DE102007011728A1 - Method for determining hardness difference of layer applied by coating process before and after process change, involves determining hardness difference, which is determined by determination of density before and after process change - Google Patents

Abstract

The method involves determining the hardness difference is determined by determination of the density before and after a process change by using before the process change. The coating process is a thermal plasma spraying method. A powder agglomerate bonding agent hexagonal boron nitride core is enclosed by cobalt-nickel-chromium-aluminum-yttrium coating and polyester is used as coating material. An independent claim is also included for a device for manufacturing a defined geometry in form of a mold.

Description

The The invention relates to a method of time and material saving checking the coating quality in particular plasma-sprayed layers.

In According to DIN 8580, plasma spraying will become part of the group of prototype as well as the coating process counted. It includes according to EN 657, all processes in which spray additives within or outside of pointed devices, melted or melted down become. These spray additives are usually spiked or sprayed powder, when treating on workpiece surfaces knock down. The surfaces themselves are not melted. For this reason, a variety of different Coat materials.

The plasma coatings thus produced are used in a variety of fields. These range from purely decorative applications to highly stressed components; For example, plasma coatings are also used in the field of gas turbines. Here they serve, for example, to increase the mechanical and / or thermal resistance of particularly stressed parts such. B. turbine blades and housings. Another application in this area is the creation of extremely narrow gaps, which are indispensable for increasing the efficiency. For this purpose, the layers are applied so that they initially have a slight oversize, which then abrades during operation, so that the moving and the stationary parts have only minimal play. Preferably, agglomerates of a plurality of components are used here as spray powder, particularly preferably those which are composed of a matrix-forming component, a dry lubricant and a plastic. Such a spray powder is z. B. from the EP 0487 273 B1 known.

Around the quality of treatment such as the property the hardness of the coating are known, the prior art applied method. Especially in the determination of coating hardnesses on highly stressed It is necessary to share these before the final parameter determination Heat treatment steps suspend, if this on Follow the coating, as the layer hardness during changed this subsequent treatment steps.

The large number of possible, on the final result influence taking parameters makes quality control both difficult the manufacturing process itself, as well as the control of its result, the coating.

vorgenommen. Eine geringere Eindringtiefe entspricht demnach einem härteren Material, woraus sich ein größerer Wert für HRC ergibt.For the quality control of the coating result, the known methods such as hardness measurement and layer thickness determination are used according to the prior art. In particular, the test of hardness according to Rockwell HRC should be mentioned here. To measure them, the difference of the penetration depth t _{b of} a diamond cone is determined for hard materials, which results between the abandonment of a pre-load and a main load. The C stands for English. "Cone" Then a conversion according to the formula

performed. A lower penetration corresponds to a harder material, resulting in a higher value for HRC.

In particular for thin sheets, coatings and the like, the slightly modified measuring method according to HR15Y is used. Instead of the cone one uses here a ball with the diameter 12.7 mm as well as for the load a mass of 15 kg. The hardness is then determined according to the formula

at the result control of the coating process and here in particular the coating hardness measurement then disadvantages when the coated component after the coating process yet subjected to further, in particular heat treatment steps must become. Because such heat treatments in general at least a few hours, in some cases a few Days can last only at the end of this period a statement about the quality of the coating process or the coating result. Should not this be the specific one Meet requirements is one or more repetitions of the whole process including the heat treatment necessary to get to the desired results. In addition to the considerable loss of time, this also results in high levels financial losses, as appropriate for each iteration Dummy parts must be kept, treated and checked.

Also process changes that z. B. caused by a powder change or a burner maintenance, can lead to quality changes and, accordingly, the need for their review, which in turn result in the disadvantages mentioned. In addition, there is also often production downtime until a release of the geä changed process can take place.

Therefore the object of the present invention is to provide a method and a device for determining process change-related changes of material characteristics and in particular of hardness parameters after, for example, a plasma spray treatment, bypassing the disadvantages mentioned in the prior art, including in particular the need to stock dummy parts and the need the performance of possibly to the plasma spray treatment subsequent treatment steps counts.

These The object is achieved by a method with the features of claim 1 and by a device with the features of claim 10 solved. Advantageous developments of Invention are specified in the subclaims.

The invention describes a method for determining the hardness difference HR ₂ -HR ₁ from a layer applied by a coating method before and after a process change, characterized in that the determination of the hardness difference on a determination of the density ρ ₁ before and ρ ₂ after the process change under Using the known hardness HR ₁ before the process change by means of the formula MR 2 - MR 1 = (ρ 2 - ρ 1 ) × Z where Z is a constant dependent on the material of the deposited layer.

