About Powder Metallurgy
Powder Metallurgy (‘PM’) is a fabrication technique that uses metal powder to manufacture complex industrial parts. It involves blending ultra-fine powdered materials, pressing them into a desired shape and then heating the compressed material to bond. The PM process generally consists of four basic steps: powder manufacture, powder blending, compacting, and sintering at high temperatures. Optional secondary processing often follows to obtain special properties or enhanced precision of those parts. The PM market is relatively large and shows high growth potential. Graphite for this market has to meet many challenging performance characteristics before it can be used.
Since the mid-1990s, synthetic graphite is mostly used due to its higher purity, consistency and particle size. High-purity graphite of greater than 99.5% Cg is preferred, with a particle size of around 5 microns. Presently, primary synthetic graphite is used and produced in a highly controlled graphitization process, which assures narrow specifications, consistent purity, perfect crystalline structure and well defined texture.
Graphite’s Role in Powder Metallurgy
Graphite is used in powdered metals as a source of carbon for the sintering process where it acts as a strengthening agent and as a lubricant. Graphite aids the release of PM parts from the die and is also used in conjunction with non-ferrous soft metals to provide self-lubrication (i.e. steel, brass and copper parts). The addition of graphite to ferrous parts, soft metals and ultra-hard alloys ranges from 0.2 to 3.5% of the total metal weight. Graphite is used because it is an excellent electrical and thermal conductor, it has outstanding lubrication properties and it is resistant to oxidation and cyclic temperature stress. It can withstand extreme temperatures while maintaining strength and shape. It is also inexpensive, light weight, easy to machine and replace compared to other materials.
The PM market is estimated to be worth US$24 Billion (~1.5Mt) annually of which the graphite portion is estimated to be US$200 Million (~20,000t) annually and growing at ~5% CAGR. Production of metal powders is practiced throughout the major industrial regions of the world with the largest market (at 80%) in the production of automotive PM parts. Based on forecast automotive demand, production of metal powders is expected to grow by 5% per year with the highest growth rate expected to be in Asia, where metal powder output is forecast to grow 9% per year. The demand for specified graphite in this market is expected to grow at the same rate as the overall PM market growth rate of 5% per year. Other uses for PM include specialized parts for military, aerospace, energy, medical, electronics, computers and household appliance applications.