T 0486/14 17-05-2018

1. Main request - inventive step

1.1 It was not contested by the parties that starting from D4 as the most promising starting point for considering inventive step, the subject-matter of claim 1 differs herefrom by the feature

"a heating rate in the range of from 16.1°C (29 degrees Fahrenheit) per minute to approximately 22.2°C (40 degrees Fahrenheit) per minute"

The Board also finds no reason to disagree with this. D4 discloses in paragraph [0016] a pre-weld heat treatment for the alloy IN939 with a heating rate of 27.8°C ("50 degrees Fahrenheit") per minute, i.e. above the claimed range.

1.2 Paragraphs [0018] and [0019] of the patent explain that during exposure to the intermediate temperature range of from 593°C to 891°C, additional grains are created through solid state precipitation and that this precipitation changes the crystallography thus causing aging strains, possibly leading to strain age cracking prior to welding as the component is heated and cooled (see patent on column 4, lines 45-46 and column 5, lines 13 and 16-19). The turbine engine component to be repaired should therefore stay for as short a time as possible within this precipitation temperature range in order to minimize the occurrence of strain age cracking prior to welding. Paragraph [0019] then states that the component should not be within this range "for more than 17 minutes, preferably less than 13 minutes", which would lead to heating rates of more than 17.5°C and preferably more 22.9°C per minute, respectively. Paragraph [0019] does not disclose any reason or effect as to why the heating range should have an upper limit, instead teaching the skilled person that the heating rate should be as high as possible and preferably even higher than the claimed upper limit of the heating rate. The skilled person thus does not recognize in this paragraph, or from any other passage in the whole content of the patent, any effect of setting an upper limitation at 22.2°C per minute. Based therefore on the patent itself, this upper limit is not disclosed as anything but an arbitrary value that does not lead to any technical effect.

1.3 The respondent's argument that the objective technical problem was to increase high temperature ductility and weldability is not accepted by the Board. As explained in paragraph [0020] of the patent and in D8 in the passage bridging pages 2179 and 2180, it is the slow cooling rate and not the fast heating rate that allows more time for the gamma' precipitation to occur and for the gamma' particles to grow resulting in an increased high temperature ductility. This will ultimately reduce the likelihood of cracking during welding (as evident from the patent on column 5, lines 24-25 and column 6, lines 2-4, as well as D8, page 2180, last line) which is a different effect than the one provided by a fast heating rate.

Paragraph [0021] of the patent also explains that the increase in the number and size of gamma' particles shown in Figures 1B and 2B in relation to Figures 1A and 2A, respectively, is a consequence of slow cooling rates. Even if the changes in the gamma' particles (consequently increasing high temperature ductility) could be attributed to the heat treatment as a whole and to the heating rate range, as the respondent argued, all the detailed embodiments and photomicrographic inspection results of the patent relate to WASPALOY, and there is no information on file to make it credible that such an upper limitation in the heating rate would also lead to an increase in high temperature ductility for other nickel-based superalloys (i.e. over the whole breadth of the claim). Paragraph [0031] states only generally that the invention could be used with other alloys and does not provide any concrete information that could support the respondent's allegation that the effect is also present in other alloys. Also D4, paragraph [0014], confirms that some degree of adaptation is required for the invention to work with other nickel base superalloys.

1.4 Thus, whilst it is true that both the heating rate and the cooling rate have ultimately an effect on weldability, the rates provide different effects that lead to different objective technical problems - the heating rate affects cracking before welding whilst the cooling rate will affect cracking during welding. Moreover, as discussed above, the claimed upper limit to the heating rate is an arbitrary value which has not been demonstrated to provide any effect over the prior art. In this case, the Board does not find that it is appropriate to generalize the formulation to a common technical problem (such as "to improve weldability") to encompass the effects of features that are already known from the prior art. The drafting of the technical problem should be derived only from the effect provided by the differing feature over the whole scope of the claim.

1.5 As explained under item 1.2, in the present case there is no effect in setting an upper limit to the heating rate, since any heating rate that would minimize the time within the precipitation range would work. Thus, the upper limitation must be regarded as arbitrary, and the formulation of the technical problem can thus only be seen as being to provide an alternative heating rate suitable to minimize strain age cracking before welding.

1.6 The skilled person faced with this technical problem would look into D8, since D8 also deals with the improvement of the heat treatments of alloys. Table 3 discloses several pre-weld treatments applied to nine different sample groups. In these nine different samples only two different heating rates have been used: 10°C per minute for sample 7 and 20°C per minute for all the others.

D8, page 2182, 1st paragraph, discloses the results of sample group 7, where cracks were observed, and gives rise to the possibility that such cracks might be due to "the longer exposures of the samples in the temperature range of precipitation". Since for the preferred sample group 6, where only the heating rate was increased, these cracks were not present and in the remaining sample groups other parameter changes explained the cracks, the skilled person would learn from D8 that a heating rate of 20°C per minute is perfectly suitable to provide a short enough exposure to the precipitation temperature range and avoid strain age cracking before the welding operation for the alloy Rene 41.

