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Cracked Saw Tips on a Finished Saw Blade

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Cracked Saw Tips on a Finished Saw Blade

A customer wrote to us for an analysis on cracked saw tips on a finished saw blade.  We gave our analysis based on what we saw from the saw tips they sent us.  For more information on when and why carbide Saw tips crack read our article on Crack Propogation in Carbide, or refer to our Carbide and Advanced material Index.

(Email from client)

“May we wonder you esteemed company offer analysis for saw tips? Now we have got a problem. One of our clients informed us that our tips cracked after brazing onto the saw blade. But the tips have no quality problem before welding. So is it possible that you kindly help us to figure where the problem lies in. We thank you for your kind support in advance.  

Enclosed please kindly find an analysis report for the tips before brazing, we hope that might be of help to your analysis. And below also the brazing skill offered by our client," 

Brazing temp. 740 Celsius (1364F)

Brazing time:  10 seconds.

Automatic brazing. 

Grade of carbide:

3.2% Co

15.03 g/cc

Hardness 94.5 

By means of a metallurgical hardmetal analysis it should be determined if the crack has already been in the raw, unsoldered parts or if they are caused by soldering or grinding.

On the saw blade with flat teeth we have seen eight defect teeth.  On all those teeth you can see cracks (picture 1 - 8) but the cracks are only on one side of the hardmetal tooth.  

 cracked_tips_on_saw_blades-1.jpg

 cracked_tips_on_saw_blades-2.jpg

cracked_tips_on_saw_blades-3.jpg 

cracked_tips_on_saw_blades-4.jpg 

The back side doesn’t show any cracks on the determined teeth (picture 9). As the crack propagation is not parallel to the brazing surface the evidence of a brazing stress related failure of the teeth seems to be very low. 

Due to the macro structure of the crack it seems more obviously that a pressing problem has created this kind of defects. The saw plate with the negative crown shows a scratch on the tooth surface.

 cracked_tips_on_saw_blades-5.jpg

My Comment:  Because the cracks are extremely similar in size and shape, it appears this is a pressing problem. 

Here is what cracks look like when it is a grinding problem.  In this case the wheel was dull or clogged, maybe too much force was used.  In any case the tooth got way too hot and cracked.  

cracked_tips_on_saw_blades-6.jpg 

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