Forging super alloy and super stainless is not an easy job. Working these alloys usually requires twice as much power as other alloy or stainless products. This is due to the alloys being very strong through their chemical composition - higher alloy grades inherently have greater value. That inherent value is before you even cut it, heat it and form it to the shapes and sizes required. Having the right size billet starting stock makes a difference in the overall forging time required and the resultant mechanical properties the item will have. The chances a forging house will be able to make a small part successfully is dependent upon the input billet, how many pieces regularly required and over how many years it will run.
When requesting a quotation for a forging, it is very helpful to provide the finished dimensions, and allow sales to provide the oversize amount needed to guarantee the part can be machined. It may be more stock to remove than you would like, but you should only have to machine it once. Some materials are tougher to forge and machine than others. If you have never machined the item before, this is a good time to talk to sales about machinability and tooling needs. Many times machine shops will win an order due to machine time underestimate. Some of these alloys will take twice as long to machine, due to the removal rates are not as good with the higher tensile and yield strengths.
Forgings can be provided in a multitude of ways and they have different amounts of value added service. Forging option for open die forgings are as follows: oversized with allowance to finish, rough ground, rough machined, and finish machined per print. We also can perform inspections at this stage (above and beyond the AMS/ASTM material requirements). Whether it is an ultrasonic to various criteria, charpy V notch, magnetic permeability, dye penetrant or radiograph - it is always best to use these types of inspections early when they can be performed early and with less complex geometry.
Most of our customers require actual mechanical testing for their forgings. The controlling specification would have an indication of whether testing is required, but the application or usage of that part is what should dictate the need. A non critical part could be verified that is has been supplied correctly through a simple hardness check. The options for actual mechanicals are testing from a forged coupon, using a prolongation of the piece or cut from item, and actually destroying a piece to determine properties. Separately forged test coupons are normally the route taken, and provide a great insight to the properties of the actual forging. The actual forging should be hardness tested and compared to the coupon hardness to correlate the two properties. Using a prolongation or destroying the sample will provide results that can certify a batch as well, these would be used for more critical type requirements and help show how the material is responding in "as used" cross sections.
