WO2018197184A1 - Modifying the power during wobbling - Google Patents

Abstract

During the wobbling process, the laser power (P) is lowered for a short period of time in the region of the cusps (16', 16",...), thus allowing for better welding results.

Description

 Change in power at the wobble

The invention relates to an adaptation of the power during the wobble of an order strategy during welding.

Welding processes are carried out on metallic components in order to apply missing material or to achieve three-dimensional structures. Laser welding processes, in particular powder application processes, in particular laser powder deposition welding processes, are currently frequently used. In these methods, but also in other methods in which powder or the material is supplied in any other way, a Wobbeistrategie is applied, in which the energy beam and substrate oscillate relative to each other.

This can be done by causing the laser beam and / or material beam to oscillate relative to the substrate or by oscillating the substrate through a vibrating system or both. Further possibilities for generating the wobble strategy are also possible.

By a Wöbbel strategy when laser cladding a nucleation and grain growth in the mushy zone can be produced selectively so that the growth of a co- lumnaren solidification front is suppressed or completely avoided ^¬ ver. It is therefore an object of the invention to further improve the above-mentioned method.

The object is achieved by a method according to claim 1. In the subclaims further advantageous measures are listed, which are combined with each other Kgs ^¬ nen to achieve further advantages. Initial experimental results with oscillating, insbeson ^¬ particular sinusoidal or zigzag-shaped laser radiation show promising results with crack-free structure Struk ^¬ ture of a nickel-base superalloy.

It can by adjusting the laser power at the reversal points, in particular reduction of the laser power on

90 -6 θΠ Praax _/ a homogeneous melting depth over the width of the order-welded track in the base material can be achieved. Normally, when using non-oscillating laser radiation in laser cladding welding, maximum buildup is generated in the center of the track due to heat build-up. This can lead to columnar solidification of grains over multiple layers in heavy-weldable nickel-base superalloys, thereby promoting the initiation of critical hot cracks.

This is intended to avoid the hot cracking tendency of hard-to-weld nickel-base superalloys in laser beam build-up welding.

FIGS. 1, 2 show the schematic procedure of the method. In particular, a laser beam build-up welding with powdered filler material using a pendulum motion in the form of a sinusoidal or zigzag oscillation is performed. In this case, an adjustment of the laser processing Leis ^¬ P to the reciprocal points 16 16 ^{λ λ,} in particular with a reduction of the laser power P in particular 90% of P _m ax is performed.

As a result, a small (<150μη), homogeneous melting depth is achieved across the width of the job-welded track in the base material. This can be difficult to weld

Nickel-base superalloys avoid epitaxial growth of columnar grains over several layers, so that the risk of formation of critical hot cracks is increased. is reduced during the solidification and / or the subsequent heat treatment.

The advantages are:

 · Prevention of hot cracking during buildup welding

 hard-to-weld nickel base superalloys with a high proportion of intermetallic phase.

 • Improved material properties of the component compared to conventionally welded components.

 · Material savings, reduction of scrap rates for service components.

FIG. 1 shows the relative method of operation 13 (FIG. 2) of the energy beam, in particular of a laser beam, and FIGS

2 shows the arrangement of material flow and energy beam 7 (FIG. 2) with respect to a substrate 4. Preferably, only the energy beam, in particular the laser beam, is allowed to oscillate.

In Figure 1, the course of the oscillation, ie the deflection or deflection and the simultaneous change of the power P is plotted against the time t in milliseconds. The oscillation 13 has, as is usual with a sine curve, at least one sweeping point 16 16 ^{λ λ} , .... The sine curve is only one example of a wave-shaped movement, such as a zigzag movement, which has sweeping points 16 16 ^{λ λ} . Reaches the energy beam is laser beam 7 such a sweeping point 16 16 ^{λ λ} (max / min point), the laser power was in advance in particular continuously reduced and there ^¬ by up again, that is in the range of the sweeping point 16 16 ^{λ λ} is the laser power L shut down in advance to a lower laser power and then again in particular continuously ramped up to the original previous value P _ma x for a time t _max . t _m i _n and t _max give half the oscillation period of the sinusoid and it is preferably t _max ^ 0.3 t _m i _n ·

Only during a time period t _max is almost P _max used. Otherwise, the power P is reduced during t _m i _n .

In the best case 16 16 ^{λ λ} , ie at zero point 17, the maximum power P = P _{max is} applied in the half of two directly successive Kehrpunkte.

P _max is preferably greatest when the sinusoidal curve or oscillation passes through the zero line 17.

Preferably, only the energy beam, in particular the laser beam, oscillates.

Claims

claims

1. A method for wobbling a material application method, in particular a hardfacing,

 in particular a powder build-up welding,

 where an energy beam,

 in particular a laser beam,

 and / or material flow are moved in an oscillating manner (13) with respect to a substrate (4),

wherein the oscillatory motion has at least one sweeping point (16 ^λ , 16 ^{λ λ} ), and

wherein the power (P) of the energy beam (7) varies between the points of refraction (16 16 ^{λ λ} ),

 in particular oscillates.

2. The method according to claim 1,

in which the power (P) of the energy beam (7) is lowered before reaching the keying point (16 16 ^{λ λ} ),

 is lowered in particular continuously and

after exceeding the Kehrpunkts (16 16 ^{λ λ} ) this Leis ^¬ tion (P) of the energy beam (7) again,

 especially continuously,

 is increased.

3. The method according to claim 1 or 2,

 in which a laser deposition welding,

 in particular, a laser powder build-up welding is used,

and the material stream comprises powder.

4. The method according to one or more of claims 1, 2 or 3,

where there is a maximum power P _max ,

and the power (P) is repeatedly raised to P _max .

5. The method according to claim 4,

in which the power (P) is reduced by a maximum of at least 10%, in particular by a maximum of 50% of the maximum power (P _ma x).

6. The method according to claim 5,

in which the reduction of the power (P) corresponds to at most 30%, in particular at most 20% of the maximum power (P _ma x).

7. The method according to one or more of the preceding claims,

 in which the oscillation of energy beam and / or material flow and substrate (4) is sinusoidal.

8. The method according to one or more of the preceding claims,

 in which the oscillation of energy beam and / or material flow and substrate (4) is zigzag.

9. Method according to one or more of the preceding claims,

represent wherein _m i t _n and t _max half a period of oscillation of the Oszil ^¬ lation and it holds that t _max ^ 0.3 t _m i _n,

wherein during t _max the maximum power is used.

10. Method according to one or more of the preceding claims,

 in which only the energy beam oscillates relative to the substrate (4).

11. The method according to any one of the preceding claims 1 to 9,

 at the energy beam and material flow relative to the substrate (4) oscillate.