Here’s one for the machinists on here! The wealth of knowledge may have some experience...
without going into masses of depth, a component requires weld build up due to excessive wear. It is then required to be machined back to a pre-determined profile as per oem specs. It is to be machined in situ, with portable equipment.
basically the composition of the weld material consists of (without considering base material dilution) 54% cobalt, 26% chromium, then a bit of molybdenum, iron, a sprinkle of tungsten and some other elements making up the remaining fraction of a percent.
Given its overwhelming proportions of cobalt and chromium it is safe to assume it’s relatively tough. I was trying to think of a good analogy earlier but imagine trying to dig through concrete with butter. Superalloys like to work close to their melting point so shearing them when machining can put a lot of heat into the tool. They also like to work harden for fun which makes the following pass even more difficult. This composition is also extremely resilient to wear and corrosion which is why it is selected for its application. But of course it means machining is difficult.
our current situation is such that we have a semi rigid setup with hydraulic drive which isn’t as powerful as it really needs to be but under normal circumstances would be plenty powerful. The rigidity is the main problem but with in-situ you are limited to what you have.
tooling for the job clearly is carbide. HHS cuts beautifully for about 10 seconds then it rubs it away like it’s made of chocolate. I have experimented with various blends of brazed tipped carbide tooling with some positive results, certain grades are definitely better than others. I have also experimented with changes of speeds and differing rake angles and clearance and found a positive rake angle is essential to reduce the effort required to shear the weld material. If not, tool chatter becomes your biggest concern. Of course a certain amount of clearance is required but excessive can result in premature tool failure of the catastrophic kind. A few have been literally smashed with surprising little effort.
id be very surprised if anyone has had a similar experience but some may have exposure to this material and cutting it. I have got a method of producing satisfactory results and once your under the skin it’s not too horrible to machine but of course you have to get there first! I’m going to have a play with this over the winter, if it were single point machining it wouldn’t be an issue, cbn would likely do the trick but when you need to cut an arc with a machine that only feeds in two axis it gets difficult...
And suggestions or advice welcomed!
without going into masses of depth, a component requires weld build up due to excessive wear. It is then required to be machined back to a pre-determined profile as per oem specs. It is to be machined in situ, with portable equipment.
basically the composition of the weld material consists of (without considering base material dilution) 54% cobalt, 26% chromium, then a bit of molybdenum, iron, a sprinkle of tungsten and some other elements making up the remaining fraction of a percent.
Given its overwhelming proportions of cobalt and chromium it is safe to assume it’s relatively tough. I was trying to think of a good analogy earlier but imagine trying to dig through concrete with butter. Superalloys like to work close to their melting point so shearing them when machining can put a lot of heat into the tool. They also like to work harden for fun which makes the following pass even more difficult. This composition is also extremely resilient to wear and corrosion which is why it is selected for its application. But of course it means machining is difficult.
our current situation is such that we have a semi rigid setup with hydraulic drive which isn’t as powerful as it really needs to be but under normal circumstances would be plenty powerful. The rigidity is the main problem but with in-situ you are limited to what you have.
tooling for the job clearly is carbide. HHS cuts beautifully for about 10 seconds then it rubs it away like it’s made of chocolate. I have experimented with various blends of brazed tipped carbide tooling with some positive results, certain grades are definitely better than others. I have also experimented with changes of speeds and differing rake angles and clearance and found a positive rake angle is essential to reduce the effort required to shear the weld material. If not, tool chatter becomes your biggest concern. Of course a certain amount of clearance is required but excessive can result in premature tool failure of the catastrophic kind. A few have been literally smashed with surprising little effort.
id be very surprised if anyone has had a similar experience but some may have exposure to this material and cutting it. I have got a method of producing satisfactory results and once your under the skin it’s not too horrible to machine but of course you have to get there first! I’m going to have a play with this over the winter, if it were single point machining it wouldn’t be an issue, cbn would likely do the trick but when you need to cut an arc with a machine that only feeds in two axis it gets difficult...
And suggestions or advice welcomed!