THE EFFECTS OF CORROSION ENDURANCE OF DIFFERENT HEAT
TREATMENTS FOR IRON BASED POWDER MATERIALS
Uğur ÇAVDAR*, Enver ATİK*
*CBÜ Makine mühendisliği Bölümü, Mühendislik Fakültesi, Muradiye Kampüs, MANİSA/TÜRKİYE
ABSTRACT:
For the machine parts which were produced by powder metallurgy method were expected endurance to the
corrosion. For this purpose the samples which were prepared iron based powder metal were formed %2, %3
ratio ( for weight ) of Cu and %0,2, %0,4, %0,6, %0,8 ratio of (for weight ) graphite. 8 different powder metal
sample group are produced. %0,8 ratio of Zn Streat were used as lubricant while samples were produced.
Samples were pressed by one axis hydraulic press even as 500Mpa pressure. Dimension of the samples were
10x10x55mm. Samples were sintered at 1120°C for 30 minutes and then applied boronizing, steaming and
carbonitriding treatments. The effects of corrosion endurance were compared with these treatments.
Keywords: Iron based powder, boronizing, steaming, carbonitriding, corrosion.
1.
INTRODUCTION
If we want to say simply what is the powder metallurgy, is materials forming technique [1].
Corrosion of metal is a chemical or electrochemical process in which surface atoms of a solid metal react with a
substance in contact with the exposed surface. Usually the corroding medium is a liquid substance, but gases an
devein solids can also act as corroding media. In some instances, the corrodent is a bulk fluid; in others it is a
film, droplets, or a substance adsorbed on or absorbed in other substance [2,3].
A wide array of experimental techniques is currently being used to assess the corrosion resistance of PM alloys.
These tests range from simple laboratory exposure studies in open containers to more sophisticated
electrochemical approaches aimed at gaining insight into the underlying mechanism of PM alloy corrosion. This
section introduces the more commonly employed tests and provides specific examples of the use of these
methods in evaluating the corrosion resistance of PM steels [2,4].
Exposure tests are commonly employed for reacing the performance of a group of related alloys and assessing
quality control. Ideally, these tests should be conducted in actual service environments. Unfortunately, very few
references in the literature cite service or environmental exposure test results for PM materials; instead, much of
the PM litarure cites results from immersion and salt-spray cabinet testing [2,5].
2.
MATERIAL AND METHOD
The samples used in tests are produced by iron based powder metals. Iron, graphite, copper and
aluminum powders were used in these iron based powder metal samples. iron based powder metal were formed
%2, %3 ratio ( for weight ) of Cu and %0,2, %0,4, %0,6, %0,8 ratio of (for weight ) graphite. 8 different powder
metal sample group were produced. %0,8 ratio of Zn Streat were used as lubricant while samples were produced.
Numbers were given to these samples:
Table 1. % Ratios of the iron based powders.
Based of samples
Samples
%Cupper
1
2
2
2
3
2
4
2
5
3
6
3
7
3
8
3
9
2
10
2
11
2
12
2
13
3
14
3
15
3
16
3
% Graphite
0,2
0,4
0,6
0,8
0,2
0,4
0,6
0,8
0,2
0,4
0,6
0,8
0,2
0,4
0,6
0,8
% Zinc striate
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
% Aluminum
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
% Iron
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
Remaining
The powder metal used in the tests were ASC10029 that produced by Hougenas. (The characteristics are
shown at Table 1) It was mixed 20 minutes in 25 d/min. to have a homogeneous mixture. The samples were the
size of 10x10x55 mm and weight of 37 gr. The powder metal samples were gotten by milling in 600MP pressure
with one axis press.
Table 2. The characteristics of metal powder [1]
SPECIFICATION
MİN
RESULT %
MAX
GRANULOMETRY
B.S.S. MESH
MICRONS
85
180
0.0
0.0
100
150
0.5
0.3
150
106
12.5
200
74
19.1
300
53
19.8
350
45
11.6
-350
45
PHYSICAL PROPERTIES
30.0
40.0
36.7
Apparent Densty
g/cc
Flow
secs
2.55
2.75
2.69
30
26
CHEMICAL ANALYSIS
Copper
%
Oxygen
%
99.00
99.74
0.15
Table 3. The physical properties and chemical analyses of copper powders [1].
Micron
%
>180
0,0
>150
0,3
>106
12,5
>74
19,1
>53
19,8
>45
11,6
<45
36,7
Physical properties
Densty
2,69 g/cc
Fluidity
26s
Chemical analysis
Copper %
99,74
Oxygen %
0,08
Table 4. The Chemical analysis and screen analysis of copper powders [1].
Chemical Analysis
Test results
Dampless
0,05%
Ash
3,2%
C
96,8%
S
0,07%
Physical properties
+100 Micron
0,005%
Under to 10%
2,5 micron
Under to 50%
5,9 micron
Under to 90%
11,1 micron
Under to 99,99%
17,4 micron
0.08
Powder samples were sintered in classical sintering furnace. The sintering temperature is 1120°C in the classical
sintering process. The sintering process was performed in 30 minutes. The sample’s heat was degreed as
1120°C. Then 3 kinds of heat treatments applied 16 differed PM samples. These treatments were boronizing,
steaming and carbonitriding treatments.
