DE2322348C3 - Process for increasing the surface hardness of aluminum alloys - Google Patents

Description

characterized in that the substitution of certain parts of an otherwise

Aluminum alloys with a cyanide source in existing aluminum machines with heavier ones

a temperature of 450 to 550 ° C treated. Metals has at least two disadvantages.

2. The method as claimed in claim 1, characterized in that individual pieces of a machine can first be removed draws that a commercial alloy, be not inexpensive to manufacture, and an expensive one standing from the composition of the machine parts must be successful.

11 u- 11 o / cm · ^{On the} other hand, the machine becomes heavier the closer it is? f ^more aluminum replaced by heavier metals 0 8 b ^'S 13 ° / ν "kl ^a5 · S ^{enannter final} drawback is * · especially for n'e w λ \ ° / v aviation industry is crucial.
υ, 8 to 15 / Magnesium, Various studies are known regarding the • ' (° _T -j ^en> visibly the treatment of aluminum, but ^' ζ ° '^an> have not yet been directly related to the problem'? "/ Zi ^^ H ³ ° ^r ' ^cntet »to increase the surface hardness of aluminum alloy -" _,. Deodorant / αϊ · · rungs.

is treated. Rendus ", Vol. 198 (1934), pp. 1039-1041, an article

3. The method according to claim 1, characterized by the title "Sur la Nitruration de quelques Metaux" indicates that a commercially available alloy, made 35 by Paul L a f f i 11 e and Pierre Grandadam standing out published. A second article was published on August 1st

17 hi «10» / ς · ι · · 1936 by M. P. Läffi t te, M. M. E. E lc hard u s

η Rh- 1 1 "/ Τ) ^z f ' and P. G ra η dadam in the magazine" Revue de

0 8 to 13 ° / Nickel Industry Minerals "No. 375, p. 861, with the title

n'fi means λ \ ° / λΛαοηΛ-iim 4 ° »Recherches sur la Nitruration du Magnesim et de

<rO 7 ° / egg? ιL '.' Aluminum ', published. A third article was made

^ 'i ° . ^ ^en> in July and August 1935 in the journal »Ann. de

<0 2V Mangan Chimie «, 11th series, pp. 118 to 123, by Pierre Gran-

<02 / Zink und dadam under the title »Recherches Experimentales

na u- ono / Ai · ~ 45 sur l'Oxydation directe du Platine et Ia Nitruration de

76 to SU λ aluminum,. w. in ai »» - <τ ~ u · τ · ^

quelques Metaux "(Cu, Al, Mg, z.n, Fe, Ni, 1 u) treated will. public. In all three named publications

4. The method according to any one of claims 1 to 3, cures, the influence of nitrogen and Amd characterized in that a monia at high temperatures on a pure aluminum bath of 98% sodium cyanide and 2 % boron oxide ver 50 described as a cyanide source. In contrast, no one is turned on. Post a notice in these publications

5. The method according to claim 1 or 3, thereby cast aluminum alloys or cast and characterized in that the cyanide source is a melt of mechanically processed aluminum alloys or from 90% sodium cyanide, 3% sodium hydroxide, the use of cyanide ions mentioned.

1% sodium carbonate and 6% water related 55 From the German Degussa was in December

will. 1970 another publication with the title

6. The method according to any one of claims 1 to 5, »Wear-resistant surfaces due to the treatment characterized in that the treatment of components made of titanium and titanium alloys in the a period of 8 to 12 hours carried out salt bath "published by Bruno F i η η e i η. at will. 60 of this article are titanium or its alloys

with siale baths containing cyanide ions at a

Treated at a temperature of 800 ° C. Of course

The invention relates to a method for increasing can; Investigations with titanium under no circumstances

the surface hardness can be brought from cast or cast drawing to aluminum, and further

and machined aluminum alloys, is the use of temperatures in the range of 65

consisting of the 800 ° C resulting from claim 1 is not possible for aluminum alloys.

