DE1219234B - Corrosion-resistant cobalt-chromium-tungsten hard alloys with high wear resistance - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C22c

German class: 40 b - 19/02

Number: 1219 234

File number: B 75234 VI a / 40 b

Filing date: January 30, 1964

Opening day: June 16, 1966

Highly wear-resistant and heat-resistant cobalt-chromium-tungsten hard alloys with a relatively high proportion of carbon consist in the as-cast state, as well as as weld metal, essentially from one large amount of hard chromium-tungsten carbides, which are converted into a conversion-free, face-centered cubic, tough cobalt-chrome matrix are embedded. The interaction of hard carbides and tough basic mass causes the properties of these alloys of high wear resistance and heat resistance. The two main structural components are also important for corrosion resistance authoritative. The carbides are only slightly attacked by hydrochloric acid and sulfuric acid, but they are Cobalt-chrome matrix. To the extent that the basic mass is removed from the structure, the carbide network also loses its cohesion and can easily be removed mechanically replace the not yet attacked core. An improvement the corrosion resistance can therefore only be achieved by improving the resistance of the Reach the basic mass in which the carbides are embedded.

The invention now relates to cobalt-chromium-tungsten hard alloys high wear resistance,

Corrosion-resistant cobalt-chromium-tungsten hard alloys with high wear resistance

Applicant:

Gebr. Böhler & Co. Aktiengesellschaft, Vienna;
Branch: Gebr. Böhler & Co.
Aktiengesellschaft Vienna,
Büderich sales office

Named as inventor:

Dipl.-Phys. Dr. rer. nat. Anton Bäumel,

Lank (Ndrh.)

Claimed priority:

Austria from June 4, 1963 (A 4457/63)

which by alloying copper and possibly molybdenum a significantly better corrosion resistance exhibit. Two alloys with the following composition were melted:

Table 1

Chemical composition in% of cobalt-chromium-tungsten hard alloys with and without copper and molybdenum

alloy
No. C. Si Mn Cr W. CO (D Mon Cu Fe 1
2 2.2
2.2 0.15
0.17 0.22
0.17 30.3
30.3 20.3
19.0 38.4
40.9 3.0 2.0 8.8
2.3

(i) Calculated as the remainder.

From Table 2 it can be seen that the corrosion resistance by the addition of copper and Molybdenum is significantly improved.

Table 2

Weight loss in g / m ² h in hydrochloric acid and sulfuric acid of the two cobalt-chromium-tungsten hard alloys given in Table 1

alloy

No.

2
1

10% hydrochloric acid

Room temperature

6th
0.9

Boiling temperature

1120
250

20% sulfuric acid

Room temperature

5.2
1.0

Boiling temperature

430
4.3 The weight loss of the molybdenum- and copper-containing alloy is around five times smaller than that of the molybdenum- and copper-free alloy at room temperature. In the boiling sulfuric acid, it is particularly evident that the combined presence of copper and molybdenum results in an approximately 100-fold reduction in weight loss.

By electrochemical measurements on these alloys in 1 η-sulfuric acid at room temperature was also able to confirm the improving effect of copper and molybdenum on the corrosion behavior will.

To determine whether a further increase due to higher additions of copper and molybdenum the corrosion resistance can be achieved

609 579/320

a number of alloys were melted, the composition of which is shown in Table 3 is. ■ · · -,

TabeUe3

Chemical composition in% of cobalt-chromium-tungsten ^ hard alloys; .
with copper and molybdenum ■. *. .

alloy
No. ^: i; e. . ^; Si: l · Mr: - Cr W. Co (i) Mon Cu Fe 3 2.5 0.54 0.27 31.9 13.4 46.4 3.5 1.5 4th 2.3 0.55 0.33 31.0 18.8 41.4 3.4 2.3 0.0 5 2.5 0.47 0.24 31.6 13.0 42.9 3.1 4.1 2.1 6th 2.3 0.49 0.25 31.7 13.3 39.8 4.8 5.5 1.9-. 7th 2.3 0.49 0.26 31.7 14.0 39.8 6.7 3.4 1.4

AlsvRest. Calculated.

In order for the addition of copper and molybdenum To have a greater leeway in these melts compared to those in Table 1 cited the. ..Tungsten content. from 20% up around "13%. The, cobalt content in the alloys were each dimensioned in such a way that

that the iron content does not rise significantly above 2%. . .- ". '■ -.;.

