspection is ommitted [1][2][3][4]…”

Doping Fe-based diamond tool matrix composites with a rare-earth element

“…The study involved hot-pressed agglomeration processing of diamond tool (matrix) composites with the rare earth by the doping method, the related service performance tests, and compared the test results for diamond tool (matrix) composites with the rare earth with those for composites free of the rare earth. The results have shown that the service performance of the Fe-based diamond tool (matrix) composites with the rare earth is obviously higher than that of the Febased diamond tool (matrix) composites free of rare-earth doping, the repeatability and stability of the experiment have reached a higher level [1,2].…”

“…Taken together, these components constitute the most common matrix formulation of hotpressed diamond tool composites. This reseach has mainly involved the preparation of Fe-based bonded powder doped with rare-earth cerium as an important point [1,2], the study of doping rare-earth cerium and the replacement of the expensive Cobased bonded powder in the above matrix formulation. Since the amount of the rare-earth additive is quite small, generally below 1 % of the gross amount of a binding agent, the cost of Fe-based diamond tool composites with the rare earth is very low.…”

“…Hot-pressed diamond tool composites are composed of diamond particles and the matrix, which includes cemented carbide bonded powder with WC as a framework, bronze-bonded powder with 663Cu as the main component, Co-based bonded powder with Co-Ni as the main constituent [1][2][3], etc. Taken together, these components constitute the most common matrix formulation of hotpressed diamond tool composites.…”