High Strength Powder Metallurgy Materials

Abstract

The main factors controlling the mechanical properties and
dimensional stability of sintered iron base alloys are discussed
in detail in the literature review of this thesis. From this,
the need to examine in detail the iron-carbon-copper-nickel system
is established. In order to clarify the industrial aspects of
the project, the review also contains a description of the basic
stages in the ferrous powder metallurgy process, and is concluded
with a cost analysis containing a detailed breakdown of the costs
involved in producing a component by the powder metallurgy route
and by machining from bar stock.

The experimental work was planned statistically, using a
factorial design. The object was to determine the significance
of the effect of alloy composition and as-pressed density on the
strength and dimensional stability of sintered iron-carbon-copper-
nickel alloys, prepared from pre-mixed elemental powders.
The magnitude of the significant effects has also been determined
using multiple regression analysis.

The importance of as-pressed density in determining mechanical
properties, is confirmed. A number of main effects and
interactions between variables, particularly between alloying
elements, appear to have a significant effect on strength and
dimensional stability during sintering. The multiple regression
equations obtained are complex since they contain a number of
interaction terms and the magnitude of the effect of each variable,
particularly alloying elements, is highly dependent on the levels of the other variables. A second regression analysis
was made using the results obtained from alloys of "commercial
significance’. Thus, the highly alloyed materials were excluded
on the basis of poor properties and expense.

Mechanisms involved in strengthening and dimensional control
are briefly discussed to illustrate that there is some agreement
between the effects observed from this investigation and those
proposed in published literature.

Date of Award	1972
Original language	English