Table 4 shows the weight losses in 10% Hydrochloric acid and 20% sulfuric acid, at room and boiling temperature for the items listed in Table 3 Alloys reproduced:

Tabel

Weight loss in g / m ² h in hydrochloric acid and sulfuric acid in Table 3. '".."'
specified cobalt-chrome-Wolfranv hard alloys in the cast and welded state

Salary Mon /, Gu lOige hydrochloric acid ge Boiling temperature ge r ■ ge Boiling temperature ge. Alloy -
No. - 3.5 Room temperature welds welds iOtyoige sulfuric acid welds welds 3.4 2.3 0.9 poured - 255 ' Room temperature 1.5 ^: poured 1.7 ti 4.1; poured; 0.8 258 257 0.03 7.6 - 2.4 3 4.8 5.5 0.6 0.7 234 310 poured 0.2 6.0: 9.4 ': 4th 6.7 3.4 1.2. 0.9 211 234 0.08 0.4 2.2 5, -3 - ■■■■ - ,: ₅ - ■■ -., ■ - '0.7 0.7 212 • 229 0; 02 : Ό, 3 4.7 4.2 ■ 'β 1.4 - 207 0.13 / ■ 3.8 7th • 3.2 0.02 0.04

The weight losses of these alloys were recorded on both the welding rods and those made from them Weld quality samples determined. Table 5 contains the under corresponding conditions Weld metal specimens of common Kbbalt-Chrom-

Tungsten hard alloys determined weight loss. A comparison of the weight losses in Tables 4 and 5 "shows the superiority of the copper or copper-molybdenum-containing alloys compared to the 'common "alloys."

TabeUe5

Chemical composition in% and weight loss in g / m ² h in hydrochloric acid
⁼ Chemical composition in% and weight loss in g / m ² h in hydrochloric acid

2.57 . Mn. Cr. . W. Cq (I) B. Nb 30.3 lOVoige Boil _r 20 per cent Boiling, 0.65 0.6 hydrochloric acid tempe sulfuric acid tempe-. C. 0.34 0.9 space rature space rature 0.8 0.1 , 27.9 5.6 31.8 0.9 tempe 2900 tempe 113 0.5 0.04- 24.6 13.5 58.5 -: -,. <2.0 rature 1231 rature 178 .-. 1.74, 0.04 31.1 18.5 46.5 - 33.5 1411 " 71.0 146 2.15 0.1 24.3- 4.6 67.9 - 4.3 861 . 12.8 ' 188- 2.62 0.12 29.0 19.0 43.0 0.65 2.5 "■, 3.7 1352. 20.0. 188 1.37 3.5 18.2 .2.4 2.9 16.3

From Table 4 it can also be seen that the 65 hold on to these elements. The most suitable addition alloys 6 and 7 with the highest levels of cobalt-chromium-wohram-hard-copper composition and molybdenum no higher resistance alloy with high wear resistance and increased than <Me, alloys 4 and 5 with lower Ge corrosion resistance, especially to

Sulfuric acid and similar, not too pronounced reducing media, should therefore be within The following limits are: 2.2 to 2.5% carbon, 30 to 32% chromium, 13 to 20% tungsten, 39 to 47% cobalt, up to 1% each manganese and silicon, more than 0 to 6% copper, possibly up to 6% Molybdenum.

The following alloy composition has proven to be particularly favorable: 2.0% carbon, <Ξ 1% Silicon, <Ξ 1% manganese, 30% chromium, 14% tungsten, 46% cobalt, 4% molybdenum, 2% copper.

The attack of acids on the alloys takes place in such a way that initially the basic material is dissolved out and the carbide remains as a relatively adherent coating on the sample. But since this is Jr simultaneous exposure to corrosion and wear from the workpiece in question the mechanically removable carbide coating must also be taken into account when determining the weight loss will. Therefore, before the weight loss determination, the carbide residue was always checked with a Steel wire brush removed. The weight losses determined afterwards are therefore higher than when the Carbide coating is left on the samples.

Such as residue isolation and X-ray fine structure examinations show, the addition of copper and molybdenum does not change either the amount or the type the precipitated carbides noticeably influenced. The added copper and molybdenum mainly accumulate in the matrix and affects its resistance to corrosion.

An impairment of the wear resistance and the heat resistance is due to the addition of Copper and molybdenum not to be expected. The Rockwell hardnesses of the alloys listed in Table 3 are between 52 and 60 Re. The hardness values increase as the copper and molybdenum content increases.

It is also known that by adding up to 4% molybdenum in cobalt-chromium-tungsten hard alloys whose hot hardness is improved, so that two essential improvements are made by molybdenum Alloy properties is achieved.

Claims (2)

Patent claims: 1. Corrosion-resistant cobalt-chromium-tungsten hard alloys with high wear resistance 2.2 to 2.5% carbon, 30 to 32% chromium, 13 to 20% tungsten, 39 to 47% cobalt and up to 1% each of manganese and silicon, characterized in that they contain more than 0 to 6% Contains copper and possibly up to 6% molybdenum. 2. cobalt-chromium-tungsten hard alloy according to claim 1, characterized in that it consists of 2.2% carbon, 30% chromium, 14% tungsten, 4% molybdenum, 2% copper and up to 1% each Manganese and silicon, the remainder being cobalt. 609S79 / 320 6.66 © Bundesdruckerei Berlin