Heat Treatment and Mechanical Testing of AISI H11 Steel

Abstract

Belonging to the class of chromium tool steels, AISI H11 possesses very good toughness and hardness, and is therefore suitable for hot metalforming jobs performed at very high loads. Mostly used in fabrication of helicopter rotor blades, H11 also has great potential as a die steel in hot-work forging and extrusion. This alloy steel can be heat treated to increase the service life and dimensional accuracy of the die and tooling. Main aim of the current investigation was to formulate an optimum heat treatment strategy for H11 steel, especially for hot work applications. High-speed milling and electric discharge machining were used to fabricate samples for tensile and impact testing. After various types of heat treatment (annealing, austenitizing, air cooling or oil quenching, single and double tempering), these samples were tested for hardness, toughness (impact), yield strength, tensile strength, and ductility. Microstructural analysis was also performed to analyze the effect of heat treatment on mechanical properties. As tempering temperature increases, hardness initially increases and then starts to gradually decrease; impact strength first decreases and then increases; and yield strength exhibits a fluctuating pattern of initial decline followed by an increase and another decrease. Even though H11 steel is highly suitable for both hot and cold-work, it is surprisingly not a common choice for metalworking dies and tools. Results presented here can encourage die designers and hot-work practitioners to explore the versatility of this tool steel, and to adopt appropriate heat treatment strategies for different applications.

Effect of Heat Treatment Processes on Metals and Alloys-A Review

“…Material is heated near to its critical temperature, hold/soaked at that temperature for 1 to 2 hours and then slowly cooled in furnace to the room temperature. The basic purpose of this process is to relieve internal stresses; refine grain structure, increase ductility and machining ability [6].…”

Tribomechanical Behaviour of TiAlN and CrAlN Coatings Deposited onto AISI H11 with Different Pre-Treatments

“…The wear resulting from the contact between the tool and the workpiece represents a major challenge. In order to increase the service life of tools manufactured using AISI H11, heat treatment and nitriding processes have been the most traditional approaches to reduce wear on the components [2][3][4][5]. With the introduction and industrial massification of protective nitride coatings, an additional overlay process has been proposed for the wear protection of sliding components.…”

Phase Transformations and Crack Initiation in a High-Chromium Cast Steel Under Hot Compression Tests

“…The final properties of the material are promoted by the subsequent heat treatments following the casting route, which allow the formation of a martensitic matrix containing uniformly distributed secondary carbides that yield to enhanced hardness ( Ref 4,7,8). Though work rolls for the roughing mill are massive parts weighing up to 40 tons, the heat treatment that follows the casting route must be handled carefully, while considering moderated heating and cooling rates in order to avoid distortions or detrimental residual stresses (Ref 9).…”