Alloying elements and their proportions. In addition, there are two other reasons why

The surface hardening of aluminum alloys of Degussa articles does not affect aluminum alloy

3 4

teaching related to learning. The Degussa- these particles contain Ni. The diffraction pattern and article do not indicate the composition of the bath; the data obtained from microsamples show it, but merely states that carbon and the presence of elemental silicon in the oxide nitrogen form mixed crystals with titanium, which is quite stratified. Evidence of the oxidation of either Si appears dubious. Rather, it is the view 5 or Ni were not found
of the inventor of this subject matter of the application that in practice the cast or cast and vanadium carbide and aluminum nitride are formed in part and that these compounds are responsible for the formation of a layer deep in the salt bath over the period of time. Degussa, however, found immersed, and after completing this process, that the composition of the layer was unknown. In the present case, the inventor also has to wash out water. Afterwards, tests were carried out to determine that silicon, magnesium and nickel did not adhere to the treated aluminum surfaces! are necessary. The differences in the treatment of led, namely according to the Vickers hardness test E: titanium and aluminum, consist essentially in 92-55 according to the edition of the ASTM standards of that the hard layer in aluminum is essentially 15 1955, part 1, ferrous metals which is formed by the American by alloy components inside the Aluminum Society for Testing Materials, Philadelphia, Race alloy, such as silicon, Street 1916, on pages 1694 to 1699, whereas the hard layer is a titanium alloy. The test is hereinafter referred to as Vickers by direct reaction between the bath and the hardness test. The amount of used Verder surface of the titanium alloy is generated. In the 20 search load was 35 g.

In the latter case, there appears to be no migration of parts. In preparation for the salt bath, it is useful to

to take place from the inside to the surface. Cyanide salt flux or other auxiliary agents.

In contrast, the invention is intended to mix in a mixture which makes it possible to pour the salt bath or by casting and mechanical machining at a temperature of 450 to 550 ° C aluminum alloy obtained with increased upper hold. Examples of such agents are surface hardness and a related method using boron oxide under a mixture of sweets will. trium hydroxide and sodium carbonate. These auxiliary

According to the invention, this is achieved in that the agents do not react, but enable them

the aluminum alloy of the type indicated with only that the cyanide ion in the appropriate form in the

a cyanide source at a temperature of 450 to 30 temperature of 450 to 550 ° C in contact with the

Treated at 55O ° C. Aluminum alloy is brought.

Appropriate further developments of the invention The theory of the method: Although by the

The other procedures do not result in any interpretation of the subject matter of the invention

Proverbs, way a limitation by a theoretical

The preferred heating time of 8 to 12 hours 35 would appear to include about half an hour of incubation time. that the phenomenon of surface hardness appear with times of more than 20 hours because of the migration of silicon from the inside to the superparabolic relationship of time and depth area is connected, with one of the layer behind the surface is not practical. Shorter treatment zone of lower silicon content remains. The times of about 4 hours brought good results. Mobility of the silicon atoms increases with the silicon and a small surface layer depth, but the calcium content up to a maximum of approximately the same hardness as with longer treatments 18% (e.g. alloy 138) . With further increase showed. Furthermore, the zone behind this layer is not deprived of the silicon content, as if it is completely saturated with silicon crystals. This, for example in the case of alloy 244 with a SiIi factor, is dependent on the hardness gradient from the cium content of about 24%. In addition to the silicon surface to the core and the anchoring of the upper migration, the hard surface layer seems to be significant in the matrix. To have Al ₃ Ni. Although the increase in hardness

There were experiments on the treated alloy mainly a consequence of the increase in silicon

carried out. To be a consideration of the micro content in the hard surface layer

The microstructure of the treated alloys shows that the 50 seems to have the hardness of the alloy Y of one

Growth of an oxide layer can be viewed simultaneously from the other point of view. the

winding of the layer consisting of hard particles silicon content of the y-alloy is only 0.5%, see above

he follows. that consequently no significant silicon migration

X-ray diffraction studies were given at the The hardness of the surface layer dei

