Papers by Author: Jan K. Solberg

Abstract: Shielded Active Gas Forge Welding (SAG-FW) is a solid state bonding process in which two mating surfaces are locally heated and forged together to form a bond. SAG-FW has so far mainly been used to join materials for pipe-line and casing applications. The present study has been conducted on an API 5CT L80 grade material in a prototype forge welding machine. Small-scale pipe specimens have been extracted from the wall of the production casing. The SAG-FW process is completed within a few seconds of heating and forging followed by controlled cooling. The microstructure of the weld is determined by the processing parameters. In this paper, microstructure results for SAG-FW processed L80 material have been obtained for a range of cooling rates and systematically compared with microhardness values. Microstructure observations at different regions of the weld have been made. Faster heating rate and controlled cooling resulted in a mixture of non equilibrium microstructures, but satisfactory mechanical properties have been obtained for optimized processing parameters.

Abstract: In this paper, new steel matrix composites have been developed by powder metallurgy/HIP and abrasive wear and aluminum sticking resistance of the materials have been investigated. The microstructure examination showed that Co-coated WC reinforcement was partly dissolved in a high speed steel (HSS) matrix and an interface layer of M6C formed, but both Co-coated WC and NbC reinforcements were stable in a high vanadium tool steel (CPM10V) matrix. The NbC reinforcement was also stable in a HSS matrix at the same HIP parameters. Property test results indicate that Co-coated WC-reinforced composites have higher abrasion resistance than the composites with NbC, but the latter possess the lowest aluminum sticking propensity. Compared with unreinforced alloys, abrasion wear resistance of the composites was increased by a factor of 3 to 10, most for the HSS-matrix composites.