Volume 7, Issue 2 (2007)                   Modares Mechanical Engineering 2007, 7(2): 1-15 | Back to browse issues page

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Hardfacing of H11 (1.2343) Hot Work Tool Steel With the Superalloy Stellite 6. Modares Mechanical Engineering. 2007; 7 (2) :1-15
URL: http://mme.modares.ac.ir/article-15-6479-en.html
Abstract:   (4696 Views)
Thermal fatigue (heat checking), mechanical fatigue, wear and plastic deformation of critical areas of hot forging dies at working temperatures are the main mechanisms that reduce their lifetime. During forging processes the surfaces of the dies reach temperatures of 700-800 ºC. Therefore, hardfacing of these areas with nonferrous elevated temperature hardfacing alloys such as Stellite 6 can improve the performance and lifetime of the dies, many times. Hot hardness, galling resistance, hot corrosion and oxidation resistance, adhesive wear resistance, low friction coefficient and absence of allotropic transformation up to 1100 ºC are the most important properties of Stellite 6. H11 tool steel is widely used as hot forging die material. This steel because of its high alloy contents and, therefore, its hardenability is very sensitive to high cooling rates involved during welding cycles and hydrogen induced cracking (HIC). For this reason, in this research hardfacing parameters of H11 tool steel with Stellite 6 in TIG welding method have been investigated. According to the results, hardfacing of this steel in annealed hardfaced condition isn't feasible and it is recommended that preheating and intermediate temperatures during the hardfacing cycle between 310-370 ºC. The suitable current for TIG hardfacing of this steel by φ3.2mm filler rod was determined to be 80-85 amperes for the first layer and 90-100 amperes for upper layers. The minimum thickness for obtaining maximum hardness in the hardfacing layer (41-42 HRC) under these conditions was determined to be 3mm. It is recommended that the effective heat input for hardfacing of this steel under three-body heat transfer conditions would be less than 455kJ/m. It is also recommended that the Δt8→5 of H11 tool steel hardfacing cycle would be in the range 6 to 15.3s. Finally it is recommended that H11 hardfaced tool steel would be stress relived in the range 425 -500 ºC for 1 hour per 30mm base metal thickness.
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Received: 2003/09/15 | Accepted: 2006/04/26 | Published: 2007/08/28

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