PURPOSE:To prevent the generation of the blown-out matter after mechanical removal of the infiltrated matter, by subjecting porous ferrous parts to a surface treatment by a nitriding treatment with a salt bath then heating the same to a specific temp. to blow out forcibly the infiltrated matter and removing mechanically the same. CONSTITUTION:A hard nitride layer is formed by a nitriding method with a salt bath on porous metallic parts such as ferrous sintered parts in order to improve the wear resistance thereof. Since the salt in the bath used in this case is infiltrated into the inside of the porous material, the parts are heated for 30- 60min at 200-300 deg.C to blow out forcibly the infiltrated matter onto the surface. The blown-out matter is thoroughly removed by shot blasting or shot peening. The generation of the succeeding blow-out is thoroughly prevented by such treatment, and the surface hardness of the sintered parts is further improved by a peening effect as a secondary effect.

Hanazawa Akihisa

Papers

Surface treatment of ferrous metallic parts