A 42SiCr experimental steel was heat treated by the quenching and partitioning (Q&P) heat treatment to achieve a combination of high strength and ductility. The associated microstructure is characterized by finely distributed martensite laths with a small volume fraction of retained austenite embedded.

The goal of this work is to provide a comprehensive characterization of the mechanical properties of all subzones in the heat-affected zone (HAZ) of welded 42SiCr-Q&P steel. In order to achieve this, dedicated micro-specimens were produced by subjecting material samples to a specifically selected thermal cycle in a dilatometer.

Afterwards, the specimens were characterized by mechanical testing and microstructural assessment. One specimen series is dedicated to the assessment of the mechanical properties of the material after welding, another four specimen series represent some carefully selected strategies to mitigate adverse effects of welding.

Tensile testing revealed a decrease in yield strength in the HAZ by 35% max. The ductility of the material showed inverse behaviour. Material in the supercritical zone shows >2000 MPa of ultimate strenght, but at the same time is very brittle. The most remarkable result showed, that the  embrittled material in the supercritical zone can be successfully transformed by holding the material at temperatures in the range of 200-250 °C for 5 minutes upon cooling leading to a yield strength of around 1400 MPa along with a ductility of >10%, successfully restoring the desired property combination. This very promising observation, gives rise to interesting perspectives on the matter of heat management during welding of 42SiCr-Q&P.