PRODUCT MADE FROM AN ALLOY CONTAINING ONE OR MORE OF Cr, Al, Si, Ti, M AND SOCALLED ODE AND METHOD TO PRODUCE SAID PRODUCT

Abstract: The invention refers to a metallic product containing one or several of the metals chromium, aluminium, silicon, and/or titanium in such large amount that said metal or metals form a corrosion protective oxide layer on the metal surface in an oxidising atmosphere and a procedure to manufacture the product. The characteristic of the invention is that the metallic product at least in a layer next to the metal surface contains more than 0,5 weight ppm hydrogen and at the same time more than a total of 0,01 weight % of one or several of the elements that in their elementary form and/or as oxides have the ability to efficiently dissociate oxigen in the boundary between the oxide layer of the product and the surrounding gas phase, here referred to oxygen dissociating elements, ODE, and which belong to the following group of metals, that is rare earth metals, here referred to as REM, i.e. yttrium and elements with the atomic numbers 57-71, and scandium, hafnium, zirconium, niobium, tantalum, titanium, paladium, platinum, and rhodium.

Description: PRODUCT MADE FROM AN ALLOY CONTAINING ONE OR MORE OF Cr, AL Si, Ti, M AND SOCALLED ODE AND METHOD TO PEODUCE SAID PRODUCT FIELD OF THE INVENTION 5 The present invention relates to a metallic product of an alloy containing one or several of the metals chromium, aluminium, silicon and/or titanium in such amount that said metal or metals form a corrosion resistant layer on the surface of the metal product in oxidising atmospheres. The invention also relates to a method of manufacturing the 10 product and the use of the product in various applications. The invention is applicable particularly for heat resistant materials. Among these, heat resistant ferritic and austenitic stainless steels and other alloys, which normally contain high amounts of chromium and nickel, can be mentioned. Also silicon in significant 15 amount can be present in these types of stainless alloys. The metallic product according to the present invention can also be made of heating elements or materials for heating elements which can resist extremely high temperatures and which typically contain 20- 25% chromium and approximately 5% aluminium. Among aluminium alloyed materials also ferritic stainless steels, for example steel for catalytic combustion for automobiles 20 can be mentioned. Other possible applications are metallic products made of super alloys, alloys containing chromium as the main constituent, containing aluminium as the main constituent, and titanium based alloys or alloys which otherwise contain titanium in significant amounts. It should however be realised that the field of application of the present invention should not be limited to the specific types of materials mentioned, 25 which are only examples of a number of possible applications. BACKGROUND OF THE INVENTION It is known that the corrosion resistance of alloys mentioned above depends upon the ability of the material to form a thin, corrosion resistant oxide layer of chromium, silicon, 30 aluminium, and/or titanium oxide on the metal surface. It is however also known that the oxide layer generally does not produce a full protection due to the presence of microscopic pores and cracks in the oxide layer. In particular, when the metallic product, which is manufactured from the alloy, is exposed to high temperatures in oxidising environments, the defects in the oxide layer can lead to substantial oxidation of the metal. 35 It is also known that the growth and the adherence of the protective oxide layer are related to the transportation of metal ions out of the alloys. From SE 462 395 it is learnt that the addition of 0.01-0.15% rare earth metals to silicon alloyed, heat resistant austenitic materials, reduces spalling of oxide at high temperatures. The effect of cerium and other rare earth metals in the quantities mentioned in combina- tion with silicon has a positive influence on the growth of the protective SiO 2 layer on the metal surface, when it is exposed to high temperatures in oxidising environments, the SiO 2 layer which resists the transportation of metal ions, in particular chromium, out of the alloy, which reduces the spalling of the oxide. From SE 421 325 and SE 446 636 it is also learnt about adding of yttrium to chromium aluminium iron alloys and chromium aluminium silicon iron alloys intended for high temperature materials with good oxidation resistance. Any improvement of the oxidation resistance due to the yttrium addition has however not been reported in these documents. In SE 421 325 is however reported, with reference to GB 1 045 993, that alloys with