Influence of die wall lubrication on tensile properties of high temperature sintered and sinterhardened low alloy steel

The influence of die wall lubrication on the green strength and the tensile properties of a 1.5%Mo and 0.5%C steel, both as sintered and sinterhardened at 1250°C was investigated. Samples compacted using die wall lubrication had green strengths more than 100% higher than samples compacted at the same pressure using bulk lubrication, and a sintered density up to 98% of the pore-free ones may be achieved, compared to a maximum of 95% with bulk lubrication. Pore morphology and the matrix microstructure and microhardness were not affected. The tensile properties of both sintered and sinterhardened materials were much better for die wall lubrication than for bulk lubrication. Tensile strength increased up to 20%, tensile elongation up to 60%. The effectiveness of the system that delivers the lubricant on the die wall surface every stroke was verified successfully in the production of tensile specimens that do not have an axisymmetric geometry.