This paper reports on a study to investigate the creation of a mixed microstructure consisting of proeutectoid ferrite, bainite, and austenite in a medium carbon high silicon steel. The microstructure was produced through the use of a continuous cooling process at a moderate cooling rate from the austenitizing temperature range to room temperature. The investigation also examined the influence of this microstructure on the mechanical properties of the material. Test results indicate that the developed steel has better mechanical properties compared to commercially available dual phase steels.

Several case studies are presented illustrating issues that may be encountered when developing induction heat treating processes. The relationship of how induction heat treating parameters affect the metallurgy of production parts is examined in the form of case studies. These include the importance of normalized versus anneal starting microstructure as it relates to the ability of pearlite to transform to martensite within the short induction hardening process window. The influence of a non-uniform microstructure with proeutectoid grain boundary ferrite is discussed as it relates to prior structure. A team approach to balancing design specification with manufacturing cost and sound metallurgical practice is covered for an AISI 1060 steel channel component with complex inductor design. Another case study addresses how evaluating hardness in the as-quenched versus tempered condition can provide additional detail relating to back tempering in tooth by tooth hardened gears. The final example is the influence of frequency of case depth formation for an AISI 4140 cross roller section.

Quench cracks became a challenge in large serial production of martensitic components. The geometry is simple, and concentrations of stresses from the geometry itself were not indicated by numerical simulation. Grain boundary ferrite is presented in the component surface from where the cracks start. An example from another application is interesting to consider; titanium grade 5. Grain boundary alpha on prior beta grain boundaries is not accepted for aerospace applications. The volume for plastic deformation in the phases along the grain boundaries is restricted. The ductile part of the fracture indicates forces from unbalanced quenching and elevated temperature at time of crack start. The general focus for improvement will be overcritical surface temperature, vapor phase break and mix of turbulent/lamellar flow. More effective quenching around the whole component is, in this case, assumed to be better than slower quenching.

Controlled gaseous nitriding of ternary Fe-Cr-Mo alloys leads to the development of ternary, mixed nitrides in the ferrite matrix, which show complex chemical, structural, and morphological transformations as a function of nitriding time: initially continuous precipitation of fine, coherent, cubic, NaCl-type (Cr,Mo)N x nitride platelets develop, which later transform to a novel, hexagonal CrMoN 2 nitride by a discontinuous precipitation reaction. Some relatively coarse cubic nitrides also occur in the ferrite lamellae. The Fe-Cr-Mo alloys with varying Cr/Mo ratio, but all containing a total alloying element (Cr+Mo) content of 2 at.%, showed similar kinetics of continuous precipitation of cubic (Cr,Mo)N x nitride. The kinetics of the discontinuous precipitation reaction is faster for the alloys with lower Cr/Mo ratio.