less than 20 weight-% chromium and small amounts of yttrium lose their oxidation resistance. In SE 446 363 reference is made to US 3,027,252 according to which alloys of iron, chromium, aluminium, and yttrium exhibit high temperature resistance and good oxidation resistance. Hydrogen is normally looked upon as an impurity in alloys in general. In certain types of steels, hydrogen, which is dissolved in the molten steel, can cause cracks, so called flakes during the cooling down after hot working. In order to avoid this risk it is common practice that steels of this type are annealed for several days in order to eliminate the hydrogen. Hydrogen pick-up during pickling of steel in non-oxidising acids for instance could result in material fracturing at lower tension than what is normally the case. This is referred to as hydrogen embrittlement, and can be avoided by eliminating the hydrogen by heating of the material. It is also known that hydrogen decreases the oxidation resistance of alloys of the types mentioned above. For several reasons hydrogen is normally considered to be harmful and not to have any positive effects. As mentioned above, the corrosion resistance of materials of the kind indicated in the introduction, is dependent upon the presence of a corrosion resistant oxide layer on the metal surface, that the oxide layer has good adherence to the metal substrate and that it as far as possible is free from defects in the form of microscopic pores and/or cracks. It is assumed that the oxide growth at the interface between the metal and the oxide promotes the adherence of the oxide. In "Oxidation of Metals, Vol. 51, Nos. 3/4, 1999, Hydrogen in chromium: Influence on the High-Temperature Oxidation Kinetics in O 2 , Oxide- Growth Mechanisms, and Scale Adherence; B Tveten et al." is reported that the non- desired oxide growth at the oxide/gas-interface is dependent upon the transportation of cat-ions through the oxide layer, while the beneficial oxide growth at the metal/oxide- interface depends upon oxygen from diffusion or otherwise. In the referenced article it is also reported that hydrogen in the metal increases the transportation of metal but reduces the transportation of oxygen in the oxide layer and that hydrogen in this way worsens the corrosion resistance of the material in oxidising environments. DESCRIPTION OF THE INVENTION The basis for the invention is the surprising discovery that hydrogen in alloys of the type indicated above in combination with one or several of elements that in their elementary form and/or as oxides have the capability to efficiently dissociate oxygen at the interface between the oxide layer of the product and the surrounding gas phase, in this case referred to as "oxygen-dissociating elements", ODE, belonging to the following group of metals, rare earth metals, hear referred to as REM, i.e. yttrium and elements with the atomic number 57-71, and scandium, hafnium, zirconium, niobium, tantalum, titanium, palladium, platinum, and rhodium, appear to be beneficial in completion of the protective oxide layer, that is to contribute to making the oxide layer more dense by eliminating pores and other defects and/or improving the adherence of the oxide and thereby also improving the corrosion resistance of the material in oxidising environments. Furthermore a lower anodic dissolution in liquid chloride environment, which suggests improved corrosion resistance in liquid media containing chloride ions. In order to get a noticeable improvement the metallic product, at least in a layer next to the metal surface, approximately 1 mm thick, should contain more than 0.5 weight ppm hydrogen and at the same time more than a total of 0.01 weight % ODE. Preferably the hydrogen content in said surface layer should be at least 1 weight ppm, and more desirable at least 2 weight ppm, simultaneously in combination with at least 0.03 weight %, preferably at least 0.05 weight % ODE. In order to achieve the best effect said layer next to the metal surface of the metallic product should contain more than 5 weight ppm hydrogen and more than a total of 0.1 weight % ODE. Also higher levels of hydrogen and ODE are preferred, as indicated in the claims. In a preferred embodiment said ODE can be REM and any or some of the metals scandium, hafnium, palladium, platinum, and rhodium, or of basically only REM. Tests have shown that hydrogen in non-ODE alloyed materials of the kind mentioned in the introduction of this write-up worsens the oxidation resistance of the material at high temperature, that additions of ODE to non-hydrogen containing alloys of said type also worsens the oxidation resistance of the material at high temperature, that additions of both ODE and hydrogen to alloys