Development of high-strength P/M steels with optimized microstructure by new alloying and sintering techniques

Free nickel is avoided more and more in the development of new iron basis P/M alloys, either by complete elemination of free nickel or by using powders where nickel is already pre- or diffusion-alloyed with other elements. Beside this, the end product must fullfil at least the strength properties of conventionally used P/M steels. Within a collaborative project the prealloyed material Astaloy Mo(exp1) (Fe-1.5 per cent MO) was diffusion-alloyed with copper (nickel free) or with nickel, and finally mixed with carbon. Four new materials all in the density of rho = 7.4 g/cm3 were developed. These new developed materials and the high-strength alloy Distaloy AE + 1.0 per cent C as comparative basis were first investigated in the unnotched state (Kt = 1.0) under different stress-ratios (R = sigma min/sigma max= 0, -1, -2, -3). After finding out the most promising variants the investigations were continued with notched specimens (K(t) = 2.8) in order to evaluate the component related material behaviour. The research work is finalized by investigating an automotive part, an angle lever, with the best material state, in order to check the transferability of material data to components.