The history of Distaloy

Abstract

The low alloy steel powder Distaloy, is today widely used in applications demanding high strength and wear resistance. Its basic properties and composition were designed half a century ago in the USA. The advantage lay in the fact that it was a partial prealloy, i.e. the alloying elements – copper, nickel and molybdenum – were bonded in particulate form to the basic iron particles, thus avoiding impairment of the compressibility. By balancing the contents of nickel and copper it was possible to minimize dimensional change on sintering. Bonding the alloy particles to the iron particles minimised segregation and also contributed to dimensional stability. Carbon was added conventionally as fine graphite. However, the new powder, marketed as Ancoloy, did not take off in North America, due to the lack of suitable applications, the cost of the alloying elements and – above all – the poor compressibility and high oxygen content of the iron powder then available. The high, variable oxygen content made it impossible to control the carbon content with the precision necessary to achieve the desired strength and hardness.

In the 1960s, demand for high strength precision parts emerged in the European car industry, initially at Citroen, which pioneered increased use of PM parts in European cars. The component was (and still is) the synchronising hub used in manual transmissions. Höganäs had in the mid-1960s developed a sponge iron powder with much higher compressibility, and this was taken as a raw material for an improved grade, later to be called Distaloy SA. This new powder had improved compressibility and very low oxygen and carbon contents, which made it possible to make the high strength precision parts that the car industry required. Distaloy was immediately accepted and used, first in the French car industry, then elsewhere in Europe and subsequently also in Japan. Some years later, when high compressibility atomised powder became available, the same basic technique was applied to these, to produce the Distaloy A grades, which now are most popular. Höganäs continues to improve and refine the production techniques and to come up with compositions for new applications.

The properties and the metallurgy of Distaloy-based materials have been thoroughly studied by metallurgists at Höganäs and at PM laboratories throughout the world, and new results are still being reported with respect to both applications and fundamental properties. A parameter of great relevance is of course the cost of raw materials and much effort is going into finding more cost effective ways of achieving the desired results.