of said type can improve the oxidation resistance of the material at high temperature, and in at least certain aggressive, liquid media, such as chloride containing liquids, that an optimum level of hydrogen can be found which gives the best oxidation resistance of ODE alloyed materials of said type at high temperature, but also that the optimum level of hydrogen depends on the content of the alloy and partly on the content of ODE, and partly on the oxide layer forming metals chromium, aluminium, silicon, and/or titanium. that the optimum level of hydrogen, giving the best oxidation resistance of ODE alloyed materials of said type can be determined by measuring the time to reach a certain level of oxygen pick-up in samples of varying hydrogen content in an oxidising environment at high temperature, and that significant improvement of the oxidation resistance also can be achieved at both lower as well as higher hydrogen content than the optimum hydrogen content of the alloy, i.e. within a hydrogen content range that includes the optimum hydrogen content of the alloy. From these observations can be concluded that the hydrogen content of the alloy according to the invention generally should fulfil the expression H^ - O. l x Hopt ≤ Hopt ≤ lO x Ho p t ^ H n And more desirable fulfil the expression Hmin — 0.3 X H t Hopt 3 X Hopt = H^, where H opt is the hydrogen content which in all alloys, within the framework of the composition relative to the metal elements stated in the claims, results in the longest time for a certain level of oxygen pick-up, when the material is exposed to an oxidising environment at high temperature, for example at some temperature in the range 800 to 1100°C. Most likely the level of hydrogen in at least said surface layer should be minimum 10 weight ppm, and preferably minimum 15 ppm more preferable minimum 20 ppm. In order to achieve a very high effect the alloy should probably contain more than 0.5 % ODE, and at least 0.8 % ODE. The maximum level of ODE depends to a certain degree upon whether the metallic product as a whole contains ODE, or whether ODE is only present in the surface layer. In the first case the level of ODE should amount to 3 % and in the latter case amount to maximum 10 %. In the first case ODE is added to the alloy in its molten state in the form of metal, for example yttrium or in the form of so called misch metal, basically containing cerium and lanthanum, and/or in the form of oxide, for example yttria, Y 2 O 3 , in an amount corresponding up to a level of maximum 3 weight % ODE. In the latter case the ODE can be applied directly onto the metal surface, in order to bring the surface layer to contain considerably higher amounts of ODE; up to a maximum of 70 weight % ODE. The application can be performed for example by brushing the ODE onto the surface together with an indifferent carrier or by dipping the product in a fluid medium containing ODE, followed by firing and/or drying. l^ in Tests performed have indicated that there is an optimum relation R πώ , between the level of hydrogen and the level of ODE, expressed as weight ppm H/weight % ODE, in the surface layer of the product in order to achieve the best corrosion resistance, and that the levels of hydrogen and ODE should be adjusted relative to each other in such a way that the relation between the level of hydrogen and ODE are R mύ , and maximum R^ x in accordance with the following expression: where Rπώ, is 3, preferably 10 and R^ x is 200, preferably 50. Hydrogen can be added to the alloy in its molten state, for example by injection of water vapour in connection with the metallurgical treatment of the melt. As an alternative, or preferably, the hydrogen is added to the metallic product in solid metal phase by diffusion of the hydrogen. In the case where the metallic product is a strip or a wire diffusion of hydrogen into the goods can be performed at raised temperature, for example at 900- 1200°C, preferably at 1050-1200°C, in a furnace filled with hydrogen gas, for example a furnace used for bright annealing, through which the strip, wire or corresponding is continuously guided. Moreover the alloy could be made in a conventional way by normal melting practice, cast, hot rolled etc. The alloy could also be made using powder metallurgy, by spray forming or by other in fact known technique. Also new known techniques are of course possible to use. BRIEF DESCRIPTION OF THE DRAWINGS In the following description of the tests performed reference will be made to the attached drawings, of which, Figure 1 is a diagram that shows the oxygen pick-up in samples of a commercial Fe, Cr, Ni, Si alloy containing 0.05 % Ce, as function of the time of exposure in a O 2 -H 2 O atmosphere at 900°C