A 12 pct Cr martensitic/ferritic steel was designed and produced to study Laves and Z-phase as precipitation hardening particles under creep conditions (650 °C). According to thermodynamic calculations, W and Cu additions were selected to ensure the precipitation of Laves after tempering. It is known that Z-phase formation does not follow the classical nucleation theory. Indeed, MX particles are transformed into Z-phase by Cr diffusion from the matrix to the precipitate. Therefore, to promote fast Z-phase formation, Ta, Co, and N additions were used to produce Ta-MX, which will be transformed into Z-phase. The main result achieved was the precipitation of Laves after tempering, with a particle size of 196 nm. As regards to Z-phase, the transformation of Ta-MX into Z-phase after tempering was confirmed by the formation of hybrid nanoparticles of 30 nm. Although W and Ta have a low diffusion in the martensitic/ferritic matrix, characterization of the precipitates after isothermal aging revealed that Laves and Z-phase have fast growth kinetics, reaching 400 and 143 nm, respectively, at 8760 hours. Consequently, creep test at 650 °C showed premature failures after few thousand hours. Therefore, it is expected that future research in the field of martensitic/ferritic steels will focus on the growth and coarsening behavior of Laves and Z-phase.

The stress behavior and the associated microstructure evolution of industrial Ti(C,N)/α-Al₂O₃ coatings subjected to thermal cycling are investigated by in situ energy dispersive synchrotron X-ray diffraction and transmission electron microscopy. Temperature-dependent stresses and changes in microstructural parameters (domain size and microstrain) are analyzed by in situ measurements at different temperatures between 25 and 800 °C, both in the heating up and cooling down step, including several thermal cycles. Transmission electron microscopy is used to evaluate defects before and after the thermal treatment. The introduction of high compressive stresses in α-Al₂O₃ by top-blasting is connected to a high defect density at the basal planes of the alumina layer. The stress relaxation of the alumina layer at high temperatures is associated with a successive annihilation of defects until a reversible temperature-dependent stress condition is set. Top-blasting does not change the initial microstructure and residual stress of the Ti(C,N) layer. Ti(C,N) shows a cyclic stress behavior associated with the heat treatment and an elastic deformation behavior in the temperature range investigated.

We investigated the stress behaviour of Ti(C,N) coatings deposited on WC-Co substrates during an individual thermal cycle. The stress analyses were performed in-situ by energy dispersive X-ray diffraction using a white synchrotron beam. The stresses were determined using the sin²ψ method combined with scattering vector measurements at the strain-free ψ-tilt, in order to avoid the effect of the chemical C/N gradient on the strain distributions over sin²ψ. It was found that compressive stresses induced by top blasting on the coating are released after the individual thermal cycle. During heating and cooling, part of the Ti(C,N) coating was oxidized into a TiO₂ rutile phase. Stress analysis was also performed in this phase in order to evaluate the influence of oxidation on the residual stress of the coating. The obtained results can support the design of coated tools with improved properties at interrupted cutting operations by understanding the role of thermal cycling on the stresses of Ti(C,N) coatings.