Of the Index "1" stands for values that precede the process change the index "2" stands for Values that are recorded after the process change. The constant Z is thereby once in advance for each applied material determined by hardness measurements and but remains about various process changes equal.

The The method is therefore based on the knowledge that the density difference two layers, which are treated with a substantially similar process, but were made with some variation of the process parameters, proportional to the hardness difference of these layers, taking into account a proportionality factor to be determined is.

• (a) Bereitstellung einer Probe Zur Durchführung des Verfahrens werden bevorzugt so genannte Knopfproben verwendet. Diese bestehen aus dem Zielmaterial, besitzen jedoch nicht die Zielform, sondern haben besonders bevorzugt eine einfache geometrische Form, die zu günstigen Kosten herstellbar ist.
• (b) Bestimmung des Gewichtes und der Maße der Probe Mittels geeigneter Messverfahren werden das Gewicht und die genauen Maße der Probe bestimmt. Diese Daten dienen der späteren Bestimmung des Volumens und der Masse der Beschichtung.
• (c) Beschichten der Probe durch einen Beschichtungsprozess Das Beschichten der Knopfprobe erfolgt mit dem gewählten Beschichtungsverfahren. Dies geschieht erfindungsgemäß bei einer ersten Probe bevor eine Änderung der Prozessparameter erfolgt, und bei einer zweiten Probe, nachdem eine Änderung der Prozessparameter erfolgt ist.
• (d) Herstellen einer definierten Geometrie auf der Probe Mittels einer geeigneten Vorrichtung und besonders bevorzugt mit Hilfe der erfindungsgemäßen Vorrichtung wird eine definierte Geometrie auf der Probe erzeugt. Als Verfahren zur Herstellung der definierte Geometrie kommen vor bevorzugt spanabhebende Verfahren, und besonders bevorzugt das Drehen in Frage.
• (e) erneute Bestimmung des Gewichtes und der Maße der Probe.
• Im Anschluss an einen bevorzugterweise vorangehenden Reinigungsschritt, bei welchem beispielsweise Spritzer an der Mantelfläche der Probe entfernt werden, werden anschließend wiederum das genaue Gewicht und die Maße der nun beschichteten Probe bestimmt.

An advantageous development of the method according to the invention provides the following steps:

• (a) Provision of a Sample For carrying out the method, so-called button samples are preferably used. These consist of the target material, but do not have the target shape, but more preferably have a simple geometric shape that can be produced at low cost.
• (b) Determination of the weight and dimensions of the sample By means of suitable measuring methods, the weight and the exact dimensions of the sample are determined. These data are used to determine the volume and mass of the coating later.
• (c) coating the sample by a coating process The coating of the button sample is carried out with the chosen coating method. This is done according to the invention in a first sample before a change in the process parameters, and in a second sample after a change in the process parameters has occurred.
• (d) Producing a Defined Geometry on the Sample By means of a suitable device and particularly preferably with the aid of the device according to the invention, a defined geometry is generated on the sample. As a method for the production of the defined geometry come before preferably cutting processes, and particularly preferably turning into question.
• (e) re-determining the weight and dimensions of the sample.
• Subsequent to a preferably preceding cleaning step, in which, for example, splashes are removed on the lateral surface of the sample, the exact weight and the dimensions of the now coated sample are then determined again.

As already mentioned in (c), steps (a) to (e) become first with the original process with a first sample and then with the modified Process performed with a second sample. such Process changes can be made, for example, by Maintenance work on the coating process Plant, by batch or powder change, or by trial and error Process parameter changes are brought about. In accordance with the invention, this can be accomplished the process change at any time after the coating of the first sample, but at the latest directly before coating the second sample.

At the The end of both coating experiments are according to the invention two Samples as well as their geometries and weights, both before and also recorded after the implementation of the respective coating were.