for different times of hydrogen pick-up of the samples. Figure 2 shows the framed area A in Figure 1 in larger scale. Figure 3 is a diagram, derived from Figure 2, which shows the time for pick-up of a certain amount of oxygen for the same samples as a function of the time for hydrogen pick-up of the samples. Figure 4 is a diagram that illustrates the oxidation kinetics at 20 mbar O 2 at 1000°C in a basically hydrogen free Fe, Cr, Al alloy with varying yttrium content. Figure 5 is a diagram that illustrates the oxidation kinetics at 20 mbar O 2 at 1000°C for a strip of a commercial Fe, Cr, Al alloy with different levels of hydrogen. Figure 6 is a diagram that in the same way as Figure 1 illustrates the oxidation of test pieces, in this case of a Fe, Cr, Al alloy containing 1 % Y at 20 mbar O + H 2 O for varying times of hydrogen pick-up. Figure 7 is a diagram, derived from Figure 6, that in the same way as Figure 3 shows the time for pick-up of a certain amount of oxygen as a function of the time for hydrogen pick-up. Figure 8 A-C shows the surface of test pieces, that have been exposed to hydrogen pickup for 0, 9 and 120 minutes respectively and evaluated according to Figures 6 and Figure 7, Figure 9 is a diagram that illustrates the oxidation in an oxidising atmosphere at 900 °C of test pieces of basically pure chromium with and without 1 % yttria respectively and with different levels of hydrogen. In all cases in this text and in the figures where no other reference is being made, reference is made to weight % and weight ppm. DESCRIPTION OF PERFORMED TESTS AND RESULTS ACHLENED TEST SERIES 1. The base material in this test series was a heat resistant , austenitic Fe, Cr, Νi alloy with the tradename Avesta 353MA ® with the nominal composition in weight % 0.05 C, 0.15 Ν, 25 Cr, 35 Νi, 1.3 Si, and 0.05 Ce, balance iron and impurities. From this alloy samples were made in the shape of 0.1 mm thick foils which were polished mechanically with SiC paper, 2400 mesh, after which the samples were rinsed in 99.5 % ethanol. The test pieces were exposed to hydrogen pick-up, i.e. were brought to pick up hydrogen by diffusion, to different degrees by being exposed to hydrogen pick-up for varying amounts of time. The hydrogen pick-up was performed by electrolysis at room temperature and atmospheric pressure with the test pieces immersed in the electrolyte, which consisted of water with the test piece as the cathodic electrode. The time for hydrogen pick-up for the different test pieces was 2, 8, 33, 115 and 350 minutes respectively. A test piece which had not been exposed to hydrogen pick-up, and which had a hydrogen level of < 1 ppm, was used as reference material. After exposure to hydrogen pick-up the test pieces were left to rest for some time to allow any hydrogen gradients in the test pieces to even out. The test pieces were then exposed to an oxidising atmosphere containing approximately 20 mbar O 2 + 2 mbar H 2 O at 900°C. The oxygen pick-up in the test pieces expressed as μmol O/cm 2 was registered after different times of exposure to the oxidising atmosphere. Figure 1 shows the oxygen pick-up expressed as μmol O/cm 2 as a function of the square root of time of exposure of the test pieces in the oxidising atmosphere. In Figure 2 an enlarged presentation is made of the framed section A of Figure 1. On the basis of this diagram the time for pick-up of 11.5 μmol O/cm 2 was estimated for each test piece. In Figure 3 this time is presented as a function of the time for hydrogen pick- up for the different test pieces. The time for pick-up of a certain amount of oxygen, in this case 11.5 μmol O/cm 2 represents a measurement of the corrosion resistance of the test piece in an oxidising environment; the longer time that is required for a particular level of oxygen pick-up the better the corrosion resistance. Thus, the best value with reference to the corrosion resistance was noted for the test piece that had been exposed to hydrogen pick-up for 115 minutes. Longer times of hydrogen pick-up made the corrosion resistance deteriorate. The worst oxidation resistance expressed as time for pick-up of 11.5 μmol O/cm 2 , 69 minutes, was shown by the test piece that had not been exposed to hydrogen pick-up, i.e. time for hydrogen pickup 0 minutes. The correspond- ing time for the best test piece, which had been exposed to hydrogen pick-up for 115 minutes was 89 minutes, corresponding to a prolongation of the time for oxygen pick-up of approximately 30 %. This first test series thus indicates that a certain improvement of the oxidation resistance can be achieved with the assistance of a certain amount of hydrogen in the steel, that an optimum with regard to the necessary hydrogen content to achieve the best