Abstract
Quench hardening aims at the microstructural transformation of steels in order to improve hardness and mechanical strength. The aim phase is, in most cases, the martensite. It is necessary to heat the material until it obtains its austenitization and quenching by immersion in a fluid. Currently, it is common to use watery polymeric solutions in this procedure. These fluids, which are the mixture of polymers in water, vary their thermal exchange capacity depending on the concentrations applied. The increase in concentration minimizes the removal of heat from the part, reducing the formation capacity of martensite, and developing a lower hardness and strong steel. In this work, microstructural characteristics and properties of AISI 1045 steel quenched in solutions based on polyvinylpyrrolidone (PVP) in 10, 15, 20, and 25% concentration were evaluated. The microstructural characterization quantified the percentage of the phases in each concentration, demonstrating a reduction of martensite as the concentrations were high. The investigation of the samples by x-ray diffraction confirmed the absence of austenite retained in the material. Furthermore, a microhardness scale between the core and the surface was constructed, in which a reduction gradient of the indices of this property towards the core of the sample was evidenced.
Highlights
Resulting in residual stresses after the process end
The gradual transition between the first two phases of quench hardening, steam film, and boiling causes non-uniform elevation of the crystalline network because the microstructure of the lower sample turns into martensite first than the rest, increasing the magnitude of residual stresses
The aqueous polymer solutions are homogeneous mixtures of polymers dissolved in water
Summary
Resulting in residual stresses after the process end. Besides, the gradual transition between the first two phases of quench hardening, steam film, and boiling causes non-uniform elevation of the crystalline network because the microstructure of the lower sample turns into martensite first than the rest, increasing the magnitude of residual stresses. Polymers that do not present average solubility in water present a gradient of polymer concentration towards the interface between liquid and vapor In these situations, the rupture of the steam film is sudden, causing the extraction of more uniform heat, which is followed by boiling, initiated by the base of the s pecimen[8,9]. The film becomes more unstable and is more quickly extinguished When it cooled, the mixture becomes homogeneous again, but a thin layer of PVP remains attached to the sample, making it difficult to change the heat and extending the boiling and convection p hases[11,12]. Even if it is not in an expressive quantity, some of the austenite may be retained in the p rocess[15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
