EFFECT OF HOT ISOSTATIC PRESSING ON THE MECHANICAL-PROPERTIES OF COPPER-INFILTRATED LOW-ALLOY STEELS

Though copper-infiltrated steel parts close to full density can be pro duced, their mechanical properties, in particular impact strength, and tensile strength, are generally low compared to full density steel pa rts. It is possible to improve these mechanical properties when specia l infiltrating procedures such as vacuum infiltration, are used. This improvement has been attributed primarily to the elimination of uninfi ltrated pores, resulting in higher total density. In this study, conta inerless hot isostatic pressing (HIPing) at temperatures between 500-d egrees-C to 1100-degrees was used to assess the effect of the reductio n of pores on the impact and tensile properties of copper-infiltrated steel. Specimens with three different carbon contents (0.005, 0.45 and 0.82 w/o) were studied. A large improvement in impact strength withou t diminution of tensile strength was observed after HIPing. Unnotched Charpy Impact strengths larger than 405J and tensile strengths up to 6 25MPa have been obtained with specimens containing 0.45w/o carbon. The microstructural modifications of as-infiltrated specimens after HIPin g are related to the processing conditions, and the most significant f actors controlling the enhancement of the mechanical properties are di scussed.