Does The HAZ Have a Sharply Defined Boundary?
Does The HAZ Have a Sharply Defined Boundary?
(OP)
The attached photo is a closeup of a macroetch specimen where we applied a bed layer (two passes) in a .125" deep groove then overlayed a .125" thick layer (two passes) of ECoCr-A surfacing. This is part of a welder qualification test. My question pertains to the darkest grey band below the bed layer. I would guess that this is a demonstration of how deep the HAZ will extend by the weld procedure used.
If I am right and this band is a portrayal of the HAZ, I would like to know why the HAZ has such a sharply defined boundary? I was always of the idea that HAZ was a gradually diminishing area that was related to the varying temperature differential. And why is this band darker than the unaffected base metal?
Please explain for the curious and thankyou very much.
If I am right and this band is a portrayal of the HAZ, I would like to know why the HAZ has such a sharply defined boundary? I was always of the idea that HAZ was a gradually diminishing area that was related to the varying temperature differential. And why is this band darker than the unaffected base metal?
Please explain for the curious and thankyou very much.





RE: Does The HAZ Have a Sharply Defined Boundary?
RE: Does The HAZ Have a Sharply Defined Boundary?
RE: Does The HAZ Have a Sharply Defined Boundary?
This is a typical HAZ appearance after macroetching. The sharpness or boundary of the HAZ from macroetching is a function of the welding process used, preheat, base metal composition and etchant, as mentioned by GRoberts.
RE: Does The HAZ Have a Sharply Defined Boundary?
RE: Does The HAZ Have a Sharply Defined Boundary?
C .07 - .13
Mg .40 - .70
Si .15 - .35
Cr 1.00-1.40
Ni 3.00-3.50
Mo .15 max
B 10ppm
Cu .35 max
How would you expect the 9310 HAZ to behave? Will it develop a hardened zone? that can be annealed by a PWHT at 1100 deg F for an hour? The reason I ask, is that the carbon content seems so low, like mild steel, that maybe this material won’t develop a hardened zone.
What role does the high nickel and chromium play in developing hardened weld affected areas?
Thanks for helping.
RE: Does The HAZ Have a Sharply Defined Boundary?
The hardness of the HAZ will be affected by carbon content; the lower the carbon, the lower the hardness. The depth or width of the HAZ will be affected by alloy elements that increase hardenability; like Ni and Cr.
To answer your question, the HAZ will have martensite and some bainite, as a result of the Ni and Cr alloy additions. Tempering the HAZ, not annealing, will result in tempered martensite and bainite with reduced residual stress - all good things to improve toughness.
RE: Does The HAZ Have a Sharply Defined Boundary?
RE: Does The HAZ Have a Sharply Defined Boundary?
The hardness of martensite and bainite formed in a HAZ or in air hardenable steels (it really does not matter) is directly proportional to carbon content. You can obtain this information from either ASME Handbooks or any metallurgical engineering text book
RE: Does The HAZ Have a Sharply Defined Boundary?