• (f) Bestimmung der mittleren Dichte der Beschichtungen beider Proben Anhand des einfachen, bekannten Zusammenhangs von Volumen, Masse und Dichte eines Körpers
  
  kann die Dichte der Beschichtung einer Probe bestimmt werden. Hierzu ist es notwendig, das Volumen und das Gewicht der Probe ohne die Beschichtung zu kennen, und dieses vom Gesamtvolumen und dem Gesamtgewicht der Probe nach der Beschichtung abzuziehen. Die hierzu notwendigen Werte wurden jeweils unter (b) und (e) erfasst. Es stehen dann zwei Dichtewerte ρ₁ und ρ₂ zur Verfügung, welche die Beschichtungsdichte vor bzw. nach der Prozessänderung angeben.
• (g) Bestimmung der zu erwartenden Härtedifferenz entsprechend Anspruch 1

The following steps now advantageously follow:

• (f) Determination of the mean density of the coating Both samples are based on the simple, known relationship of volume, mass and density of a body
  
  the density of the coating of a sample can be determined. For this purpose, it is necessary to know the volume and weight of the sample without the coating, and deduct this of the total volume and the total weight of the sample after the coating. The necessary values were recorded under (b) and (e). There are then two density values ρ ₁ and ρ ₂ available which indicate the coating density before or after the process change.
• (g) determination of the expected hardness difference according to claim 1

In a last step can now according to the invention Formula the hardness difference of the layers before and after the Process change can be estimated. Is this Difference zero, it can be assumed that the process change did not affect the hardness of the coating. Otherwise, depending on the sign of the density change closed on the sign of the hardness change become.

To a particularly preferred embodiment is also the hardness one of the coatings determined by means of appropriate measurement methods. By Switching the formula of the invention can then the missing hardness value is calculated.

by virtue of the knowledge of the layer hardness after performing the process change can now, if desired, an iterative adaptation of the process parameters carried out, for example the goal may be the layer hardness before the process change or to achieve a higher hardness.

The described method is particularly suitable for estimation of process-related hardness changes using of plasma spraying as a coating method.

In a particularly preferred embodiment of the invention that for carrying out the method according to the invention used samples a flat, cylindrical shape, for example by turning and with the aid of a suitable device can be generated and / or post-processed.

Especially it is also preferred to produce such layers which are thicker, as the layers on the parts to be coated later, since thus measuring errors, in particular during the thickness measurement, be minimized.

Especially the hardness measurement of the layer according to Rockwell is preferred and in particular according to HR15Y. This type of measurement becomes special preferred for thin layers of greater hardness applied.

Especially this applies to layers, which by plasma spraying of a powdered agglomerate of with binder and CoNiCrAlY surrounded hexagonal boronitide cores and polyester produced become. Such a powdery agglomerate is, for example available under the name SM2042 from Sulzer Metco. The for this material through two different coating processes and then hardness and density measurements certain constant Z is when specifying the hardness according to HR15Y 81.

to Production of the defined geometry is preferably a device used, which for turning the inventive Samples is suitable. This accordingly includes a cutting edge and a receptacle for the lathe chuck and is particularly preferably designed such that it has a predetermined Cutting angle, which of the simplified production of a blunt-conical geometry of the invention Sample and more preferably an additional one Facing the end face of the sample is used.

In a most preferred embodiment of the invention the angle provided by the device is 30 degrees.

By Use of the method according to the invention can very quickly a statement about the effects of a process change be taken because of the application of the method according to the invention No hardness measurement is necessary, which in turn is why would take a long time because of a hardness measurement only after completion of any time-consuming heat treatments possible as they often after coating be applied. Furthermore, no parts from the production in the form of dummy parts for carrying out the invention Method is required because even simple button samples are sufficient the only one short mechanical post-processing step be subjected. Thus, the invention achieves Method both a significant time savings as well as a cost reduction in quality control after process changes.

following is an advantageous method and an advantageous device described with reference to an embodiment. Show:

1 a schematic flow diagram for carrying out the method according to the invention;

2 a button sample according to the invention before and after processing by means of the device according to the invention;

3A -C particularly preferred variants of the device according to the invention.

1 shows a schematic flow diagram of the method according to the invention. This consists essentially of two very similar blocks, of which the coating in the first block is carried out with the original process (referred to as "process 1") and that in the second block with the modified process (referred to as "process 2"). As a result, the density of the respective process on the respective sample is in each case 1 applied layer 2 . 3 in the form of a numerical value.

Subsequently From the density values, the hardness difference becomes according to claim 1 of the method according to the invention.

To a variant of the method according to the invention may be at the end of a block, preferably that of the original one Process associated block is a hardness measurement of the applied Layer done. This makes it possible, in the connection to the calculation of the hardness difference also the determination to perform the respectively missing (not previously determined) hardness.

It Let's add that variations of those shown in the scheme Order are allowed insofar as long as the goal of the invention Method can be achieved. For example, the process change already directly after coating the first sample, or first after carrying out the measurements on this sample, however, at least immediately before coating the second Sample.

