Volume 53, Issue 5

The microstructures of dissimilar metal welds between 9Cr-1Mo (Modified) (P91) and austenitic stainless steel (AISI 304) with Ni-based alloy interlayers (Inconel 625, Inconel 600 and Inconel 800H) are reported. These interlayers were deposited by the friction surfacing method one over the other on P91 alloy, which was finally friction welded to AISI 304. In this paper, the results of microstructural evolution in the friction surfaced coated interlayers (Inconel 625, 600, 800H) are reported. For comparative purposes, the microstructures of consumable rods (Inconel 625, 600, 800H) and dissimilar metal base metals (P91 and AISI 304) were also reported. Friction surfaced coatings exhibited dynamic recrystallization. In friction surfaced coatings, the carbide particles were found to be finer and distributed uniformly throughout the matrix, compared to their rod counterparts.

In the third century AD, replicas of small denomination coins were manufactured in the border areas of the Roman Empire. They are composed of an iron core with a non-ferrous metal layer and are called “Subferrati”. Four roman coins, one of them from Loig, two of them from Enns, and one of them from Magdalensberg, were metallographically prepared and examined in the LOM, SEM-BSE, and by means of XRF. The non-ferrous metal layers are composed of lead-containing bronzes with segregation structures from a α-copper solid solution, Sn-rich δ-phase, and Pb. Spherically shaped iron inclusions could also be observed in the bronze coating. They can be attributed to the fact that the iron core was dipped in liquid bronze. The coins' iron cores mainly contain ferrite and little pearlite. Elongated inclusions originate from the iron manufacture in the bloomery furnace and subsequent forging. The Neumann lines are in the ferrite formed during minting. Copper could also be observed on the ferrite grain boundaries (so-called liquid metal embrittlement) which suggests a contact of the liquid non-ferrous metal with the iron core. Based on the present results, no indications of different mints or other coating methods could be found.

Within the body, hip implants are subjected both to mechanical and corrosive effects. In narrow crevices such as in the moving surfaces of modular femoral stems, even in the case of proven materials, complex interactions occur between mechanically and corrosively induced material damage, which can strongly influence the service reliability of the implant itself. After almost a year in service, the modular femoral stem presented in this article, fractured. The stem, which had been implanted into a somewhat less than active patient, fractured possibly as a result of defective implantation and diagnosed loosening, causing fretting and corrosion which eventually resulted in the fatigue fracture of the modular hip stem. The failure analysis presented, carried out as part of an IMWF student research project at the MPA University of Stuttgart, was initiated to investigate the damage found at a number of different levels and using various different investigatory techniques in order to determine the cause of the failure and to suggest guidelines to aid in the investigation of other similar failures.