"Carbon Steel Castings
"Specification: ASTM A27 - Grade 65-35 or 70-40; and ASTM A216 -
"Application: These materials are commonly used for turbine runners and
wicket gates. Although steel castings have been used on other components
such as headcovers, discharge rings and stay rings, most of these turbine
parts are not of fabricated construction. ASTM A216 castings are of slightly
higher strength than the more commonly used ASTM A27 material. ASTM
A216 material is therefore used where increased mechanical strength is
"Stainless Steel Plate
"Specification: ASTM A167 - Type 304; ASTM A240 - Type 304
"Application: This material is used on all turbine components of stainless
steel plate construction. The material is an 18-8 austenitic stainless steel,
easily weldable and with strength equivalent to low strength carbon steel.
"Stainless Steel Castings (Martensitic)
"Specification: ASTM A487 - Grade CA-6NM; and ASTM A743 Grade CA-
"Application: CA-6NM castings are commonly used for turbine runners and
wicket gates. The material is a 13-4 martensitic stainless steel developed in
the early 1960's as an alternative to CA-15 stainless steel. The CA-6NM has
better casting behavior and improved weldability over CA-15 stainless steel.
Nevertheless, when welding CA-6NM, relatively high preheat and postweld
heat treatment is (sic) required to prevent cracking if martensitic weld material
is used. Field repairs with austenitic weld material are feasible with minimal
preheat and no postweld heat treatment; however, the deposited material
does not have the same strength as the CA-6NM base.
"This material is of relatively high strength, and has a cavitation resistance
comparable 304 stainless plate.
"Because of the relatively low chromium and nickel content, the material is
subject to pitting in salt water or a similarly corrosive environment. In some
installations, corrosion of CA-6NM material is believed to be a result