Title

TOUGHNESS OF 8% Cr COLD WORK TOOL STEELS AFTER VACUUM HEAT TREATING

TOUGHNESS OF 8% Cr COLD WORK TOOL STEELS AFTER VACUUM HEAT TREATING

Authorship

Arieta, Francisco; Silva, Douglas P; Netto, Eliana B.M.; Pannes, W K; Ernst, Claudia

DOI

10.5151/2594-5327-0454

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Abstract

An AISI D2 Steel, an 8%Cr – 2,75%V P/M steel and various new generation of 8%Cr ledeburitic steels have been vacuum heat-treated together at an austentizing temperature of 1030oC, followed by a sub-zero treatment and three tempers of 02 hours each at 520oC, resulting in a 58-62 HRC hadness range, typical for applications of such steels. The toughness of steels have been evaluated via impact tests with un-notched samples. The as-annealed and tempered microstructures have evaluated via optical microscopy. The results have shown that no relationship between hardness and impact values could be found among the investigated steels instead, the chemistry and microstructures differences, in particular volume fraction and size of primary carbides played the important role to explained the impact values differences among the steels. The P/M steel with its much finer and homogeneously distributed VC primary carbides, showed much superior impact values than all ledeburitic and ingot cast steels. Among the latter, the best results were achieved with an 8%Cr with aproximately 1%C, 1.4 %Mo and 1.8V, continuously cast which showed the lowest volume fraction of small primary carbides .

 

An AISI D2 Steel, an 8%Cr – 2,75%V P/M steel and various new generation of 8%Cr ledeburitic steels have been vacuum heat-treated together at an austentizing temperature of 1030oC, followed by a sub-zero treatment and three tempers of 02 hours each at 520oC, resulting in a 58-62 HRC hadness range, typical for applications of such steels. The toughness of steels have been evaluated via impact tests with un-notched samples. The as-annealed and tempered microstructures have evaluated via optical microscopy. The results have shown that no relationship between hardness and impact values could be found among the investigated steels instead, the chemistry and microstructures differences, in particular volume fraction and size of primary carbides played the important role to explained the impact values differences among the steels. The P/M steel with its much finer and homogeneously distributed VC primary carbides, showed much superior impact values than all ledeburitic and ingot cast steels. Among the latter, the best results were achieved with an 8%Cr with aproximately 1%C, 1.4 %Mo and 1.8V, continuously cast which showed the lowest volume fraction of small primary carbides .

Keywords

8% Cr; Tool steel; Toughness

8% Cr; Tool steel; Toughness