Final Separation Agreement

Exhibit 10.1

July 29, 2008

Mr. Chris Ayers

16311 Kyle Crest Trail

Cypress, Texas 77433

Dear Chris:

As we have discussed, you have informed us that you wish to resign your employment with Wyman-Gordon. In order to facilitate an amicable separation and to assist you in this period of transition, Wyman-Gordon is offering you the severance arrangement set forth in this Separation Agreement (the “Agreement”).

Effective July 25, 2008, you resigned as an officer of Precision Castparts Corp. (“PCC”) and as a director and officer of the subsidiaries for which you serve as a director or officer. Upon execution of this Agreement, PCC will cause Wyman-Gordon Forgings, Inc. (“Wyman-Gordon”) to continue your employment from July 25, 2008 through December 31, 2008 (the “Termination Date”), subject to earlier termination pursuant to paragraph 7, below (the “Continuation Period”). You will have no formal duties or authorities during the Continuation Period to PCC and any of its subsidiaries or affiliates (hereafter collectively referred to as the “Company”) except to make yourself available upon request of your successor or Mark Donegan to provide information or assistance as they reasonably determine, and to fulfill such reasonable requests in a professional and workmanlike manner and in compliance with Company policies.

You have agreed to resign your positions as an officer of PCC and as an officer and director of the Company, such resignations to be effective July 25, 2008.

(A) You will receive your current salary and benefits (defined as health, life and disability insurance coverage, 401(k) participation, your current company-leased vehicle and Employee Stock Purchase Plan participation; hereafter the “Benefits”) during the Continuation Period, except that you agree (i) you will not be eligible to receive a bonus in respect of fiscal 2009, (ii) you will not be eligible for additional option grants in fiscal 2009, (iii) during the

Mr. Chris Ayers

July 29, 2008

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Final Separation Agreement

Continuation Period you will use any accrued vacation time you have as of the date of this Agreement; (iv) you will not accrue any vacation or sick leave during the Continuation Period; and (v) you agree that the change of control agreement between you and the Company dated May 2, 2005 is terminated in full as of July 25, 2008.

(B) Your existing group health insurance coverage continues through the end of the last month of your employment. After that time, you may be eligible for continuation coverage under a federal law that is referred to as “COBRA.” Further information concerning COBRA coverage options and rates will be provided to you in separate correspondence. COBRA coverage may be available to you at your own expense regardless of whether you enter into this Agreement.

(C) As a terminating employee, you should be aware that your Company-provided basic life insurance coverage will end on the last day of the month in which your employment terminates. You may have certain rights to convert to an individual life policy. Further information regarding conversion of your life insurance benefits to an individual policy is provided by the Company’s life insurance carrier. In addition, your long-term disability insurance coverage ends when your employment terminates. You will retain any vested rights you may have under the Company 401(k) Plan. Your rights and benefits are governed by the terms of that Plan. You can contact Fidelity direct at 1-800-835-5095 to request a distribution, if you wish. Alternately, you may leave your account balance in place with our plan under Fidelity.

(D) The amounts in your account under the PCC Executive Deferred Compensation Plan will be paid to you pursuant to the provisions of such plan. Please refer to the plan at http://www.sec.gov/Archives/edgar/data/79958/000119312508124576/dex1015.htm for more details. You have vested accrued retirement benefits under the Wyman-Gordon Company Retirement Income Plan (the “Wyman-Gordon Retirement Plan”) and under the Precision Castparts Corp. Retirement Plan (the “PCC Retirement Plan”). Your rights and benefits are governed by the terms of each plan. Under those plans, written statements describing vested accrued benefits are routinely sent after employment termination, participants’ benefit payments ordinarily start at normal or early retirement age and pre-retirement death benefits may be payable. Your age and service combined are not sufficient to qualify for any vested accrued benefit under the Precision Castparts Corp. Supplemental Executive Retirement Program – Level One Plan Ongoing (“SERP”). Upon employment termination, your SERP participation will end with no benefit payable. If you have any questions about these plans, you can contact Tammy Aber (Wyman-Gordon Retirement Plan) at 281-856-3207, Beth Wachtman (PCC Retirement Plan) at 503-772-6628 or Steve Blackmore (SERP) at 503-417-4808.

(E) We agree that during the Continuation Period you will not be subject to PCC’s Stock Ownership Guidelines or its Pre-Clearance and Blackout Period Procedures. Please be aware that these are internal guidelines and have no impact on laws governing insider trading which you will be subject to so long as you have material nonpublic information about the

Mr. Chris Ayers

July 29, 2008

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Final Separation Agreement

Company. Also note that you are currently subject to Section 16(b) of the Securities Exchange Act of 1934 which has provisions on “short swing” profits. Depending on your trading activity, Section 16(b) may or may not be an issue for you. You should consult your advisors on the matter.

You acknowledge and re-affirm as a term of this Agreement, your continuing obligations to the Company pursuant to the Employee Agreement which you entered into on January 30, 2003 and the Non-Disclosure and Inventions Agreement which you entered into on July 13, 1999. A copy of those Agreements is enclosed and they are incorporated by reference into this Agreement. You further acknowledge that you have a duty as a former officer and employee of the Company to keep confidential all proprietary or confidential information obtained by you during the course of your employment with the Company. During the course of your employment, you have had access to and have used substantial amounts of Company confidential and proprietary information, including, but not limited to, manufacturing processes and procedures, customer information, strategic planning information, acquisition planning and strategy information, human resources information, company policies, procedures and objectives, Company financial information and other Company operating information. This information is considered also to be trade secrets of the Company. Accordingly, you agree to maintain the confidentiality of all such information when you leave the Company’s employment. You understand that your disclosure of this information to anyone may subject you and any other user of that information to legal and equitable claims by the Company. You agree to maintain all such information on a confidential basis and not to disclose it to any person except when required by law, e.g., upon subpoena by a government agency. You agree to promptly notify the Company or its attorneys whenever you receive a summons, subpoena, or other request for such information and to allow the Company reasonable time to contest the disclosure of such information before any required disclosure is made.

You have requested and the Company has agreed to formulate the separation arrangement set forth in this Agreement on terms that will permit you to remain as an employee of Wyman-Gordon through the November 2008 vesting dates under the 2001 Stock Incentive Plan to which you are a party. All outstanding options will continue to be governed by the terms of your stock option award agreements and the 2001 Stock Incentive Plan. Please refer to the plan at http://www.sec.gov/Archives/edgar/data/79958/000104746904020259/a2138155zex-10_14.htm for additional information. We estimate that the value of the option and salary and benefit continuation provisions of this Agreement (the “Consideration”) will amount to