The surface of the treated alloys 124 and 138 55 / alloy depends mainly on the formation of

accomplished. These showed that the surface of the MgAl ₂ O _{4 is} traced back, which is believed to be the

treated alloys with a spinel-like result of oxidation during the salt bath treatment

Oxide with a lattice parameter of 8.07 ± °, 2 Ä development.

was covered. The two components NiAl ₂ O ₄ apparently a combination of the concentric

(8.05 Å) and MgAl ₂ O ₄ (8.08 Å) are the main components of silicon and / or Al ₃ Ni on the surface

Sizes for these experimental data, however, showed elec- tricity as well as the formation of MgAl ₂ O ₄ occurrences, where

Electron micrographs that the oxide contains Mg. as a result of the treatment according to the invention di <

As a result, MgAI ₂ O _{4 is} the main component of surface hardness generated in the aluminum alloy

Oxide layer. This layer contains numerous metal-wills. In addition, others may not be known

lic particles that occur as Al ₃ Ni 65 effects through X-ray diffraction.

have been identified, with the X-ray diffraction in. As for wear resistance, the up is

Agreement with test results on micro-steps of different, different particles in de

Above arose from which it could be inferred that the hard layer was a very favorable phenomenon

Different hardness runs parallel to different elasticity, which creates the risk of brittle particles removed, decreased.

The oxide layer on the outermost outside has a different composition and consists essentially of MgAl ₂ O ₄ compared to the hard particle layer, which mainly consists of Si crystallites. An exposure time of only 4 hours produces layers of reduced thickness but practically the same hardness. It should be noted that the hardness is a property of the crystallites formed, while the thickness of the hard surface layer depends on the exposure time. The abrasion resistance, on the other hand, depends on two factors: increased hardness usually increases the abrasion resistance, and a greater thickness causes a longer abrasion time for the layer.

The oxide layer consists mainly of MgAl ₂ O ₄ . The oxide layer can contribute to the overall hardness, but its hardness is much lower than that of the Si layer. The hard layer consists of Si and some Al ₃ Ni. This Al ₃ Ni also has a lower hardness than the Si particles.

Even a short exposure time of 4 hours produces a hard layer of reduced thickness in alloys 124, H38 and 244.

The exposure time and temperature have some influence on the thickness of the hard layer. It a parabolic relationship between thickness and exposure time was found as follows:

p = K JV

ρ = thickness in 0.001 mm,

K = constant, changes slightly between

5 and 7,
/ = Time in hours.

Temperature 530 ° C, time 8 hours; Hard layer thickness = 18 μ.

Fig. 3:

Not Etched - 150 χ Alloy 124; Treatment: NaCN + 4% B ₂ O ₃ , temperature 530 ° C, time 12 hours; Hard layer thickness = 20 μ.

¹⁰ Fig. 4:

Alloy 138;

Not etched - 150 χ Treatment: NaCN 4 temperature 530 ° C. Time 4 hours; Hard layer thickness = 8 μ.

4% B ₂ O ₃ ,

25th

30th

Fig. 5:

Not Etched - 150 χ Alloy 138; Treatment: NaCN + 4% B ₂ O ₃ , temperature 530 ⁰ C, time 8 hours; Hard layer thickness = 15 μ.

Fi g. 6:

Not Etched - 150 χ Alloy 138; Treatment: NaCN + 4% B ₂ O ₃ , temperature 530 ⁰ C, time 12 hours; Hard layer thickness = 17 μ.

Fig. 7:

Not etched - 150 χ Alloy 244: Treatment: NaCN + 4% B ₂ O ₃ , temperature 530 ⁰ C, time 4 hours; Hard layer thickness = 12 μ.

35 Fig. 8:

The higher the temperature, the sooner a certain hardness appears to be obtained.

The actual hardness of the layer does not depend on the thickness. The hardness is based on the type of particle, be it that it consists of a magnesium-aluminum oxide complex or consists of silicon. The apparent hardness, however, shows higher values with increasing Thickness of the layer, which is a consequence of the penetration resistance which the pressure body at a given load is opposed.

