Problems in laser repair cladding a surface AISI D2 heat-treated tool steel

Abstract

The aim of the present work is to establish the relationship between laser cladding (LC) process parameters (power, process speed, and powder feed rate) and AISI D2 tool steel metallurgical transformations, with the objective of optimizing the processing conditions during real reparation. It has been deposited H13 tool steel powder on some steel substrates with different initial metallurgical status (annealed or tempered) using a coaxial LC system. The microstructure of the laser clad layer and substrate heat-affected zone (HAZ) was characterized by optical microscopy, scanning electron microscopy, and electron backscattered diffraction. Results show that the process parameters (power, process speed, feed rate, etc.) determine the dimensions of the clad layer and are related to the microstructure formation. Although it is simple to obtain geometrically acceptable clads (with the right shape and dimensions) in many cases some harmful effects occur, such as carbide dilution and non-equilibrium phase formation, which modify the mechanical properties of the coating. Specifically, the presence of retained austenite in the substrate–coating interface is directly related to the cooling rate and implies a hardness diminution that must be avoided. It has been verified that initial metallurgical state of the substrate has a big influence in the final result of the deposition. Tempered substrates imply higher laser absorption and heat accumulation than the ones in annealed condition. This produces a bigger HAZ. For this reason, it is necessary to optimize the process conditions for each repair in order to improve the working behaviour of the component.

Keywords:

• laser cladding
• tool steel
• EBSD
• austenite
• microstructure

Acknowledgements

The authors thank the Ministry of Education and Science for the financing of this investigation through project DPI2005-09244-C04-04 under the Industrial Production Programme of the National Plan and its continuity with project MAT2008-06882-C04-04/MAT of the Ministry of Science and Innovation.

Notes

^1. [email protected]

^2. [email protected]

^3. [email protected]

^4. [email protected]

Additional information

Notes on contributors

J. J. Candel

1 1. [email protected]

V. Amigó

2 2. [email protected]

J. A. Ramos

3 3. [email protected]

D. Busquets

4 4. [email protected]