Stainless steel is one of the most widely used materials in todays industrial world. Its highly durable, low-maintenance and corrosion-resistant properties make it a highly desirable metal for many applications. In order to maintain and maximize these properties, it is necessary to heat treat the steel in order to achieve optimum hardness and increase its strength.
Heat treating stainless steel is carried out by both hardening and tempering processes. Hardening is a process which increases hardness and strength by subjecting the material to a temperature above its transformation range. The alloy of 1.25Cr-0.4W-18Cr-4V (1270°C) is designed to be hardened by heating to 1270°C and then cooling with oil, allowing tremendous structural hardness properties.
Tempering, on the other hand, involves cooling the material in order to reduce hardness and improve ductility. The 1.25Cr-0.4W-18Cr-4V alloy is designed to be tempered following the hardening process. This is done by reheating the steel to a temperature of 560°C, then allowing it to cool slowly in air. The temperature is important during the tempering process, as it affects the properties of the steel and also the microstructure which can be seen through a metallographic analysis
Temperature is a important consideration when it comes to heat treating stainless steels. By varying the temperature, strength, ductility, hardenability and corrosion resistance can be both increased and decreased. Hardening and tempering processes must be carefully controlled to ensure desired results. This is especially true for the 1.25Cr-0.4W-18Cr-4V alloy, as the materials microstructure is sensitive to the hardening and tempering temperatures.
The metallographic analysis of an alloyed 1.25Cr-0.4W-18Cr-4V sample, which has been heated and cooled according to the standard hardening and tempering processes, reveals a fine microstructure consisting of martensite and a trace amount of ferrite grains. The size of the martensitic grains is very fine and its morphology is uniform. This is indicative of successful hardening and tempering, indicating that the material was heated and cooled within the desired temperature range.
The addition of chromium increases the corrosion resistance of this steel alloy, while the addition of tungsten and vanadium helps to improve the hardenability and tempering behaviour of the alloy. This combined with the hardening and tempering process creates a strong, resilient material that is highly resistant to oxidation, abrasion and mechanical damage. This makes it an ideal material for applications requiring high strength and corrosion resistance.
By using the standard hardening and tempering process for the 1.25Cr-0.4W-18Cr-4V alloy, a material that is resistant to corrosion and highly durable can be obtained. The metallographic analysis of the sample revealed a fine microstructure, indicating that the material was heated and cooled within the desired temperature range. The addition of chromium, tungsten and vanadium also contribute to the corrosion resistance and hardenability properties of this alloy, making it a popular choice for many industrial applications.
