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In-situ formed Al-AlN sintered composite materials have been developed by the direct nitriding process based on the reaction of the aluminum matrix to nitrogen gas during sintering. A traditional press-sinter(P/S) method, hot extrusion(H/E) and powder forging (P/F) processes are available to consolidate the composite aluminum alloys. Fine AlN particles less than 1 μm in diameter dispersed as hard particles in the material have a significantly strong bonding to the matrix. They have an important role to improve wear resistance equivalent to the hard anodizing or Ni-P plating. The aluminum alloy also shows a low friction coefficient (less than 0.01) under oil lubricating conditions because fine AlN particles make it possible to form oil film at the interface between the counterpart material.

A sintered steel with a high rolling contact fatigue strength of 1660 MPa was developed using a new process and modified powder. It is expected to be used for heavy duty gears and races for automatic transmissions. The process consists of compacting, sintering, repressing and a deep carburization. It is a more simple process than the conventional one like hot powder forging and the repress-resintering process. The repressing is used to get a density of 7.4 g/cm3 and above. Another of its merit is a better dimensional tolerance and economic efficiency. Deep carburization is used to obtain a very hard surface layer and good mechanical properties by means of resintering pores upset by repressing. Some process parameters and chemical composition are to be discussed in terms of the rolling contact fatigue strength compared to wrought steels.