corrosion resistance exists, but that the improvement of the corrosion resistance of this material containing 0.05 % Ce is relatively small at all hydrogen levels of the material. TEST SERIES 2. In this test series a FeCrAl alloy known under the trademark KANTHAL ® with the nominal base composition in weight % maximum 0.08 C, maximum 0.7 Si, maximum 0.4 Mn, 22 Cr, approximately 5 Al, balance iron and unavoidable impurities and with varying content of yttrium and hydrogen was tested. The test material was made up of 1 mm thick plates and 0.1 mm thick foils respectively. The test pieces were prepared in the same manner as in test series 1. At first the oxidation resistance of 1 mm thick samples with varying yttrium content, that is with 0.3 % Y, 1.26 % Y and with the basic alloy without yttrium and with low hydrogen content as reference material, were tested. After vacuum heating to 200-400°C and 3-4 minutes at 1000°C in vacuum the test pieces were exposed to oxidation at approximately 20 mbar O 2 at 1000°C. The oxygen pick-up was registered as a function of time in the oxidation chamber. The results are presented graphically in Figure 4. As can be seen in this diagram the oxidation increases drastically, i.e. the oxidation resistance deteriorates, with increasing yttrium content. The best corrosion resistance was shown by the samples that did not contain any yttrium. Thereafter 0.1 mm thick test pieces of the same base alloy without yttrium, both hydrogen free samples and samples with 40 ppm H, were tested. The oxidation was carried out under the same conditions as in the previous experiment. In this case, as it turned out, the reference material, which was hydrogen free, also in this case showed the best corrosion resistance. The material containing approximately 40 ppm H showed a considerably higher pick-up of oxygen, as can be seen in Figure 5. In the next test 0.1 mm thick test pieces of the same base material, containing 1 % Y were tested after varying times of exposure to hydrogen pick-up. The samples were exposed to oxidation in the same manner as the samples in test series 1. The oxygen pick-up after different times of treatment in the oxidising atmosphere was registered and is presented graphically in Figure 6. Thereafter the time consumption for a certain oxygen pick-up was calculated in the same fashion as in test series 1 for the test pieces exposed to variably long times of hydrogen pick-up, in this case an oxygen pick-up of 6.5 μmol O/cm 2 . The results are presented graphically in Figure 7. From the graph in Figure 7 it can be seen that the yttrium alloyed material exhibits a markedly improved oxidation resistance after a short time of exposure to hydrogen pickup, 9 minutes. At longer times of exposure to hydrogen pick-up the oxidation resistance decreased and after a very long time of exposure to hydrogen pick-up the oxidation resistance became worse than for material that had not been exposed to hydrogen pickup. The test shows that there is an optimum level, which is significant, giving the best result for an alloy with the above given basic composition, when the alloy contains 1 % Y. The faster pick-up of hydrogen, to reach the optimum level of hydrogen for the best corrosion resistance in the Fe, Cr, Al alloy compared with the Fe, Cr, Ni alloy (test series 1) can be a result of a lower diffusion rate of hydrogen in the previous alloy. The improvement expressed as time for pick-up of 6.5 μmol O/cm 2 amounted to approximately 650 % relative to the material that had not been exposed to hydrogen pick-up but which had been alloyed with yttrium. In Figure 8 A is a photograph which on a large scale shows the surface of the material that has not been exposed to hydrogen pick-up but instead has been degassed to a hydrogen level of less than 1 ppm. The oxidised material shows a number of defects in the form of pores in the surface layer, which explains the limited oxidation resistance of this material. Figure 8C shows in still higher magnification the surface of the material that has been exposed to hydrogen pick-up for the longest time, 120 minutes. On the surface of this material is thick oxide in the shape of isolated islands, with a thinner oxide exposed in between. This indicates that a high rate of transportation of metal in the oxides of the material that has the highest hydrogen content takes place and explains the deterioration of the oxidation resistance of this material compared with the material that has not been alloyed with hydrogen as well as with the material that has the best corrosion resistance. The latter, that has been exposed to hydrogen pick-up for 9 minutes, is shown in Figure 8B. This material shows a basically uninterrupted oxide layer without