Embodiments of the invention are provided below explained in more detail with reference to the drawing. It shows

F i g. 1 to 12 and 14, 16 photomicrographs of alloys treated according to the invention,

F i g. 13 and 15 photomicrographs of untreated alloys,

Fig. 17 and II! the relationship between layer thickness and exposure time,

F i g. Figure 19 shows the results of wear tests carried out on alloy 124.

The F i g. 1 to 16 are based on the following data:

F i g. 1:

Not Etched - 150 χ Alloy 124;
Treatment: NaCN ^ f- 4% B ₂ O ₃ ,
Temperature 53O ° C, time 4 hours;
Hard layer thickness = 13μ.

6o

Not etched - 150 χ
Treatment: NaCN I

Alloy 124;
4% ΒΛ.

Not Etched - 150 χ Alloy 244; Treatment: NaCN + 4% B ₂ O ₃ , temperature 530 ^° C., time 8 hours; Hard layer thickness = 14μ.

Fig. 9:

Not Etched - 150 χ Alloy 244; Treatment: NaCN + 4% B ₂ O ₃ , temperature 530 ° C, time 12 hours; Hard layer thickness = 25 μ.

Fig. 10:

Not Etched - 150 χ Alloy 244; Treatment: NaCN + 4% B ₂ O ₃ , temperature 520 ^° C., time 12 hours; Hard layer thickness = 10 μ.

Fig. 11:

Not Etched - 150 χ Alloy 124; Treatment: NaCN + 4% B ₂ O ₃ , temperature 520 ° C, time 12 hours; In this figure, the silicon migration surface of the test piece can be observed

Fig. 12:

Not Etched - 590 χ Alloy 124; Treatment: NaCN + 4% B ₂ O ₃ , temperature 530 ° C, time 12 hours; Micro hardness impression (35 g); Hardness of the matrix = 104 kgf / mm ² ; Hard layer hardness = 1200 kp / mm ² .

Fig. 15:

Alloy 124 X 120 - not etched; Condition: as cast.

Fig. 14:

Alloy 124 X 120 - not etched; Treatment conditions: bath 90% NaCN + 3% NaOH + 1% Na ₄ CO ₃ + 6% H ₂ O, temperature 540 ^° C., time 13 hours; Hard layer thickness = 15 μ.

Fig. 15:

Alloy 138 X 120 - not etched; Condition: as cast.

Fig. 16:

Alloy 138 X 120 - not etched; Treatment conditions: bath 90% NaCN + 3% NaOH + 1% Na ₂ CO ₃ + 6% H ₂ O,

Temperature 54O ⁰ C, time 9 hours;
Hard layer thickness = 6 μ.

The relationship between layer thickness and exposure time is shown in FIG. 17 and 18.

F i g. 19 shows the results of wear tests

with alloy 124. The friction test was carried out according to ASTM Publication D 2714-68.

The alloy 124, carried out on the friction tests

ίο had been treated for 4 hours at 540 ⁰ C in a bath with 49% NaCN, 49% KCN and 2% B ₂ O ₃ .

The following is a description of the preferred embodiments of the invention. All of the alloys used were cast or cast in sand or in permanent molds and machined.

Examples of the alloys used and the analysis of their components are given in the tables below refer to:

designation Alloy> ' <0.5 Alloy 124 Alloy 138 Alloy 244 Composition: 3.5 to 4.5 Si% 1.75 to 2.25 11 to 13 17 to 19 23 to 26 Cu% 1.25 to 1.75 0.8 to 1.5 0.8 to 1.3 1.0 to 1.7 Ni% <0.6 0.8 to 1.3 0.8 to 1.3 0.8 to 1.3 Mg% <0.2 0.8 to 1.3 0.8 to 1.3 0.5 to 1.0 Fe% <0.2 <0.7 <0.7 <0.7 Ti% <0.2 <0.2 <0.2 <0.2 Mn% - <0.2 <0.2 <0.2 Zn% 90 to 93 <0.2 <0.2 <0.2 Cr% - - 0.3 to 0.5 Al ⁰ Z 82 to 85 76 to 80 69 to 73

These alloys are known and are used as before or as in the table below on others Way designated.

designation

Alloy Y alloy 124

alloy 138

alloy 244

ASTM: B-108-55T US government designation Aluminum Association trade name S.A.E.

