Manganese assisted pack boriding of sintered steels

Pack boriding of powder metallurgy steels in a powder mixture consisting of ferroboran, carbon ferromanganese and alumina without halides was investig ated. Fe-C and low alloy Fe-Ni-Mo-(Cu)-C steel tensile bars were sintered a t 1120 degreesC for 1h in cracked ammonia and then pack borided at 1050 deg reesC for 2h. This boriding treatment resulted in the formation of hard sur face layers and also in an increase in tensile strength, which was further- enhanced by subsequent heat treatment. In parallel, increases in hardness a nd density were noted with the formation of a new microstructure in the sam ple core-an enhanced postsintering effect. It is concluded that the boridin g powder mix used was effective for the pack boriding of powder metallurgy steels.