Conventionally processed powder metallurgy materials often exhibit open microporosity at the surface. While it is a natural part of the process, this microporosity can affect the measurement of surface finishes. To cover this and other issues that arise from measuring the surface finish of powder metallurgy, ASTM International Committee B09 on Metal Powders and Metal Powder Products has developed a new standard, B 946, Test Method for Surface Finish of Powder Metallurgy (P/M) Products. The new standard, which will be useful to end users and parts makers who are interested in the surface finish of a powder metallurgy component, is under the jurisdiction of Subcommittee B09.05 on Structural Parts.
Test Method B 946 covers measuring the surface finish of powder metallurgy products at all stages of manufacturing from green compact to fully hardened finished component. It also provides definitions and schematics for common surface finish parameters.
One of the issues discussed in B 946 is the type of stylus used to measure surface finish. “Depending upon the size of the porosity and measurement stylus, a typical conical stylus may drop into the surface porosity and result in an artificially high surface roughness in comparison to a wrought material,” says Denis Christopherson, research and development manager, Federal-Mogul Sintered Products. “By using a chisel point stylus, the surface porosity of the work piece is discounted, providing more of a level playing field between powder metallurgy and wrought surface finish values.”
Subcommittee B09.05 encourages participation in future editions of the standard. “Experts in the area of surface finish are welcome to comment and offer suggestions for improvement,” says Christopherson. “The rapid advances in technology requires diligence from Committee B09 to keep the standard up-to-date.”
For further technical information, contact Denis Christopherson, Federal-Mogul Sintered Products, Waupun, Wis. (phone: 920/324-7515; firstname.lastname@example.org). Committee B09 meets Oct. 25-27, during the October Committee Week in Atlanta, Ga. For membership or meeting information, contact Christine Sierk, ASTM International (phone: 610/832-9728; email@example.com).