2 shows a section through a cylindrical sample 1 , a so-called button sample, as it is preferably used for the inventive method, together with a coating, which in the left half of the picture as unprocessed coating 2 , in the right half of the picture as a processed coating 3 is shown. While the former laterally over the lateral surface 5 the sample 1 protrudes and has an uneven surface, the latter is flat, closes flush with the lateral surface 5 the sample 1 and forms a predetermined angle at the transition 4 ,

In this context, it should be noted that the dimensions of the sample 1 and the layer 3 not to be considered to scale. In particular, however, those layers are preferred which have the greatest possible thickness, since the measurement error in their thickness determination can thus be reduced.

The lateral surface 5 the sample 1 should particularly preferably after completion of the coating, but before the measurement of unwanted foreign bodies such as spray residues are removed, but without damaging the surface. For this purpose, both manual methods such as sanding or scraping as well as automated methods such as turning apply.

The 3A -C show variants of a device according to the invention 6 for producing a defined sample geometry by means of turning, which is preferably necessary for the method according to the invention. All variants have in common the presence of at least one cutting edge 7 with an angle α, which engages with the sample during turning 1 is and their form to the test 1 transfers. Another common feature is the presence of a suitable clamping area 8th for receiving the device 1 into the chuck of the lathe.

The 3A shows a first variant of the device according to the invention 6 that attaching the angle 4 to the sample 1 serves.

3B shows an expanded embodiment of the device according to the invention 6 , which two cutting edges 7 one of which is for generating the angle α, the other for facing the top of the sample 1 is used, so that in one operation the angle 4 and the processed coating 3 result.

3C shows a more expanded embodiment of the device according to the invention 6 , which three cutting edges 7 of which the first for generating the angle α, the second for facing the top of the sample 1 , and the third to clean the lateral surface 5 is used, so that in one operation the angle 4 , the processed coating 3 , as well as a clean outer surface 5 result.

The variants presented here represent only a selection of further possibilities of the cutting edge design, the results of the same effect with respect to the possible simultaneous machining of more than one outer edge of the sample 1 achieve.

1

sample

2

unedited coating

3

edited coating

4

angle

5

lateral surface

6

contraption

7

cutting edge

8th

clamping

α

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0487273 B1 [0003]

Claims (11)

Method for determining the hardness difference HR ₂ -HR ₁ from a layer applied by a coating method before and after a process change, characterized in that the determination of the hardness difference via a determination of the density ρ ₁ before and ρ ₂ after the process change with the aid of the known hardness HR ₁ before the process change using the formula MR 2 - MR 1 = (ρ 2 - ρ 1 ) × Z is determined and Z is a dependent of the material of the applied layer constant. The method of claim 1, which comprises the following steps having: - Providing a sample; - Determine the weight and dimensions of the sample; - coating the sample through a coating process; - Produce a defined geometry on the sample; - again Determine the weight and dimensions of the sample for two samples, the first before and the second after a process change is coated; - Determine the mean density the coatings of both samples; - Determine the expected hardness difference according to claim 1. Method according to claim 1, which comprises the following steps: determining the hardness HR _{1 of} the coating of the sample before the process change of the coating process or the hardness HR _{2 of} the coating of the sample after process change of the coating process; Determining the respectively unknown hardness of the coating of the respective other sample HR ₂ or HR ₁ according to claim 1; - Adjustment of the manipulated variables of the coating process to compensate the determined according to claim 1 and 2 hardness difference. Method according to Claims 1 to 3, characterized the coating process is a thermal plasma spraying process is. Method according to Claims 1 to 3, characterized that the samples have a cylindrical shape. Method according to Claims 1 to 3, characterized that the production of the defined geometry by means of facing with the aid of a suitable device. Method according to claim 2, characterized in that that a minimization of the measurement error by an increase the layer thickness above that for the desired Component function necessary dimension beyond. Method according to Claims 1 to 7, characterized that the hardness to be determined according to Rockwell and in particular determined according to HR15Y. Method according to one of the preceding claims, characterized in that as a coating material is a powdery Agglomerate of hexagonal bound with binder and CoNiCrAlY Boronitide cores and polyester is used. Device for producing a defined geometry in the form of a template comprising a cutting edge and a receptacle for a lathe chuck, characterized in that the cutting edge is a conical rejuvenation of the lateral surface produced the rotating material and the end face of the rotating material plan rotates. Device according to claim 11, characterized in that that the angle made by the template is 30 °.