An investigation on the sintering behavior of 316L and 17-4PH stainless steel powders for graded composites

摘要

This paper presents the densification and microstructure of bilayer structures made from 316L and 17-4PH stainless steels powders during sintering. The requirements for such objects could be magnetic properties at one area of the part and non-magnetic properties at another area of the object. A pressureless solid state sintering method in conjunction with a powder layering technique was used. The sintering was carried out at temperatures ranging from 1100 to 1340℃ for 120 min in hydrogen and vacuum atmospheres. Non-isothermal sintering behavior was also examined by dilatometric analysis. It was found that the strain rate of 17-4PH stainless steel powder is higher than that of 316L during the course of sintering. This induces mismatch strain between two layers that can be harmful for the co-sintering process. The amount of strain incompatibility is noticeably higher in vacuum sintering compared to hydrogen sintering. It has also been shown that the mismatch strain induces biaxial stresses during sintering, affecting the densification rate of the bilayer. An enhanced densification rate compared to the individual layers was noticed, particularly during vacuum sintering. A narrow interlayer diffusion boundary with high volume fraction of ferrite phase was realized.