Carbonitriding is a high temperature modified carburization treatment in an ammonia based atmosphere that
promotes both carbon and nitrogen diffusion into the component surface for hardening, usually followed by
quenching [6]. In this study carbonitriding was appied at 800 °C, 30 minutes to the iron based samples. Cooling
process was done at 80°C with martempering oils.
Steam treatments is a heat treatment typically above 500°C in an atmosphere containing steam, used to grow a
blue-black Fe3O4 tenacious surface oxide on steels [6]. Steam a treatment was applied to the iron based samples
in Toz Metal A.Ş. with same temperature in an inert gases atmosphere.
Boronizing treatment was applied to the samples at 950°C, for four hours into the boronizing cup. Ekabor© 2
was used for making boronizing treatment. Samples were boronized in a 40x40x110mm cup.
The prepare solution which include % 10 acid. These solutions aim was tested the samples endurance of
corrosion. The acid of H2SO4 was used for making corrosive environment. The samples weights were measured
before and after corrosion tests. While applying the corrosion test to the samples, samples were waited in the
solution for four hours. Samples were kept in the furnace about 30 minutes at 100°C for eliminating absorbed
acid.
3. RESULTS AND DISCUSSION
3.1. Hardness of carbonitriding.
Figure of sample
Figure 1. Taken hardness ponits are shown in the samples.
Figure 2. Measuring ponits of hardness and handness figure of carbonitriding samples (Without Al powder).
Figure 3. Measuring ponits of hardness and handness figure of carbonitriding samples (With Al powder).
3.2. Hardness of steaming.
Figure 4. Measuring ponits of hardness and handness figure of steaming samples (Without Al powder).
Figure 5. Measuring ponits of hardness and handness figure of steaming samples (With Al powder).
3.3. Hardness of boroning.
Figure 6. Measuring ponits of hardness and handness figure of boronizing samples (Without Al powder).
Figure 7. Measuring ponits of hardness and handness figure of boronizing samples (With Al powder).
3.4. Corrosion results of heat treatments of PM.
Figure 8. Carboniriding applied PM samples, weigth losses figure.
Figure 9. Steaming applied PM samples, weigth losses figure.
Figure 10. Boronizing applied PM samples, weigth losses figure.
4. CONCLUSIONS
In this study iron based powders are considered. Generally iron based powders are used in machine parts
which including %2-3 cupper, % 0,2-0,4-0,6-0,8 graphite and %0-1 aluminum, were applied boronizing,
steaming, carbonitriding heat treatments. This treatments hardness and corrosion results were investigated.
Streaming treatments’ hardness and surface hardness were seen least value to compare to the other heat
treatments. The high values of the hardness and surface hardness were seen at the boronizing samples.
Carbonitriding samples hardness and surface hardness values were between boronizing and streaming
values. Aluminum wasn’t so changed values of the hardness
After the corrosion tests most losing weights were seen carbonitriding samples. Minimum losing weights
were seen boronizing samples. Streaming samples values of weights lose were between carbonitriding and
boronizing values. At the corrosion test carbonitriding samples which were included %1 aluminum increase
the weight losses but included %1 aluminum was decrease weight losses of boronizing and streaming
samples.
Machine parts which are produce by powder metallurgy suggested to apply boronizing, steaming,
carbonitriding heat treatments which are increased the hardness and/or corrosion endurance after sintering
values of products.
SPECIAL THANKS
To Prof. Dr. Cevdet Meriç ([email protected]) and Prof. Dr. Haldun KARACA ([email protected] )
for their academic helps,
To Tozmetal Inc. (http://www.tozmetal.com/english.htm ), Aytaç Ataç ([email protected]) for their help as
the provider of the metal powders,
5. REFERENCES
1. J. R. Moon, “Introduction to PM”, A residentail training course for young materials / design engineers, 2008
Course figures Vol 1, EPMA, p.p. 3, Acqui Terme, Italy, 21st-29th June 2008.
2. Powder metallurgy training course 2008, organised by the european powder metallurgy association, p.p. 47,
23th-24th June 2008 Politecnico di Torino, Sede Di Alessandria, Italy.
3. Forms of Mechanically assisted degradation, corrosion: Fundementals, testing and protection, vol. 13A of
ASM Handbook, ASM International, 1987.
4. C. Molins, J.A. Bas, J. Planas, S.A. Ames, PM Stainless steaal: types and their characteristics and
applications, and. İn PM and partic. Mater., vol5, J.M. Capus, ed., plenum pres, 1992, p.p.345-357.
5. D.W. Yuan, J.R. Spirko, H.I. Sanderow, Colormetric corrosion testing of PM stainless steel, Int. J. Powder
metal.,p.p. 33, 1997.
6. German, R.M., “Powder Metallurgy Science”, MPIF, p.p. 349, USA, (1984).