Recent Advances in Heat-Treat Technology

In the last ten to fifteen years, heat treating techno-logy has witnessed a lot of advances. The introduction of new alloys, like duplex stainless steel, micro- alloyed steel, HSLA steels, low-cobalt maraging steels, austempered ductile iron, directionally solidified and single crystal superalloys, aluminium-lithium alloys, various metal matrix composites etc., have called for new heat treatments based on structure-property corre-lations. There have also been changes in heat treatment processes, including improvements in continuous annealing, induction heating, and surface hardening operations using laser or electron beams, establishment of the commer-cial viability of plasma-assisted case-hardening processes, and advances in thermo-mechanical processing. However, the most dramatic advances have taken place in the area of newly developed tools for improving process character-ization and process control. Notable amongst such devel-opments are the improved instrumentation for controlling furnace temperature, furnace atmosphere, and surface carbon content, the practical application of statistical process control (SPC), the application of computer mode-lling for prediction of hardness profiles, quantitative modelling of tempered on case hardened properties, and the computer-assisted object oriented selection of materials and their heat treatment processing. Many of the advances listed above are being covered in some of the other lect-ures in this workshop. A selection of the items mentioned above are discussed in a general manner in this paper