HARDNESS AND DIMENSIONS OF STEELS WITH HARD COATINGS PRODUCED BY CHEMICAL VAPOUR DEPOSITION AT MEDIUM TEMPERATURES

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HARDNESS AND DIMENSIONS OF STEELS WITH HARD COATINGS PRODUCED BY CHEMICAL

VAPOUR DEPOSITION AT MEDIUM TEMPERATURES

W. Ruppert

To cite this version:

W. Ruppert. HARDNESS AND DIMENSIONS OF STEELS WITH HARD COATINGS PRODUCED

BY CHEMICAL VAPOUR DEPOSITION AT MEDIUM TEMPERATURES. Journal de Physique

Colloques, 1989, 50 (C5), pp.C5-421-C5-421. �10.1051/jphyscol:1989550�. �jpa-00229580�

JOURNAL DE PHYSIQUE

Colloque C5, suppl6ment au n 0 5 , Tome 50, mai 1989

HARDNESS AND DIMENSIONS OF STEELS WITH HARD COATINGS PRODUCED BY CHEMICAL VAPOUR DEPOSITION AT MEDIUM TEMPERATURES

W . RUPPERT

M a t t e r n s t r a s s e 50, 0-6000 F r a n k f u r t am Main, F.R.G.

Chemical Vapour Deposition (CVD) of hard c o a t i n g s onto s t e e l s r e q u i r e s thorough c o n t r o l l i n g of dimensions and hardness. D i - mensional and hardness problems depend on t h e m e t a l l u r g i c a l p r o p e r t i e s of t h e base and t h e h e a t t r e a t m e n t s which a r e ap- p l i e d t o t h e s t e e l b e f o r e and a t t h e a p p l i c a t i o n o f CVD. Some i n f o r m a t i o n on t h e c o n t r o l of t h e dimensions and t h e hardness of high-carbon high-chromium t o o l s t e e l s which have t o be coa- t e d w i t h hard compounds by CVD a t h i g h t e m p e r a t u r e s (HTCVD) was a l r e a d y p r e s e n t e d some y e a r s ago ( I ) .

The paper which i s now proposed w i l l d e a l w i t h some dimensio- n a l and hardness problems which a r e connected t o t h e produc- t i o n of h a r d c o a t i n g s on t o o l s t e e l s by means of CVD a t medium t e m p e r a t u r e s (MTCM). Such p r o c e s s e s a r e u s u a l l y a p p l i e d t o t o o l s which have been a l r e a d y h e a t t r e a t e d ( a t l e a s t quenched and tempered ) and f i n a l l y worked (ground and p o l i s h e d ) . Thus MTCVD i n v o l v e s an a d d i t i o n a l h e a t t r e a t m e n t (tempering) and may provoke m e t a l l u r g i c a l r e a c t i o n s i n t h e base which cause changes i n dimensions and hardness.

S t a r t i n g w i t h some components i n t h e m i c r o s t m c t u r e of s t e e l s and t h e i r s p e c i f i c volumes, an i n t r o d u c t i o n i n t o t h e dimensio- n a l changes of s t e e l s due t o hardening, temperihg and subcoo- l i n g w i l l be presented. The d i m e n s i o n a l ~ s t a b i l i t y of s t e e l s depends predominantly on t h e r e t a i n e d a u s t e n i t e and t h e degree of s u p e r s a t u r a t i o n w i t h a l l o y i n g elements.

The hardness of high-carbon high-chromium t o o l s t e e l s w i l l be d i s c u s s e d by means of s p a t i a l diagramms which show t h e hard- n e s s IN30 as a f u n c t i o n of a u s t e n i t i z i n g temperature Ta and tempering temperature Tt a t c o n s t a n t tempering time t t , and a l s o a s a f u n c t i o n of Ta and tt a t c o n s t a n t Tt. The i n f l u e n c e of m u l t i p l e tempering w i l l be d i s c u s s e d w i t h r e s p e c t t o t h e a p p l i c a t i o n of MTCVD.

( 1)

. Ruppert, W ; Thin S o l i d Films, 40 (19771 27

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Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1989550