visible pores or other defects. TEST SERIES 3. In this test series powder metallurgically produced chromium was tested, and more specifically so-called Plansee chromium with and without yttrium in the form of 1 % Y 2 O 3 and varying levels of hydrogen. Test pieces were produced and treated in the same way as in test series 1. Exposure to hydrogen pick-up was performed in the same manner as in test series 1 and 2. The test pieces that had a thickness of 1 mm, were oxidised at 900°C at approximately 20 mbar O 2 + 2 mbar H 2 O. The oxygen pick-up at different times in the oxidising atmosphere was registered and is shown graphically in Figure 9. From the graphs in Figure 9 can be seen that the test pieces that did not contain yttrium as yttria but held significant amount of hydrogen, either from "natural" hydrogen pick-up from long time exposure in air or by four hours exposure to hydrogen pick-up, showed the worst oxidation resistance. The material that had not been alloyed with yttria and without hydrogen and the material that had been alloyed with yttria and without hydrogen showed the same tendency for oxygen pick-up. The material that had been alloyed with yttria and exposed to hydrogen pick-up for the longest time, 8 hours showed somewhat although not significantly better oxidation resistance. The lowest oxygen pick-up was shown by the yttria-alloyed material that had been exposed to hydrogen pick-up for 4 hours. From the results presented in Figure 9 also in this test series can be noticed that a combined positive effect can be achieved with relation to the corrosion resistance from the presence of a certain amount of yttrium and an optimum level of hydrogen. The hydrogen content of the material that had been exposed to hydrogen pick-up for 4 hours was measured to be approximately 25 ppm. Control weighing showed that the reference material which had not been exposed to hydrogen pick-up showed a 40 % larger weight increase compared with the material according to the invention that contained yttrium in the form of 1 % yttria and approximately 25 ppm hydrogen.

Claims: CLAIMS I. Metallic product of an alloy containing one or several of the metals chromium, aluminium, silicon, and/or titanium to such level that said metal or metals form a corrosion protective oxide layer in an oxidising atmosphere on the metal surface, characterised by that the metallic product at least in a layer next to the metal surface is comprising more than 0.5 weight ppm hydrogen and at the same time more than 0.01 weight % of one or several of the elements that has the ability to, in their elementary form and/or as oxides to efficiently dissociate oxygen in the boundary between the oxide layer of the product and the surrounding gas phase, here referred to as oxygen dissociating elements, ODE, and belonging to the following group of metals, that is rare earth metals, here referred to as REM, i.e. yttrium and the elements with the atomic numbers 57-71, and scandium, hafnium, zirconium, niobium, palladium, platinum and rhodium. 2. Metallic product in accordance with claim 1, characterised by the level of ODE in said surface layer being at least 0.03 weight %, and preferably at least 0.05 weight %. 3. Metallic product in accordance with claim 1 or claim 2 , characterised by the level of hydrogen in said surface layer being at least 1 weight ppm, and preferably at least 2 weight ppm. 4. Metallic product in accordance with any of the claims 1-3, characterised by the level of ODE being at least 0.1 weight %. 5. Metallic product in accordance with claim 3, characterised by the hydrogen level in said surface layer being at least 5 ppm, and preferably at least 10 weight ppm. 6. Metallic product in accordance with claim 5, characterised by the hydrogen content at least in a layer next to the metal surface being at least 15, and preferably 20 weight ppm. 7. Metallic product in accordance with any of the claims 1-6, characterised by the alloy containing at least 0.2 weight % ODE. 8. Metallic product in accordance with claim 7, characterised by the alloy containing at least 0.5 weight % ODE, and preferably at least 0.8 weight % ODE. 9. Metallic product in accordance with claim 8, characterised by said ODE basically being present only in a surface layer of the metallic product and the level of ODE in this surface layer being maximum 5-80 weight %. 10. Metallic product in accordance with any of the claims 1-8, characterised by said ODE being evenly distributed in the product and being present to a level of 3 weight %. I I. Metallic product in accordance with any of the claims 1-10, characterised by the hydrogen content of the alloy fulfils the expression H, = 0.1 x H opt < H opt < 10 x H opt = H max and preferably fulfils the expression Hπώ, = 0.3 x Ho P t ≤ Ho pt < 3 x Ho pt = H max , where H opt is the hydrogen content that in each alloy within the frame work for the composition with reference to the metal elements presented in claim 1 gives the longest time for a certain oxygen pick-up when the alloy is exposed to an oxidising environment at elevated temperature. 