Page 54 - Zmist-n2-2015

Ô³çèêî-õ³ì³÷íà ìåõàí³êà ìàòåð³àë³â. – 2015. – ¹ 2. – Physicochemical Mechanics of Materials

FATIGUE OF SINTERED POROUS MATERIALS BASED
ON 316L STAINLESS STEEL UNDER UNIAXIAL LOADING

A. FALKOWSKA, A. SEWERYN
Bialystok University of Technology, Poland
The paper presents the results of fatigue tests of sintered porous 316L austenitic stainless
steel with different porosity. An analysis was conducted into the parameters obtained from
the hysteresis loop in the load cycle (changes in the value of Young’s modulus, maximum
and minimum stress). Fatigue life of the porous material of varying density according to
the relationship Manson–Coffin was determined.
Keywords: metallurgy powder, fatigue, porous materials, 316L stainless steel.

The mechanical properties of sintered porous 316L austenitic stainless steel have also
been the subject of research in recent years. However, these materials take into account the
results of high density (porosity of the order of several percent), while it would also be
desirable to define the mechanical properties of low density agglomerates [1, 2].
There is a certain group of publications on the preliminary study of fatigue life of
sintered porous 316L steel. These works present the fatigue life of 316L steel in com-
parison to the stability of other biomaterials used in implants. These results are rather
qualitative than quantitative [3]. Some publications show the obtained values of selec-
ted strength parameters such as compressive strength and Young’s modulus, though
these results are incomplete [4–6]. There is only a few publications which present a
quantitative analysis of crack propagation, but they use the finite element simulation
only. That kind of model is used primarily to determine the effect of size, the size or
the distance between the pores [7, 8]. The test results, which could describe the mecha-
nism of formation and development of defects in the material on the basis of which it
would be possible to propose the computational model, hence allowing the prediction
of the state of material damage and fatigue life, are still missing [9].
The aim of this study was to develop a methodology and implementation of expe-
rimental strength and fatigue life of sintered 316L stainless steel, and consequently
obtain fatigue characteristics for different degrees of material porosity. These characte-
ristics form the basis for the development of computing, based on fatigue life, to be
used in the engineering practice.
Experimental fatigue testing of sintered samples of 316L stainless steel. Test
specimens made of sintered 316L stainless steel were created in the multistage powder
metallurgy process. The powder with a grain size of 125…250 mm was cold-pressed in
a matrix on a specially constructed testing machine EDZ-100. Numerous solutions
have an innovative nature, due to the fact that their use was assigned exclusively to the
needs of this research. The sintered samples with three degrees of porosity 41, 33 and
26% were used in this test. Prepared compacts were sintered for 1 hour in an oven with
a vacuum device at a temperature of 1230°C. Following this process, the samples were
exposed to the last stage of the preparation process, which gave the final shape by
cutting with water and machining.

Corresponding author: A. FALKOWSKA, e-mail: a.falkowska@pb.edu.pl
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