The vacuum treatment with high pressure gas quenching involves quenching in a flow of inert gas in a pressure range between 1 bar and 12 bar with gas velocity after the austenitization phase. The nitrogen pressure, the speed of agitation and the type of flow are defined depending on the geometry and type of steel of the hardened component. The objective of the high pressure gas quenching process is to change the microstructure from austenite to martensite, thus obtaining the desired hardness increase with a number of advantages over traditional quenching. Gaseous quenching has additional advantages over liquid quenching:
- cleaning of the metal surfaces and hollow areas of the parts after the heat treatment
- ecological process (no disposal of oil, salt bath residues or detergent residues)
- high flexibility to control the intensity of cooling
- possibility of reducing heat treatment distortion
- elimination of microstructural defects such as IGO and NMTP
The solubilization treatment of stainless steels consists of an annealing treatment aimed at regenerating the austenitic grain in order to eliminate the effects of the cold rolling of previous processes or to re-establish the corrosion resistance characteristics.
The low pressure carburizing (LPC), also called vacuum carburizing, refers to the carburizing process that takes place at pressures below normal atmospheric pressure through the use of a pure hydrocarbon gas (acetylene) that releases the necessary carbon. The main advantages of low pressure carburizing are the total prevention of intergranular oxidation and uniformity of treatment in the event of complex geometries, in particular deep and narrow blind holes.
The SolNit® treatment is an enrichment treatment under vacuum used to harden the surface of both austenitic as well as martensitic stainless steels and ensure total hardening depths of 0.1 to 2.5 mm. In this way the resistance of the stainless steel can be increased by enriching the surface with atomic nitrogen at high temperature.
The hardening treatments by precipitation and ageing allow for the materials to be rendered more resistant through the controlled release of the constituents to form aggregates of precipitate that significantly increase the resistance of the component. Solubilization is typically performed at elevated temperatures in accordance with the material’s technical data sheets, followed by rapid cooling in gas to room temperature. Typically, the material should be cooled to a temperature of less than 90°F (or less, in some cases) prior to further ageing treatment.