12. Metallic product in accordance with any of the claims 1-11, characterised by the ratio between the hydrogen content and the ODE content in said surface layer fulfilling the expression R πώ , < weight ppm H/ weight % ODE < R n , ax , where Rnώ, is 3, and preferably 10 and R max is 200, and preferably 50. 13. Metallic product in accordance with any of the claims 1-12, characterised by said ODE basically consisting of REM and/or any of the metals scandium, hafnium, palladium, platinum and rhodium. 14. Metallic product in accordance with claim 13, characterised by said ODE basically consisting of REM. 15. Method of producing a metallic product of an alloy containing one or several of the metals chromium, aluminium, silicon, and/or titanium in such large amount that said metal or metals form a corrosion protective oxide layer on the metal surface in an oxidising environment, characterised by the metallic product at least in a layer next to the metal surface is brought to contain more than 0.5 weight ppm hydrogen and at the same time more than a total of 0.01 weight % of one or several of the elements that in their elementary form and/or as oxides have the capability to efficiently dissociate oxygen in the boundary between the oxide layer of the product and the surrounding gas phase, here referred to as oxygen dissociating elements, ODE, and belonging to the following group of metals, that is rare earth metals, here referred to as REM, i.e. yttrium and the elements with the atomic numbers 57-71, and scandium, hafnium, zirconium, niobium, tantalum, titanium, palladium, platinum, and rhodium. 16. Method according to claim 15, characterised by the metallic product being brought to contain at least 1 ppm hydrogen, and preferably at least 2 ppm hydrogen. 17. Method according to the claims 15 and 16, characterised by the metallic product being brought to contain at least 0.1 % ODE in said surface layer. 18. Method according to claim 12, characterised by the metallic product being brought to contain at least 5 ppm, and preferably at least 10 ppm hydrogen. 19. Method according to claim 18, characterised by the metallic product being brought to contain at least 15 ppm hydrogen, and preferably at least 20 ppm hydrogen. 20. Method according to claim 17, characterised by the metallic product being brought to contain at least 0.2 % ODE. 21. Method according to claim 17-20, characterised by the metallic product being brought to contain at leastθ.5 % ODE, and preferably at least 0.8 % ODE in said surface layer. 22. Method according to claim 15-21, characterised by said ODE basically being added to the alloy in its molten condition. 23. Method according to claim 15-21, characterised by said ODE basically being added to a surface layer of the product by being applied onto the surface of the product and in this case to a level of 5-80 weight % on the surface. 24. Method according to claim 15-22, characterised by the hydrogen in said surface layer at least to a substantial part being added by diffusion into the material at elevated temperature, and preferably at a temperature in the range 900-1200°C. 25. Method according to claim 15-22, characterised by the hydrogen in said surface layer at least to a substantial part being added by electrochemical means, and preferably by cathodic polarisation/electrolytically in aqueous solution. 26. Method according to claim 15-25, characterised by added ODE basically being REM and/or any of the metals scandium, hafnium, palladium, platinum, and rhodium, and preferably basically only REM. 27. The use of a metallic product according to any of claim 1-14 as material being an electrical resistance material. 28. The use of a metallic product according to any of claim 1-14 as material being a carrier for a catalyst. 29. The use of a metallic product according to any of claim 1-14 as material being part of construction elements intended for use in oxidising environments at temperatures in excess of 400°C. 30. The use of a metallic product according to any of claim 1-14 as material being part of construction elements, containers or tubings designed for liquid media containing chloride or halogen ions.

Inventors: HULTQVIST GUNNAR, HULTQVIST, GUNNAR
Applicants: HULTQVIST GUNNAR, SANDVIK AB, HULTQVIST, GUNNAR, SANDVIK AKTIEBOLAG (PUBL)
Application year: 2000
Main classification: C22C38
IPC codes: B22D19, C22C1, C22C32, C22C38, C23C8