However, since D4 already teaches in paragraph [0014] that, generally, the teaching of D4 can be used also with other nickel-based alloys such as Rene 41, the skilled person recognizes (when looking for alternative heating rates to adapt the method of D4 from paragraph [0016] as suggested in the paragraph itself) that methods for Rene 41 would also come into question. The skilled person would thus recognize that the value of 20°C per minute used in D8 is perfectly suitable to be used in the method described in paragraph [0016] for IN 939 in D4.

1.7 When adapting the method of D4, and being faced with D8, the skilled person would not necessarily increase also the cooling rate, despite the fact that D8 discloses that slow cooling rates lead to a decrease in the hardness of the alloy, as the respondent argued. D8, sentence bridging pages 2179 and 2180, discloses on the other hand that slow cooling rates provide an advantageous increase in ductility and thus it is up to the skilled person reading the document to choose which effect they would like to obtain.

As discussed above, the heating rate and the cooling rate provide different effects, so that when changing the heating rate, the skilled person does not need, necessarily, to also change the cooling rate, as this provides a different effect.

In addition, the method disclosed in paragraph 16 of D4, used as a starting point, and having a specific cooling rate already foresees that "other heating rates can be used in the practice of the invention". The skilled person is then aware that a change of the heating rate in the method in D4 can be carried out without changing the cooling rate as well.

Further, D4 (see for example in paragraphs [0004] and [0015] or claim 1) generally teaches that cooling rates below 3°F per minute and preferentially of 1°F per minute or less provide gamma prime precipitation in the gamma matrix improving weldability, so the skilled person looking for a suitable heating rate would not ignore the clear teaching of D4 and contemplate changing also the cooling rate.

Further, the reduction of hardness associated in D8 with slow cooling rates would not prompt the skilled person to change the cooling rate of D4, since this drawback is not related to the objective problem that the skilled person is trying to solve.

The same reasoning applies to the precipitation of M23C6 carbides as thin films at the grain boundaries, which is responsible for grain boundary embrittlement (as disclosed on page 2172, lines 18-20). This embrittlement results in a loss of ductility and could be responsible for (micro-)cracking at the grain boundary, but in operations after the heat treatment, which is not related to the objective problem that the skilled person is trying to solve.

1.8 For the above reasons, the subject-matter of claim 1 of the main request does not involve an inventive step (Article 56 EPC) when starting from D4 and, given the problem to be solved, considering the teaching of D8.

2. Auxiliary request - admittance

2.1 Claim 1 of the auxiliary request differs from claim 1 of the main request in that the nickel-based superalloy is defined as being "Waspaloy".

2.2 The request was filed during the oral proceedings, hence at the latest possible stage in the proceedings, and the Board needed to exercise its discretion as to whether the request should have been admitted into proceedings in accordance with Article 13(1) RPBA. In order to be admitted, inter alia the aspect of procedural economy given in Article 13(1) RPBA should be considered, which implies at least that the request should be prima facie allowable in the sense that it overcomes the objections raised without giving rise to new objections. This is however not the case for claim 1 of this request, for the following reasons.

2.3 As confirmed in D16, the Wikipedia article relating to WASPALOY filed by the respondent during the oral proceedings, WASPALOY is a registered trademark that refers to a nickel-based superalloy. The reliance on a trademark in claim 1 introduces a lack of clarity, since it cannot be guaranteed that the alloy referred to with the trademark WASPALOY has a single, established composition, nor that such composition stays constant over time.

2.4 The respondent argued that WASPALOY corresponded to a well defined known range of alloy compositions belonging to common general knowledge as demonstrated by D16 and disclosed a chemistry table with the minimum and maximum wt% values that each non-residual component of the alloy could have. The Board cannot accept this argument however, since, as shown e.g. in table 1 of D7, the chemical composition analysis of two WASPALOY samples in 2006 contained 0.05 and 0.07 wt% values of Niobium (Nb), respectively. The chemistry table of D16 does not even comprise Niobium, which is thus not part of the composition of WASPALOY in May 2018.

2.5 Contrary to the respondent's argument, the wt% values of Niobium cannot be considered as residual values such that the WASPALOY samples analysed in D7 also fall within the composition shown in D16. In this regard. the chemistry table of D16 discloses even smaller wt% values of other elements, such as Zirconium (Zr), Boron (B), Phosphorus (P) and Sulphur (S). If alloys carrying the designation WASPALOY in 2018 would still contain Nb, it would be expected that the latter element would necessarily appear in the elements listed in the chemistry table of D16. The trademark WASPALOY thus does not have such a well known meaning that would imply a constant and defined chemical composition belonging to common general knowledge of the skilled person. The introduction of the trademark WASPALOY in claim 1 thus renders the claim prima facie unclear.

2.6 As claim 1 of the auxiliary request prima facie does not meet the requirement of Article 84 EPC and is thus at least prima facie not allowable, the Board exercised its discretion not to admit this request into the proceedings (Article 13(1) RPBA).