PURPOSE: To improve the lubricity of an org. auxiliary and to make a product dense and large in size while reducing the amount of the auxiliary to be added by providing a lipophilic property to the surface of hydrophilic superhard powder to be mixed with other superhard powder using alkyl groups or the like.

CONSTITUTION: The surface of hydrophilic fine powder of WC, WC-TiC, Co, Al2O3 or the like is cleaned with benzene or acetone, and the powder is heat treated by an autoclave method using CeOH(C16H31OH),(C6H14) or the like. The resulting lipophilic powder is mixed with other lipophilic powder, and after adding a small amount of lubricating binder such as paraffin or glue, the mixture is molded and sintered. In this method, a large-sized product of high quality can be manufactured while reducing the amount of the additive.