PVD vs CVD: How to Choose the Right Tool Coating

you I'm Pete szalinski with modern machine shop magazine and I am here with dr. Julia Shoop machining expert at tech solve and we're going to talk about coatings coatings the the thing that gives your cutting tool this elegant color Julius why do we coat tools what is the coating doing and machinings I like to think that there's three main effects that these coatings have I think there's where is this since that's offered because the coating is harder there's a thermal barrier and then there's lubricity which can help act kind of like a lubricant if you're cutting dry okay so these terms I mentioned PVD CVD what do they mean well PVD stands for physical vapor deposition and PVD coatings can be applied in a line-of-sight process that allows you to coat very sharp edges now cv d stands for chemical vapor deposition and this chemical vapor requires much higher temperatures and even though you're not limited to line-of-sight you need to apply the coating much thicker so let's just skip ahead to the main take away how should we think about PVD versus CVD and where these different type of types of coatings apply yeah absolutely the PVD coatings because they are thinner they are generally applied to more finishing type tools because you can get a sharper cutting edge the CVD coatings are thicker and they provide a better thermal barrier so they're actually better for roughing a lot of times we actually have machining footage to illustrate this here are roughing passes here is an uncoated tool here is a PVD coated tool and here is a CVD coated tool Julius in these roughing passes what have we seen well I think what we saw right away was that the uncoated tool that's significantly worse than either of the PVD or CVD tools and this goes back to the fact that the coating on both the PVD and CVD provided a level of protection and the level of lubrication that really helped them perform very well in this dry process the uncoated tool didn't have any of that protection and so it failed prematurely even before completing a single pass between PVD and CVD I think the differences are maybe slightly more subtle but we could definitely see a lot more vibrate with a PVD tool in this cut and that goes back to the sharper cutting edge this sharper edge and the more positive geometry of the PVD tool led it to perform much more like a like a chisel being pushed over some hard material rather than a rake being pulled over sand so let's look at those cutting edges here is the uncoated tool here is the PVD coated tool here's the CVD coated tool I think the uncoated tool had catastrophic failure which is because the lack of lubrication and thermal barrier on the rake face caused the chip to dig into the tool which is what we call crater where and this actually may weaken the edge to the point that it actually broke out if we look at the PVD tool we see a similar pattern but it's much less pronounced and then in the CVD we can see very little of crater wear which actually led to the much more stable wear pattern of the CVD tool that was roughing let's take a look at finishing same tools same passes except their finishing cuts now here is the uncoated tool here's the PVD coated tool here's the CVD coated tool yeah I think it was interesting how the same patterns that we saw in roughing showed up again in finishing but maybe in a slightly different way and from a different angle so the uncoated tool it started out pretty well but it just couldn't last through even a single cut which tells me that for dry machining we really want to have a coating now between PVD and CVD remember that I said that the PVD coating is actually slightly sharper well I think we saw that this sharpness is actually a big advantage in finishing not only are we generating lower cutting forces but at the same time we're also able to break the chip because of the more positive geometry here the cutting edges here's the uncoated tool here is the PVD coated tool here's the CBD coated tool I would say that the uncoated tool clearly has much much more wear than the other two tools had and this is because the absence of a coating the lack of lubrication in dry machining caused the workpiece material to erode the tool much more rapidly combination of increased heat and less lubrication the sharper PVD tool definitely did much better in the actual process because it was able to break the chip so I think the edge in this case no pun intended goes to the PVD tool so tie a bow around all this how should we think about PVD and CVD where they fit in opt I would say in summary think of CVD for roughing and PVD for finishing

Channel: Modern Machine Shop

Views: 89,082

Keywords: cutting tools, cutting tool coatings, Peter Zelinski, Pete Zelinski, Modern Machine Shop, Modern Machine Shop magazine, Julius Schoop, TechSolve, manufacturing consulting firm, manufacturing, manfuacturing consulting, machining, physical vapor deposition, PVD, chemical vapor deposition, CVD, CVD coating, PVD coating, coating process, difference between PVD and CVD coatings

Id: CH3IsHP7llM

Length: 5min 1sec (301 seconds)

Published: Thu Oct 04 2018