Process for producing crack-free nitride-hardened surface on titanium by laser beams
AssigneeIngersoll-Rand Company
InventorsWilliam J. Gavigan, Craig L. Snyder, Frank J. Tufano, Ronald S. Miller
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Abstract
A process for producing a crack-free, laser nitride-hardened layer on a titanium substrate, the process including preheating the substrate, melting a small area of substrate with a laser, and shrouding the melted area with a gas mixture having a maximum critical amount of nitrogen not greater than 85%. A crack-free pump shaft so hardened to Rockwell 52 C is produced.
Claims14
A process for nitride-hardening a surface of a titanium alloy substrate, without cracking of the substrate, comprising:
- (a) providing a commercially pure substrate of titanium;
- (b) preheating said substrate to a range of between 1000 F. and 1200 degrees F.;
- (c) applying a high-density energy source to the surface of said substrate to cause localized areas of melted substrate surface;
- (d) scanning said energy source along the surface of said substrate to cause said localized melting to move over an area to be hardened;
- (e) simultaneously shrouding said melted substrate surface in a gaseous atmosphere containing, by volume, at least 70% but not more than 85% nitrogen, and the balance one or more gases that do not react with molten titanium, to cause absorption of nitrogen into said melted substrate;
- (f) solidifying said melted substrate to form a hardened surface layer on said substrate comprising a matrix of titanium, with TiN particles dispersed therein said surface layer characterized by a minimum hardness of 50 Rockwell C and being free from cracking;
- and
- (g) slow cooling said substrate.
A process for producing on a titanium alloy substrate a nitride hardened surface highly resistant to cracking comprising:
- (a) providing a titanium substrate;
- (b) preheating said substrate to a range of between 1000 and 1200 degrees F.;
- (c) applying a high-density energy source to the surface of said substrate to cause localized areas of melted substrate surface;
- (d) scanning said energy source along the surface of said substrate to cause said localized melting to move over an area to be hardened;
- (e) simultaneously shrouding said melted substrate surface in a gaseous atmosphere containing, by volume, not more than 85% nitrogen, and the balance one or more gases that do not react with molten titanium, to cause absorption of nitrogen into said melted substrate;
- (f) solidifying said melted substrate to form a hardened surface layer on said substrate comprising a matrix of titanium, with TiN particles dispersed therein said surface layer characterized by a minimum hardness of 50 Rockwell C and being free from cracking;
- and
- (g) slow cooling said substrate at a cooling rate in the range of between 30 and 60 degrees F./hour.
A process for nitride-hardening a surface of a titanium alloy substrate, without cracking of the substrate, comprising:
- (a) providing a commercially pure substrate of titanium;
- (b) preheating said substrate to a range of between 1000 F. and 1200 degrees F.;
- (c) applying a high-density energy source to the surface of said substrate to cause localized areas of melted substrate surface;
- (d) scanning said energy source along the surface of said substrate to cause said localized melting to move over an area to be hardened;
- (e) simultaneously shrouding said melted substrate surface in a gaseous atmosphere containing, by volume, at least 70% but not more than 85% nitrogen, and the balance one or more gases selected from the group consisting essentially of argon and helium, to cause absorption of nitrogen into said melted substrate;
- (f) solidifying said melted substrate to form a hardened surface layer on said substrate comprising a matrix of titanium, with TiN particles dispersed therein said surface layer characterized by a minimum hardness of 50 Rockwell C and being free from cracking;
- and
- (g) slow cooling said substrate at a cooling rate in the range of between 30 and 60 degrees F./hour.
Dependencies are inferred from the claim text.