A.M.S.

DIN-1725 ALCAN NURAL DIN-1725

CN 42 A

OQ-A-1596b class

242

142 39 4222 (sand cast)

218 1761 SN 122 A

QQ-A-596b Class 9

A-332

A-132

321

G Al Si Cu Ni 11

6207

3210

G Al Si Cu Ni 11

616 5
1761 P

6166
2361

The above four kinds of alloys were subjected to cyanide ion by partial or complete immersion of the alloy into the corresponding salt bath over a period of 8 to 12 hours at a temperature of 500-530 ⁰ C. The specimen was then washed off with water and the hardness of the treated surface was determined at various points.

Examples.lto7

Examples of the salt baths used are given as follows:

Salt bath A:

98 percent by weight sodium cyanide and 2 percent by weight boron oxide (B ₂ O ₃ ).

Salt bath B:

90 percent by weight sodium cyanide, 3 percent by weight sodium hydroxide, 1 percent by weight sodium carbonate and 6 weight percent water vapor.

The results obtained with the treated alloys after washing with water are

609 609/301

given below using the Vickers hardness (HV) in kp / mm ^a . Aluminum alloy is 110 to 120 kp / mm ^a .

10

The hardness HV of the untreated egg

Surface hardness of treated aluminum alloys Vickers microhardness

example 2 3 4th 5 6th 7th 1 Alloy 124 Alloy 138 Alloy 244 Alloy Y Bad A Bad B Bad A Bad B Bad A Bad B Bad A Bad B HV (kp / mm ^s ) HVOcp / mm ¹ ) HVOcp / mm ¹ ) HV (kp / mm «) HV (l: p / mm ») HVOcp / mm ' HV (kp / mm ² ) HVOcp / mm «) 860 400 640 1200 510 400 560 760 540 360 1390 760 401 520 900 600 860 1150 260 940 540 680 950 260 500 ' 320 1100 320 820 1000 620 535 940 1100 480 1100 610 1400 1170 460 1380 1140 818 1200 510

In a further experiment, alloy 124 and alloy 138 were treated in the manner according to Examples 1 to 7 with a bath which had the following composition:

49 percent by weight sodium cyanide, 49 percent by weight potassium cyanide, 2 percent by weight boron oxide (B ₂ O ₃ ).

The Vickers hardness (HV) in kp / mm ² for Alloy 124 and Alloy 138 for 9 hours of treatment at 550 ° C is as follows:

35

Alloy 124

Alloy 138

580 670 1000 820 740 960 900 700 1010 630 800 970

In addition 8 sheets of drawings

dd

Claims (1)

ι 2 is undoubtedly an extremely desirable appearance. 1. Method for increasing the surface hardness use of a light metal, such as aluminum cast or cast and mechanically minium, then result when its hardness is so far wrought aluminum alloys consisting of 5 could increase that it can be used in areas _ _,. " _{ΛΟ / c} .... can, where previously heavier, but harder metals ü, 2 to 30.0 /, ijiüzium, ^ _{ß steel} ) _can be used. To get through the n'ok- ^S Ü'rw vt ^ l ^ 'relative softness of the aluminum resulting 0.2 to 6.0 / _o nickel, to overcome disadvantages, it has been customary to date w ^ J? £ magnesium, ίο places where the hardness or the surface resistance h ' ^S η! ί / τ · ^ω ' are critical, aluminum materials by others h ' ^S isvif ^taa ' to replace metallic materials. This is how posts become h ' ^S \ n ° / 7- ^a P ^gai1 ' significant wear or abrasion in machine h ^'S invrh parts of other metals manufactured as aluminum, j η Γι · - ^m is whereas the other parts of many machines are off and the remainder aluminum, consist of aluminum.